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Eclipse 100 User Course Page 101 of 499 08/04/99
The vi Editor
Insert Mode
a append after cursor
A append at end of line
i insert before cursor
I insert at beginning of line
o open a line below current line
O open a line above current line
s substitute a character
S substitute entire line
Movement Commands: Characters
h, j, k, l left, down, up, right
Movement Commands: Text
w, W, b, B forward ,backward, by word
e, E end of word
),( beginning of next, current sentence
},{ beginning of next, current paragraph
]],[[ beginning of next, correction section
Movement Commands: Lines
0,$ first, last position of current line
+. - first character of next, previous line
RETURN first character of next line
n | column n of current line
H top line of screen
M middle line of screen
L last line of screen
Searches
/text search forward for text
n repeat previous search
N repeat search in opposite direction
/ repeat forward search
? repeat previous search backward](https://image.slidesharecdn.com/e100manual-140526002505-phpapp02/85/E100-manual-101-320.jpg)
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Eclipse 100 User Course Page 137 of 499 08/04/99
Transmissibility Conventions
Transmissibility is a property shared between connected cells, i.e. cells between which
fluids may flow. In a system of discrete grid cells fluid flow is calculated between the
centres of the grid blocks. The extent of this flow is determined by the transmissibility
and mobility between connected cells, and how those quantities are calculated and
assigned.
Consider the flow between two adjacent cell centres. The transmissibility must account
for the cell properties in each cell i.e. it has to be some form of average of the properties
of both cells which also accounts for the cell geometry and overlapping area. The
variations on transmissibility calculation used by ECLIPSE are described in the
following sections. Some are more appropriate for certain types of geometry than
others. All transmissibility calculations, however, are in the upstream direction i.e. the
transmissibilities assigned to cell (I, J, K) govern the flows to cells (I+1, J, K), (I, J+1,
K) and I, J, K+1).
NOTE. The assignment of mobility between adjacent cells does not follow the same
convention. In calculating the mobility for flow between two cells the available
mobilities are of the current cell, the upstream cell and an average of the two. Of these,
the upstream mobility has been found to be the most reliable [1]. This is superficially
counter-intuitive because the mobility used should be the average mobility of the fluid
flowing between the blocks at any particular time. By Darcy’s Law for each phase,
however, this fluid comes from the block with the larger phase potential. Use of the
upstream mobility assumes that the upstream block contains “stirred” fluid so that the
mobility of fluid travelling across the cell interface is the same as the mobility of the
fluid at the cell centre. Mattax, C. C., Dalton, R. L., “Reservoir Simulation”, SPE
Monograph v.13[2]](https://image.slidesharecdn.com/e100manual-140526002505-phpapp02/85/E100-manual-137-320.jpg)
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Cartesian Grid Transmissibility
The transmissibility between a pair of connected cells is calculated from the cell
geometry, permeability and net to gross. The simplest methods are to calculate the
flows between two neighbouring cells by considering either the flow between the cell
centres (at which the cell properties are averaged) or by integrating the phase potential
between two chosen locations. The result is then compared to Darcy’s equation and the
portion analogous to KA/L extracted. Depending on the available information on cell
geometry and averaging method, one of a number of different calculation methods may
be used.
NOTE. A detailed exposition on the derivation of transmissibility of Cartesian grid
systems can be found in reference .[3]
OLDTRAN Transmissibility Calculation
Figure 44: OLDTRAN transmissibility definition
OLDTRAN is used by default in block centred models. It takes the form
DX1 DX2
DZ1
DZ2
Kx1
and NTG1
KX2 and NTG2
A2=DY2.DZ2
(DX1+DX2)/2
T12
Depth D2
Depth D1
A1=DY1.DZ1](https://image.slidesharecdn.com/e100manual-140526002505-phpapp02/85/E100-manual-139-320.jpg)
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Eclipse 100 User Course Page 257 of 499 08/04/99
Three-Phase Relative Permeability
Eclipse Default
The ECLIPSE default three-phase relative permeability calculation is a weighted sum of
the two-phase relative permeabilities. It assumes full segregation of fluids within the
cell. Although this is rare, the model is robust and has been used extensively and found
adequate.
Modified STONE1
An alternative three-phase relative permeability model available in ECLIPSE is a
modification of the first model suggested by Stone in 1970 [4]. The STONE keyword
activates this calculation. A more comprehensive explanation can be found in the
ECLIPSE 100 TECHNICAL APPENDICES.
Modified STONE2
The third three phase relative permeability calculation option available in ECLIPSE is a
modification of Stone’s second model proposed in [5]. The STONE2 keyword activates
this calculation.
The STONE2 method may produce negative values of oil relative permeability. In this
event, ECLIPSE resets the calculated value to zero. A more comprehensive explanation
can be found in the ECLIPSE 100 TECHNICAL APPENDICES.](https://image.slidesharecdn.com/e100manual-140526002505-phpapp02/85/E100-manual-257-320.jpg)
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Eclipse 100 User Course Page 336 of 499 08/04/99
Carter-Tracy Aquifers
Figure 113: Carter-Tracy aquifer definition
• Carter-Tracy aquifers are defined in the SOLUTION section.
• The aquifer properties are defined by the AQCT keyword
• The pressure response is defined by an influence function, which may be entered
with the AQUTAB keyword.
• Carter-Tracy aquifers are attached to the oil zone by NNCs defined in the AQUANCON
keyword
• The total number of analytical aquifers and aquifer NNCs is defined in AQUDIMS in
RUNSPEC
• Fetkovich and Carter-Tracy aquifers cannot be used in the same run
a
tw
c
kc
rC
T
1
2
0φµ
=
The main parameters governing
Carter-Tracy aquifer behaviour are
the time constant Tc
, which is t/tD ,
and the aquifer influx constant β.
2
02 rChc tθφβ =
The pressure drop at the aquifer
boundary is
)(0 DD
a
a tP
Q
PP
β
=−
( ) ( )[ ]{ }tPittPibaQ iai −∆+−=α
and the average flow rate to cell i
from time t to t+∆t is
To define Carter-Tracy aquifers use
RUNSPEC
AQUDIMS
SOLUTION
AQUCT
AQUTAB
AQUANCON
Influence
Function](https://image.slidesharecdn.com/e100manual-140526002505-phpapp02/85/E100-manual-336-320.jpg)
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Eclipse 100 User Course Page 398 of 499 08/04/99
positive it will over-ride the saturation table set in COMPDAT. If zero, the saturation table
of the connecting cell will be used. If negative (which is the default) the saturation table
specified in COMPDAT will be used.
CVEFRAC
This is the fraction of Vertical Equilibrium curves to be used in calculating relative
permeabilities for the connection
DTOP.
Top depth of the top connection in the set matching the location indices in items 2-5.
DBOT.
Bottom depth of the bottom connection in the set matching the location indices in items
2-5.
Flag to re-calculate the skin factor taking account of partial penetration.
• NO is the default; the skin factor set in COMPDAT will be used
• YES The skin factor will be calculated from Odeh’s correlation and will be used in
place of that supplied in COMPDAT; the connection transmissibility will then be re-
calculated.
The well bore diameter must be set in COMPDAT. The skin factor and transmissibility will
be recalculated every time a plug-back takes place.
In cases of partial penetration the convergence of the fluid flow lines towards the
perforated interval is different from the case of total penetration. This can be treated as
an additional component of the skin factor. For a well subject to partial penetration the
total mechanical skin factor is
pd
p
t
SS
h
h
S +=
EQ. 79
where
ht is the formation thickness
hp is the perforation interval
Sd is the damage skin factor
Sp is the partial penetration skin factor
Sp is calculated from a correlation .[6]](https://image.slidesharecdn.com/e100manual-140526002505-phpapp02/85/E100-manual-398-320.jpg)
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Eclipse 100 User Course Page 399 of 499 08/04/99
( ) ( )[ ] ( ){ }wctprtpr rhh
hp
ht
Sp lnln1.049.095.17ln135.1
825.0
+−−+
−=
EQ. 80
Where
h
v
t
tpr
K
K
h
h =
EQ. 81
+= 753.22126.0exp
t
m
wwc
h
z
rr
EQ. 82
zm is the distance between the middle of the perforated interval and the top or bottom
of the formation, whichever is nearer
rw is the wellbore radius
All lengths are specified in feet. The connection factor is the derived using the new
value of the skin factor. As partial penetration effects are contained in the new skin
factor, the effective Kh should be based on the formation thickness ht, not the
perforation interval hp.
If the formation is divided vertically into two or more layers of grid blocks the skin
factor is calculated separately for each completed layer. Then
GTOPGBOTht −=
EQ. 83
DTOPDBOThp −=
EQ. 84
( ) ( ){ }DBOTDTOPGBOTGTOPDBOTDTOPMINzm +−−+= 5.0,5.0
EQ. 85
Sd the damage skin factor.
This defaults to zero.
GTOP.
Depth of the top of the grid cell at the position of the well connection. This is only
relevant if the skin factor is to be recalculated for partial penetration and the well is](https://image.slidesharecdn.com/e100manual-140526002505-phpapp02/85/E100-manual-399-320.jpg)
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Eclipse 100 User Course Page 498 of 499 08/04/99
REFERENCES
[1] Huppler, J. D.: “Numerical Investigation of the Effects of Core Heterogeneities on Waterflood Relative
Permeabilities”, SPEJ (Dec 1970) 381-92; Trans., AIME, 249 135
[2] Mattax, C. C., Dalton, R. L: “Reservoir Simulation”, SPE Monograph v.13, 1990 135
[3] Mattax, C. C., Dalton, R. L., “Reservoir Simulation”, SPE Monograph v.13, 1990 137
[4] Stone; Trans AIME, 249, 1970, pp.214-218 255
[5] Stone; J. Can. Pet. Tech., 12, 1973, 53-61 255
[6] Odeh. J. Pet. Tech. 1980, p.964 392
[7] M. Munoz, Eclipse 100 User Course passim 397](https://image.slidesharecdn.com/e100manual-140526002505-phpapp02/85/E100-manual-498-320.jpg)
Uploaded byAndres Barragan
E100 manual
This document provides an introduction to the Eclipse reservoir simulation software. It describes the purpose and functionality of Eclipse, outlines the basic workflow and file structure for Eclipse simulations, and provides detailed explanations of each input data section including GRID, EDIT, PROPS, REGIONS, SOLUTION, and SCHEDULE. The document also discusses convergence troubleshooting and includes exercises for building and running simple Eclipse models.
E100 manual
- 1. ECLIPSE 100 USERCOURSE
- 2. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 2 of 499 08/04/99 CONTENTS Introduction...........................................................................................................................................................13 Purpose .............................................................................................................................................................14 What is Reservoir Simulation...........................................................................................................................16 How Does the Model Relate to the Reservoir ..................................................................................................18 Why Reservoir Simulation?..............................................................................................................................22 Why ECLIPSE?................................................................................................................................................24 ECLIPSE Features............................................................................................................................................26 How ECLIPSE Works......................................................................................................................................28 Static Reservoir Description.............................................................................................................................32 PVT and Rock Data..........................................................................................................................................36 Initialisation Data..............................................................................................................................................38 Equilibration.................................................................................................................................................39 Enumeration .................................................................................................................................................39 Restart Runs .................................................................................................................................................39 Well Data..........................................................................................................................................................42 Reservoir Simulation with ECLIPSE ...............................................................................................................44 How to Use the Manuals...................................................................................................................................46 File Organisation and Structure ............................................................................................................................49 ECLIPSE Input / Output Structure ...................................................................................................................50 ECLIPSE Output Files......................................................................................................................................52 ECLIPSE Output Styles....................................................................................................................................56 Output File Names............................................................................................................................................60 File Extensions and Case..............................................................................................................................61 How to Alter Personal Default File Extensions and Case ............................................................................62 Output Styles................................................................................................................................................63 File Locations ...................................................................................................................................................64 Utility Macros...................................................................................................................................................66 @convert ......................................................................................................................................................67 @copyconfig ................................................................................................................................................67 @ecl2avs ......................................................................................................................................................67 @expand.......................................................................................................................................................67 @extract .......................................................................................................................................................67 @flexstart.....................................................................................................................................................67 @frame.........................................................................................................................................................67 @lmdown.....................................................................................................................................................68 @lmhostid ....................................................................................................................................................68 @lmstat ........................................................................................................................................................68 Input Data File Structure ..................................................................................................................................70 Data File Syntax ...............................................................................................................................................74 Keyword Syntax ...............................................................................................................................................76 Any Section Keywords.....................................................................................................................................80 INCLUDE ....................................................................................................................................................81 COLUMNS ..................................................................................................................................................81 DEBUG........................................................................................................................................................81 NOECHO .....................................................................................................................................................81 ECHO...........................................................................................................................................................81 EXTRAPMS.................................................................................................................................................81 OPTIONS.....................................................................................................................................................81 MESSAGES.................................................................................................................................................81 NOWARN....................................................................................................................................................82 FORMFEED.................................................................................................................................................82 LOAD...........................................................................................................................................................82 The RUNSPEC Section ........................................................................................................................................83 Purpose of the RUNSPEC Section ...................................................................................................................84 How to Convert Fixed Format RUNPSEC to Free Format ..........................................................................86 RUNSPEC Keywords and Switches.................................................................................................................88 Commonly used RUNSPEC keywords and switches...................................................................................89
- 3. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 3 of 499 08/04/99 Data Files with No RUNSPEC.........................................................................................................................92 How to Create a Fast Restart........................................................................................................................93 System Usage........................................................................................................................................................95 Basic Unix Commands .....................................................................................................................................96 The vi Editor...................................................................................................................................................100 The GRID Section...............................................................................................................................................105 Purpose of the GRID Section..........................................................................................................................106 Data Reading Convention...............................................................................................................................110 Cartesian Grids...........................................................................................................................................110 Radial Grids................................................................................................................................................110 Geometrical Representations..........................................................................................................................114 Block Centred Geometry............................................................................................................................115 Corner Point Geometry ..............................................................................................................................116 Corner Point versus Block Centred Geometry ...........................................................................................117 Block-Centred Geometry Example.................................................................................................................118 Corner Point Geometry Example....................................................................................................................122 Grid Cell Properties........................................................................................................................................124 How to Assign Grid Cell Properties ...............................................................................................................126 How to Set One Property Value per Grid Cell ...........................................................................................127 How to Set Grid Cell Property Values Using Boxes..................................................................................128 How to Set Grid Cell Property Values Using EQUALS ............................................................................128 How to Copy Grid Cell Property Data .......................................................................................................130 How to Add, Subtract, Multiply and Divide Grid Cell Property Data .......................................................131 How to Multiply Cell Pore Volume Using MULTPV................................................................................132 How to Copy Data From one Portion of the Grid to Another using COPYBOX.......................................132 How to Read Data from Another File Using INCLUDE............................................................................133 How to Deactivate Cells Using ACTNUM ................................................................................................133 Transmissibility Conventions .........................................................................................................................136 Cartesian Grid Transmissibility......................................................................................................................138 OLDTRAN Transmissibility Calculation...................................................................................................139 OLDTRANR Transmissibility Calculation................................................................................................142 NEWTRAN Transmissibility Calculation..................................................................................................144 Radial Grid Transmissibility...........................................................................................................................146 Shale Modelling..............................................................................................................................................150 Modelling shales explicitly as grid layers ..................................................................................................151 Modelling shales by incorporation into larger sand cells ...........................................................................151 Modelling shales as gaps between sand layers...........................................................................................152 Transmissibility Modification.........................................................................................................................154 Non-Neighbour Connections..........................................................................................................................160 NNC Generation across Faults .......................................................................................................................162 NNC Generation across Pinchouts .................................................................................................................164 NNC Generation at Local Grid Refinements..................................................................................................166 NNCs in Dual Porosity Models ......................................................................................................................168 NNC Generation in Aquifers..........................................................................................................................170 NNC Generation in Radial Models.................................................................................................................172 Radial Models.................................................................................................................................................174 Output Control................................................................................................................................................178 GRIDFILE..................................................................................................................................................179 NOGGF......................................................................................................................................................179 INIT............................................................................................................................................................179 RPTGRID...................................................................................................................................................179 BOUNDARY .............................................................................................................................................180 Grid Section Keyword Summary....................................................................................................................182 Cartesian Geometry....................................................................................................................................183 Radial Geometry.........................................................................................................................................183 Cell Properties............................................................................................................................................183 Pinchouts & Deactivation...........................................................................................................................184 Transmissibility..........................................................................................................................................184 Transmissibility modification.....................................................................................................................184 Faults..........................................................................................................................................................184 Diffusivity ..................................................................................................................................................185
- 4. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 4 of 499 08/04/99 Numerical Aquifers....................................................................................................................................185 Operators....................................................................................................................................................185 Dual Porosity / Permeability ......................................................................................................................185 Flux Boundary Option................................................................................................................................186 Independent Reservoir Regions..................................................................................................................186 Thermal Option ..........................................................................................................................................186 Vertical Equilibrium Option.......................................................................................................................186 Miscellaneous and Output..........................................................................................................................186 The EDIT Section ...............................................................................................................................................189 Purpose of the EDIT Section ..........................................................................................................................190 Edit Section Keyword Summary ....................................................................................................................192 The PROPS Section – Fluid Properties...............................................................................................................195 Purpose of Fluid Properties.............................................................................................................................196 Black Oil Overview........................................................................................................................................198 Black oil versus compositional simulation .....................................................................................................202 The Oil Equation of State ...............................................................................................................................204 Dead Oil PVT Data Entry Using PVDO.........................................................................................................208 Dead Oil PVT Data Entry Using PVCDO......................................................................................................210 Live Oil PVT Data Entry Using PVTO..........................................................................................................212 Live Oil PVT Data Entry Using PVCO..........................................................................................................214 The Gas Equation of State ..............................................................................................................................216 Dry Gas Data entry Using PVZG ...................................................................................................................220 Dry Gas PVT Data Entry Using PVDG..........................................................................................................222 Wet Gas PVT Data Entry Using PVTG..........................................................................................................224 The Water Equation of State...........................................................................................................................226 Reference Densities ........................................................................................................................................228 Black Oil Model Phase Options......................................................................................................................230 Three-phase simulations.............................................................................................................................231 Two-phase simulations...............................................................................................................................231 Single phase simulations ............................................................................................................................232 Defining Multiple PVT Types using PVT Regions........................................................................................234 How to define multiple PVT types using PVT regions ..............................................................................235 Defining Multiple PVT Types using API Tracking........................................................................................238 How to Implement API Tracking...............................................................................................................239 Example API Tracking Data ......................................................................................................................240 Rock Compressibility .....................................................................................................................................244 Saturation Functions and Endpoint Scaling ........................................................................................................247 Purpose of Saturation Functions.....................................................................................................................248 Saturation Functions.......................................................................................................................................250 Saturation Function Definition...................................................................................................................251 Saturation Function Keyword Family 1 .....................................................................................................252 Saturation Function Keyword Family 2 .....................................................................................................253 Three-Phase Relative Permeability.................................................................................................................256 Eclipse Default ...........................................................................................................................................257 Modified STONE1 .....................................................................................................................................257 Modified STONE2 .....................................................................................................................................257 Saturation Function Scaling............................................................................................................................258 Endpoint Scaling.............................................................................................................................................260 How to Implement Endpoint Scaling .........................................................................................................261 2-Point and 3-Point Endpoint Scaling ........................................................................................................263 Limiting three-Point Endpoint Scaling.......................................................................................................264 Vertical scaling...............................................................................................................................................266 Capillary Pressure Scaling..............................................................................................................................270 Vertical Capillary Pressure Scaling............................................................................................................271 Horizontal Capillary Pressure Scaling........................................................................................................271 The Leverett J Function..............................................................................................................................271 Pressure Dependent Interfacial Tension.....................................................................................................272 Output Control................................................................................................................................................274 The REGIONS Section .......................................................................................................................................277 Purpose of the REGIONS Section..................................................................................................................278 Regions Keyword Types.................................................................................................................................280
- 5. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 5 of 499 08/04/99 Region definition keywords .......................................................................................................................281 Fluid in Place Regions................................................................................................................................282 Directional Keywords.................................................................................................................................283 Operators....................................................................................................................................................283 Output Controls..........................................................................................................................................283 The SOLUTION Section ....................................................................................................................................285 Purpose of the SOLUTION Section ...............................................................................................................286 Equilibration...................................................................................................................................................288 Initial Phase Saturation...............................................................................................................................289 Initial Phase Saturation in the Transition Zone ..........................................................................................290 EQUIL Keyword Usage..................................................................................................................................292 Block Centre Equilibration.............................................................................................................................294 Level and Tilted Block Fine Grid Equilibration.............................................................................................296 Quiescence .................................................................................................................................................297 Mobile Fluid Correction .................................................................................................................................300 Transition Zone Endpoint Variation...............................................................................................................304 Matching Initial Water Distribution ...............................................................................................................306 Enumeration....................................................................................................................................................308 Initial Solution Ratios.....................................................................................................................................310 Restarts ...........................................................................................................................................................312 How to Create a Full Restart Run...............................................................................................................315 How to Create a Fast Restart Run ..............................................................................................................316 Flexible vs. Fast Restarts............................................................................................................................317 Output Control................................................................................................................................................320 Aquifer Modelling...............................................................................................................................................323 Aquifer Modelling Facilities...........................................................................................................................324 Grid Cell Aquifers ..........................................................................................................................................326 Numerical Aquifers ........................................................................................................................................328 Fetkovich Aquifers .........................................................................................................................................332 Carter-Tracy Aquifers.....................................................................................................................................336 Flux Aquifers..................................................................................................................................................340 Output Control................................................................................................................................................342 The SUMMARY Section....................................................................................................................................345 Purpose of the SUMMARY Section...............................................................................................................346 Additional Parameters ....................................................................................................................................350 Field quantities...........................................................................................................................................351 Region quantities........................................................................................................................................351 Group quantities .........................................................................................................................................351 Well quantities............................................................................................................................................351 Block quantities..........................................................................................................................................351 Connection quantities.................................................................................................................................352 Output Controls and Additional Keywords ....................................................................................................354 Anisotropic relative permeability keywords...............................................................................................355 Reservoir Volumes.....................................................................................................................................355 Oil Recovery Efficiencies...........................................................................................................................355 Oil Recovery Mechanisms .........................................................................................................................355 Analytic Aquifer Quantities .......................................................................................................................355 Brine Option Keywords..............................................................................................................................355 Simulator Performance Keywords .............................................................................................................356 Output Control Keywords ..........................................................................................................................356 The SCHEDULE Section – History Matching....................................................................................................357 Purpose of the SCHEDULE Section ..............................................................................................................358 History Matching Versus Prediction...............................................................................................................360 History Matching........................................................................................................................................361 Prediction ...................................................................................................................................................361 History Match SCHEDULE Section Structure...............................................................................................364 VFP Curve Specification ................................................................................................................................368 VFP Table Generation................................................................................................................................369 Production Well VFP Table Structure........................................................................................................370 Injection Well VFP Table Structure...........................................................................................................370 Pipeline Segment VFP Table Structure......................................................................................................371
- 6. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 6 of 499 08/04/99 VFP Table Usage in ECLIPSE...................................................................................................................371 How to Set up VFP Tables in Eclipse ........................................................................................................372 Drilling a Well: WELSPECS..........................................................................................................................374 Gas Flow in Wells ..........................................................................................................................................380 Low Pressure gas wells ..............................................................................................................................381 The Russel Goodrich Equation...................................................................................................................381 The Gas Pseudopressure.............................................................................................................................382 Standard Inflow Equation...........................................................................................................................383 Connection Specification: COMPDAT ..........................................................................................................384 Partial Completion: COMPRP........................................................................................................................392 Partial Completion with VE: COMPVE.........................................................................................................396 Measured Well Production Rates: WCONHIST ............................................................................................402 Well Injection Rates: WCONINJE.................................................................................................................406 Simulator Control: TUNING, TUNINGL and NEXTSTEP...........................................................................410 Output Control : RPTSCHED and RPTRST ..................................................................................................414 Re-Solution and Re-Evaporation Rates: DRSDT & DRVDT ........................................................................418 Simulation Advance and Termination: DATES, TSTEP & END ..................................................................420 Well Performance Matching...........................................................................................................................422 Productivity Index Adjustment...................................................................................................................423 Drawdown Adjustment...............................................................................................................................424 Manual Workovers, Rate and PI Modifications..............................................................................................426 Manually Opening and Shutting Wells or Connections: WELOPEN ........................................................427 Completion Workovers: COMPDAT.........................................................................................................427 Partially Penetrated Completion Workovers: COMPRP, COMPVE .........................................................427 Modifying Well Targets: WELTARG........................................................................................................427 Well Pi Modification: WELPI and WPIMULT..........................................................................................428 Modelling Well Stimulation by means other than Skin Factor Change .....................................................428 The SCHEDULE Section – Prediction ...............................................................................................................431 Prediction SCHEDULE Section Structure......................................................................................................432 Setting Well Target Rates: WCONPROD ......................................................................................................436 Economic Limit Definition.............................................................................................................................440 Well Economic Limits, Automatic Workovers and Cutbacks........................................................................442 Well Economic Limits................................................................................................................................443 Connection Economic Limits: CECON .....................................................................................................444 Plugging Wells Back: WPLUG..................................................................................................................445 Workovers using WLIFT ...........................................................................................................................446 Well Testing: WTEST................................................................................................................................447 Cutting Wells Back: WCUTBACK............................................................................................................448 Group Control.................................................................................................................................................450 Creating a Group Hierarchy: GRUPTREE.................................................................................................452 Group / Field Production Control: GCONPROD ...........................................................................................454 Production Target Infringements................................................................................................................455 Solution Method.........................................................................................................................................456 Group Injection Control: GCONINJE ............................................................................................................458 Surface Injection Rate ................................................................................................................................459 Reservoir Volume Injection Rate ...............................................................................................................459 Re-injection................................................................................................................................................459 Voidage Replacement.................................................................................................................................459 Priority Control...............................................................................................................................................462 Group Economic Limits: GECON..................................................................................................................464 Convergence .......................................................................................................................................................467 Typical Convergence Problems......................................................................................................................468 Data Error...................................................................................................................................................469 PVT Table Errors .......................................................................................................................................469 VFP Table Errors .......................................................................................................................................470 Saturation Table Errors ..............................................................................................................................470 Typographic Errors ....................................................................................................................................471 Missing values............................................................................................................................................471 Special Characters......................................................................................................................................471 Model Design.............................................................................................................................................472 Grid Geometry............................................................................................................................................472
- 7. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 7 of 499 08/04/99 LGR Design................................................................................................................................................472 Program defects..........................................................................................................................................472 Eclipse 100 User Course Exercises.....................................................................................................................474 Exercise 1: Single Well Coning Model ..........................................................................................................475 Exercise 2: Sector Model RUNSPEC Section................................................................................................479 Exercise 3: Sector Model GRID Section ........................................................................................................481 Exercise 4: Sector Model PROPS and REGIONS Sections ...........................................................................485 Exercise 5: Sector Model Initialisation...........................................................................................................487 Exercise 6: Sector Model History Match........................................................................................................491 Exercise 7: Sector Model Recovery Optimisation..........................................................................................495 References...........................................................................................................................................................498
- 8. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 8 of 499 08/04/99 LIST OF FIGURES Figure 1: ECLIPSE User Course Structure...........................................................................................................14 Figure 2: Material Balance Applied to Reservoir Simulation...............................................................................16 Figure 3: Reservoir Description versus Simulation Model ...................................................................................18 Figure 4: Role of Simulation.................................................................................................................................22 Figure 5: Role of ECLIPSE...................................................................................................................................24 Figure 6: ECLIPSE 100 and 200 Features ............................................................................................................26 Figure 7: Principal Simulator Activities................................................................................................................28 Figure 8: Simulation Grid Data Requirements......................................................................................................32 Figure 9: PVT and Rock Data Requirements........................................................................................................36 Figure 10: Initialisation Data Requirements .........................................................................................................38 Figure 11: Well flow rates and monthly averages as viewed using Schedule.......................................................42 Figure 12: Simplified Stages of a Full Field Simulation Study.............................................................................44 Figure 13: How to use the ECLIPSE documentation............................................................................................46 Figure 14: Relationship of Eclipse and pre-and post-processors ..........................................................................50 Figure 15: Eclipse outputs.....................................................................................................................................52 Figure 16: Available Eclipse output types ............................................................................................................56 Figure 17: Eclipse filenames for each output style part 1 .....................................................................................60 Figure 18: Eclipse filenames for each output style part 2 .....................................................................................62 Figure 19: Setting Personal File Extensions and Cases.........................................................................................63 Figure 20: Eclipse and related software file locations...........................................................................................64 Figure 21: Eclipse suite utility macros..................................................................................................................66 Figure 22: Major sections of the Eclipse input data file........................................................................................70 Figure 23: Summary of data file syntax................................................................................................................74 Figure 24: Syntax of Eclipse keywords.................................................................................................................76 Figure 25: Keywords for any section....................................................................................................................80 Figure 26: Minimum RUNSPEC options..............................................................................................................84 Figure 27: Eclipse 100 RUNSPEC keywords in alphabetical order .....................................................................88 Figure 28: Fast Restart File Structure ...................................................................................................................92 Figure 29: The console..........................................................................................................................................96 Figure 30: The vi device-independent editor ......................................................................................................100 Figure 31: Minimum GRID section contents......................................................................................................106 Figure 32: Grid data reading convention.............................................................................................................110 Figure 33: Radial data reading convention .........................................................................................................112 Figure 34: Block-centred and corner-point geometries.......................................................................................114 Figure 35: Sloping structure with fault represented in block centred geometry..................................................115 Figure 36: Sloping structure with fault represented in corner point geometry....................................................116 Figure 37: Example block-centred geometrical representation...........................................................................118 Figure 38: Example corner-point geometrical representation.............................................................................122 Figure 39: Grid cell property definition ..............................................................................................................124 Figure 40: Inputting grid data .............................................................................................................................126 Figure 41: Copying, Adding and Multiplying Data ............................................................................................130 Figure 42: Transmissibility conventions.............................................................................................................136 Figure 43: Cartesian grid transmissibility as viewed using GRAF .....................................................................138 Figure 44: OLDTRAN transmissibility definition ..............................................................................................139 Figure 45: Effect of uneven block sizes in BC geometry....................................................................................141 Figure 46: OLDTRANR transmissibility definition ...........................................................................................142 Figure 47: NEWTRAN transmissibility definition .............................................................................................144 Figure 48: Radial transmissibility .......................................................................................................................146 Figure 49: Shale representation...........................................................................................................................150 Figure 50: Modifying transmissibility using MULTX, FAULTS and MULTFLT.............................................154 Figure 51: Sources of non-neighbour connections..............................................................................................160 Figure 52: Fault non-neighbour connections.......................................................................................................162 Figure 53: Pinchout NNC generation..................................................................................................................164 Figure 54: LGR NNC generation........................................................................................................................166 Figure 55: NNC generation in dual porosity models...........................................................................................168 Figure 56: Aquifer non-neighbour connections ..................................................................................................170 Figure 57: Completing the circle in a radial model.............................................................................................172
- 9. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 9 of 499 08/04/99 Figure 58: Radial model geometry......................................................................................................................174 Figure 59: Grid Section Output Control..............................................................................................................178 Figure 60: Grid section keyword summary.........................................................................................................182 Figure 61: Purpose of the EDIT section..............................................................................................................190 Figure 62: EDIT section keyword summary.......................................................................................................192 Figure 63: Purpose of fluid property data ...........................................................................................................196 Figure 64: Generalised two-phase PVT envelope...............................................................................................198 Figure 65: Steps taken in black oil and compositional simulations ....................................................................202 Figure 66: Oil equation of state for the black oil model......................................................................................204 Figure 67: Dead oil PVT data entry using PVDO...............................................................................................208 Figure 68: Dead oil PVT data entry using PVCDO ............................................................................................210 Figure 69: Live oil PVT data entry with PVTO..................................................................................................212 Figure 70: Live oil PVT data entry with PVCO..................................................................................................214 Figure 71: Gas equation of state for the black oil model ....................................................................................216 Figure 72: Dry Gas Data Entry Using PVZG......................................................................................................220 Figure 73: Dry gas PVT using PVDG.................................................................................................................222 Figure 74: Wet gas PVT data using PVTG.........................................................................................................224 Figure 75: The water equation of state................................................................................................................226 Figure 76: Reference densities............................................................................................................................228 Figure 77: Black oil phase options......................................................................................................................230 Figure 78: Two oil types modelled using distinct PVT regions..........................................................................234 Figure 79: API tracking keywords and initial oil API.........................................................................................238 Figure 80: Rock compressibility.........................................................................................................................244 Figure 81: Required saturation function data for the PROPS section .................................................................248 Figure 82: Saturation function keyword families................................................................................................250 Figure 83: Default three-phase oil relative permeability calculation ..................................................................256 Figure 84: Significant saturation endpoints ........................................................................................................258 Figure 85: Effect of saturation scaling................................................................................................................260 Figure 86: Two-Point and Three-Point Endpoint Scaling...................................................................................263 Figure 87: SCALELIM keyword effect ..............................................................................................................264 Figure 88: Vertical saturation function scaling...................................................................................................266 Figure 89: Capillary pressure scaling..................................................................................................................270 Figure 90: PROPS section output control ...........................................................................................................274 Figure 91: Example REGIONS section data.......................................................................................................278 Figure 92: REGIONS Section Keywords............................................................................................................280 Figure 93: Function of the SOLUTION section..................................................................................................286 Figure 94: Block centre equilibration..................................................................................................................288 Figure 95: EQUIL keyword parameters..............................................................................................................292 Figure 96: Block Centre Equilibration................................................................................................................294 Figure 97: Level and Tilted Block Equilibration ................................................................................................296 Figure 98: Mobile Fluid Correction ....................................................................................................................300 Figure 99: Transition Zone Endpoint Variation..................................................................................................304 Figure 100: Matching Initial Water Distribution ................................................................................................306 Figure 101: Initial conditions defined by enumeration .......................................................................................308 Figure 102: Initial solution ratios........................................................................................................................310 Figure 103: History matching restart runs...........................................................................................................312 Figure 104: Multiple restarts during prediction ..................................................................................................314 Figure 105: Steps in creating a full restart run....................................................................................................315 Figure 106: Steps in creating a fast restart ..........................................................................................................316 Figure 107: SOLUTION section output control..................................................................................................320 Figure 108: Aquifer definition ............................................................................................................................324 Figure 109: Grid cell aquifer definition ..............................................................................................................326 Figure 110: Numerical aquifer definition............................................................................................................328 Figure 111: Model instability from poor aquifer design .....................................................................................330 Figure 112: Fetkovich aquifer definition ............................................................................................................332 Figure 113: Carter-Tracy aquifer definition........................................................................................................336 Figure 114: Flux aquifer definition.....................................................................................................................340 Figure 115: Output control..................................................................................................................................342 Figure 116: SUMMARY Section Purpose..........................................................................................................346 Figure 117: Additional SUMMARY mnemonic parameters ..............................................................................350 Figure 118: SUMMARY section output control keywords ................................................................................354
- 10. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 10 of 499 08/04/99 Figure 119: SCHEDULE section contents..........................................................................................................358 Figure 120: History matching and prediction regimes........................................................................................360 Figure 121: History match dataset structure........................................................................................................364 Figure 122: VFP curve specification...................................................................................................................368 Figure 123: VFP table usage in Eclipse ..............................................................................................................371 Figure 124: General well specification ...............................................................................................................374 Figure 125: Flow in gas wells .............................................................................................................................380 Figure 126: Specifying connections using COMPDAT......................................................................................384 Figure 127: Rescaling saturation tables at well connections: COMPRP.............................................................392 Figure 128: Partial completions in VE and diffuse flow models: COMPVE......................................................396 Figure 129: Historical rate specification using WCONHIST..............................................................................402 Figure 130: Setting injection rate using WCONINJE .........................................................................................406 Figure 131: Setting convergence criteria using TUNING and TUNINGL .........................................................410 Figure 132: Output control using RPTSCHED...................................................................................................414 Figure 133: Effect of zero gas re-solution rate DRSDT......................................................................................418 Figure 134: Simulation advance and termination................................................................................................420 Figure 135: Physical and Eclipse Models of Production Wells ..........................................................................422 Figure 136: Measures of Pressure in the Vicinity of a Well ...............................................................................425 Figure 137:A selection of manual workover keywords ......................................................................................426 Figure 138: Structure of the SCHEDULE section in prediction mode ...............................................................432 Figure 139: The WCONPROD keyword ............................................................................................................436 Figure 140: Example of the effect of WCONPROD...........................................................................................438 Figure 141: Application of economic limits........................................................................................................440 Figure 142: Actions taken on violating economic limits.....................................................................................441 Figure 143: A selection of automatic workover keywords..................................................................................442 Figure 144: The WECON keyword ....................................................................................................................443 Figure 145: The CECON keyword......................................................................................................................444 Figure 146: Plugback using WPLUG..................................................................................................................445 Figure 147: The WLIFT keyword for retubing wells..........................................................................................446 Figure 148: The WTEST keyword for well testing.............................................................................................447 Figure 149: The WCUTBACK keyword ............................................................................................................448 Figure 150: Controlling production for a group of wells ....................................................................................450 Figure 151: The GRUPTREE keyword ..............................................................................................................452 Figure 152: The GCONPROD keyword .............................................................................................................454 Figure 153: The GCONINJE keyword................................................................................................................458 Figure 154: Priority control keywords ................................................................................................................462 Figure 155: The GECON keyword .....................................................................................................................464 Figure 156: A typical convergence problem report.............................................................................................468 Figure 157: Typical causes of convergence problems ........................................................................................469 Figure 158: Single Well Coning Model..............................................................................................................475 Figure 159: Model dimensions............................................................................................................................479 Figure 160: Basic model layer data.....................................................................................................................481 Figure 161: XZ model section at Y=0.................................................................................................................483 Figure 162: YZ model section at X=0.................................................................................................................484 Figure 163: Sector Model PROPS Section Construction....................................................................................485 Figure 164: Sector Model Initialisation ..............................................................................................................487 Figure 165: Sector Model History Matching ......................................................................................................491 Figure 166: Sector Model Recovery Optimisation..............................................................................................495
- 11. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 11 of 499 08/04/99 LIST OF EXERCISES Exercise 1: Single Well Coning Model...............................................................................................................475 Exercise 2: Sector Model RUNSPEC Section ....................................................................................................479 Exercise 3: Sector Model GRID Section.............................................................................................................481 Exercise 4: Sector Model PROPS and REGIONS Sections................................................................................485 Exercise 5: Sector Model Initialisation...............................................................................................................487 Exercise 6: Sector Model History Match ............................................................................................................491 Exercise 7: Sector Model Recovery Optimisation ..............................................................................................495
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- 14. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 14 of 499 08/04/99 Purpose Figure 1: ECLIPSE User Course Structure The ECLIPSE 100 USER COURSE is intended to acquaint delegates with the construction of simulation models using the features that are common to all installations of ECLIPSE. As such it takes the structure of a guided tour of the input data and incorporates discussion of the most common ECLIPSE keywords and facilities. ECLIPSE contains a number of additional features that are discussed in advanced user courses, which supplement this course. Also, this course does not specifically address the methodology of reservoir simulation, engineering data preparation and analysis or conduct of simulation studies. For information on GEOQUEST courses on these and other aspects of reservoir simulation and engineering, please approach your course trainer or contact your local Training Administrator. Build and execute simulation models using basic Eclipse facilities Introduction to simulation and the Eclipse software family File naming conventions and structure Data file syntax Principal Eclipse keywords History matching Prediction Discuss one section of the data file at a time Build a model from scratch Eclipse 100 User Course
- 15. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 15 of 499 08/04/99 Purpose During this course you will become acquainted with the basic features and keywords of the ECLIPSE black oil simulator. An overview of the input data and file handling characteristics is followed by lectures on each section of the input data. Each is followed by a practical exercise. Taken together the exercises consist of construction of a simulation model from scratch followed by matching the simulated past production to the measured production, and future recovery optimisation by simulation of a number of production scenarios. The course incorporates tuition in the use of the GRAF post- processor as an integral part and the relationship between ECLIPSE and the other pre- and post-processors in the GEOQUEST Simulation Software suite is also explained.
- 16. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 16 of 499 08/04/99 What is Reservoir Simulation Figure 2: Material Balance Applied to Reservoir Simulation • The simplest simulation is a material balance model • Material balance models use averaged quantities and ignore spatial variation and anisotropy • The reservoir simulator is discrete, finite difference, representation of a continuous system • It takes into account the variation of fluid and rock properties in space i.e. space discretisation. • The simulator advances temporally in discrete steps and can be interrogated at any time i.e. time discretisation. • It is a good reservoir engineering tool, but requires good engineering judgement • It can be used to solve problems that cannot be solved in any other way because it is numerical, not analytical. Mass in - Mass out = Accumulation or Flow in - Flow out = Rate of accumulation Material Balance Model Reservoir Simulation Model
- 17. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 17 of 499 08/04/99 What is Reservoir Simulation Reservoir Simulation, like material balance calculation, is a form of numerical modelling which is used to quantify and interpret physical phenomena with the ability to extend these to project future performance. Material balance has the limiting characteristics of: • No account of spatial variation (so-called “zero-dimensional”) • Reservoir and fluid properties as well as fluid flows are averaged over the entire reservoir • To examine the system at a number of discrete points in time requires a material balance calculation over each time interval. Reservoir simulation, on the other hand, divides the reservoir into a number of discrete units in three dimensions and models the progression of reservoir and fluid properties through space and time in a series of discrete steps. As in material balance, the total mass of the system is conserved. It can be thought of as equivalent to a coupled system of material balance models. This can provide the engineer with far more insight into recovery mechanisms. History matching may even make the engineer aware of missing information. Ultimately, a simulator is only a tool and needs good engineering judgement in order to obtain useful results.
- 18. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 18 of 499 08/04/99 How Does the Model Relate to the Reservoir Figure 3: Reservoir Description versus Simulation Model • The model is not identical to the reservoir • Model performance depends on data quality and quantity • The model reflects the reservoir behaviour if the reservoir is accurately represented • Some phenomena may be unknown or have to be approximated • Data must be validated, i.e. history matched. • Data modifications must be physically viable and justified • The model contains artefacts which are functions of the model construction
- 19. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 19 of 499 08/04/99 How Does the Model Relate to the Reservoir The reservoir and its simulation differ because of the following factors: • Input data is uncertain. A measurement of any kind has an associated uncertainty. For instance, permeability estimates based on core flooding will yield a range of values centred on an average. Deciding whether the available measurements are adequate to calculate an average permeability, and which of the measurements really do represent the permeability the engineer requires is an essential task. One of the largest parts of a simulation study consists of gathering the available data and judging the reliability and relevance of every part of it. This is often much more time consuming than constructing a simulation model. If the model is to behave in the same way as the reservoir, then the input data must accurately represent the reservoir characteristics it is intended to describe although the simulation model does not necessarily bear a superficial resemblance to the reservoir, as in Figure 3. • Reservoir processes and characteristics may be unknown. Well data provides information within the well drainage region plus some general information on the reservoir characteristics beyond that region. Seismic data provides additional structural detail. Beyond this geological information is either inferred or extrapolated. The left hand diagram of Figure 3, for instance, is a highly detailed interpretation but the presence and locations of the various channel sands could only be confirmed by drilling. • The simulation software may be unsuited to modelling certain processes. Simulation models are all discrete numerical approximations to continuous systems. The diffusivity equation on which simulation is based is a non-linear partial differential equation which simulators can only solve directly for the very simplest of models. Instead, approximations in the form of linear difference equations are solved. For instance, the difference equations do not apply to highly compressible fluids and so are unsuited to modelling the detailed dynamics of free gas flow at intermediate to high pressures, typically from approximately 3500 psia. This is usually only relevant for flow into wells from the grid cells they are connected to, in which case a choice of inflow equations is provided. • The simulation model introduces artefacts that alter the model performance. All simulators model the reservoir and wells as a collection of points acting as sources, sinks and receptacles of fluids. These points represent large and complex objects, so
- 20. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 20 of 499 08/04/99 the way in which reservoir properties are averaged to create the properties at discrete points is bound to alter the model performance. For instance, a single simulation grid cell may be at a depth of 3Km, 100m * 100m * 10m, have a single value of porosity, three permeabilities in X, Y and Z, a net-to-gross plus a set of relative permeability and capillary pressure curves. This cell is treated as a single point by the simulator. Fluid will only flow through that cell in the simulation in the same way as in the reservoir rock if all the above properties have been averaged and/or scaled up such that the flow characteristics are preserved. The procedure for doing this is known as upscaling and is essentially a means of countering errors introduced by discretising the reservoir.
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- 22. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 22 of 499 08/04/99 Why Reservoir Simulation? Figure 4: Role of Simulation • It can be used to quickly and cheaply assess various production scenarios • It can accurately model real geological structure and petrophysics • It can model a wide range of recovery techniques • Recognised by banks and funding organisations as supporting evidence for investment decisions • In many parts of the world, it is a statutory requirement Reservoir Simulation Quick and cheap assessment of production scenarios Wide range of recovery techniques Required by law in many countries Recognised by banks and funding bodies Accurate geology and petrophysics
- 23. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 23 of 499 08/04/99 Why Reservoir Simulation? Typical uses of Reservoir simulation include • Accurate determination of recoverable reserves • Prediction of production profiles • Determination of the number of wells needed • Determination of the best perforation policy • Determination of the best well pattern • Assessment of the effects of early gas or water breakthrough and investigation of how to minimise them • Estimation of the size of separation facilities and when they may be needed • Determination of optimum injection rates and the best time for injection • Confirm understanding of reservoir flow barriers to assess whether undrained regions exist • Estimate storage capacities and production rates from underground gas storage facilities • Estimation of optimal means of meeting gas deliverability contracts • Estimation of financial risk by economic analysis of best, worst and most likely scenarios.
- 24. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 24 of 499 08/04/99 Why ECLIPSE? Figure 5: Role of ECLIPSE • Used by almost all oil companies and many government agencies. In certain parts of the world, it has to be ECLIPSE. Over 300 installations worldwide. • Tested and proven to be robust and reliable since it was launch at SPE San Francisco 1983. Supported on many platforms • Extensive features modelling almost every development scenario plus specialised add-on features (ECLIPSE 200). • Nany ancillary packages to facilitate data preparation and processing of results: VFPI, PSEUDO, and GRAF. Additionally, there are GRID, SCAL, SCHEDULE, PVTI, and RTVIEW. There are support teams in many parts of the world to provide user help. • There is a dedicated team of developers working on ECLIPSE. Development continues on the basis of industrial need. Eclipse The "standard" black oil simulator Can model almost any reservoir situation Reliable, accurate, easy to use Integrated with geological and mapping packages Extensive support services Strong product development
- 25. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 25 of 499 08/04/99 Why ECLIPSE? ECLIPSE originated from ECL in the late 1970’s. At the time ECL specialised in seismic data acquisition and quality control, and it became apparent that diversification into dynamic flow modelling would be advantageous. Although a number of reservoir simulators were available at the time, the most popular commercial simulators were not fully implicit and did not use fully implicit well models. The team of reservoir engineers and software developers chosen by ECL was particularly well placed to create a new product having these features, since most of them were very well versed with the PORES simulator. The first commercial release of the new simulator, ECLIPSE, was announced in 1983 SPE. ECLIPSE rapidly became the simulator of choice in Europe and still is today, although the ownership of the technology has changed a number of times since the first release. At present there are in excess of 300 installations worldwide.
- 26. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 26 of 499 08/04/99 ECLIPSE Features Figure 6: ECLIPSE 100 and 200 Features • The basic features are known as ECLIPSE 100 • ECLIPSE 100 features are available on all ECLIPSE installations • Additional features are collectively known as ECLIPSE 200 • ECLIPSE 200 features are part of the ECLIPSE program • ECLIPSE 200 features are activated by special passwords. No re-installation is needed to acquire extra ECLIPSE 200 features. • ECLIPSE 100 and ECLIPSE 200 are usually referred to collectively as ECLIPSE. Basic Features ("Eclipse 100") Free format input 1, 2 or 3-phase simulation Directional Kr Endpoint Scaling CP / BC Geometry Non-Neighbour Connections Analytical and Numeric Aquifers Dual Porosity, Dual Permeability Pc & Kr Hysteresis Vertical Equilibrium Mobile Fluid Correction Fine Grid Equilibration Molecular Diffusion API & Tracer Tracking Vertical, Horizontal & Deviated Wells Crossflow & Commingling in Wells Extensive Surface Facility Modelling Automatic Drill Queue & Workover IMPES & Implicit Formulations Extensions ("Eclipse 200") Local Grid Refinement & Coarsening Wellbore Friction Multi-Segment Wells Flux Boundary Option Surface Networks Gas Lift Optimisation Gas Field Operations Polymer Flood Environmental Tracers Solvent Model Polymer Injection Foam Injection Reservoir Coupling Coal Bed Methane Option Parallel LGRs Shared Memory Parallel Option GI Pseudo-Compositional Model
- 27. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 27 of 499 08/04/99 ECLIPSE Features The basic ECLIPSE options available in all installations are often known as ECLIPSE 100 Additional features purchased separately are known as ECLIPSE 200 ECLIPSE 100 is a fully implicit, three-phase, three-dimensional, general-purpose black oil simulator. Included in the ECLIPSE 100 package are a number of pre- and post-processing and help utilities: • GRAF 2D graphics display package • EDIT syntax sensitive editor specially designed for ECLIPSE data preparation • PSEUDO 3D pseudo function generator • VFPI well bore hydraulics pre-processor • FILL corner point geometry pre-processor • Online help in FrameMaker® format There are also a large number of optional extensions to ECLIPSE 100 to model special reservoir situations. These are collectively known as ECLIPSE 200. All and more of the features listed in Figure 6 are contained in one program but only the basic features are available to all users. The additional features are purchased separately and activated together with the basic facilities by special passwords issued by GEOQUEST. No reinstallation of ECLIPSE is necessary to activate additional features. The software is supported on most computers with an ANSI standard FORTRAN77 compiler and a minimum of 8MB memory, including UNIX workstations (e.g. IBM RS6000, Sun SPARC station and Silicon Graphics), mainframes (e.g. Convex and Cray) and PCs (386 and Pentium).
- 28. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 28 of 499 08/04/99 How ECLIPSE Works Figure 7: Principal Simulator Activities Static Reservoir Description • Construct a geometrical model of the reservoir in discrete grid blocks or cells • For each grid block, supply dimensions, elevation, porosity, permeability PVT and Rock data • Supply fluid formation volume factors, viscosities, densities, gas-oil/oil-gas ratios, rock and water compressibilities • Supply phase relative permeabilities, interface capillary pressures. Initialisation data • Provide fluid contacts, reference depth and pressure and capillary pressures Well data • Provide well and completion locations, Production/injection rates of wells and groups and other data such as skin factors, well radius, well controls, etc. GRID, EDIT Sections Calculate Pore Volumes, Transmissibilities, Depths and NNCs. PROPS, REGIONS, SOLUTION Sections Initialise, calculate initial saturations, pressures and fluids in place Kr Sw FVF,µ P SCHEDULE Section Define wells and surface facilities. Advance through time by material balance for each cell with wells as sinks or sources FlowRate Time OWC GOC
- 29. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 29 of 499 08/04/99 How ECLIPSE Works • ECLIPSE is a batch program. The engineer creates a single input data file for ECLIPSE. This data file contains a complete description of the model. The model consists of reservoir description, fluid and rock property description, initial conditions, wells and their phase flow rates and surface facilities. The input file is a text file containing a collection of keywords and comments. Each keyword has a specific syntax although many keywords have similar or identical syntax. The data file is divided into sections by a few specific keywords. Each section has a particular purpose. In general, ECLIPSE keywords are usable only in certain sections of the data file. ECLIPSE is invoked and the simulation is performed with minimal interaction from the user. • ECLIPSE reads the input data file section by section and processes each section in turn once that section has been read. Various data and consistency checks are made before proceeding to the next section. The last section is exceptional because it specifies time-dependent data and is not read and processed as a whole; the keywords are processed in the order they are read from the data file. • The first task performed by ECLIPSE is to allocate memory for the input data. Although ECLIPSE is dynamically dimensioned and reserves as much memory as required for the simulation as a whole, different kinds of information in the simulation require varying amounts of memory. • The simulation grid geometry and properties are processed into a form more convenient for calculation of flows. For each cell, ECLIPSE calculates the pore volume, transmissibility in three dimensions and cell centre depth and creates connections to other cells to/from which fluids may flow. These quantities may be modified either by the user or by ECLIPSE. • The rock and fluid properties are specified next. The term fluid properties refers to a set of input tables that effectively define the phase behaviour of for each flowing phase. The term rock properties refers to sets of input tables of relative permeability and capillary pressure versus saturation. Effectively, this defines the connate (or irreducible) , critical and maximum saturation of each phase, supplies information for defining the transition zone and defines the conditions of flow of phases relative to one another. This strongly affects the ratios of produced phases, i.e. water cuts and GORs.
- 30. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 30 of 499 08/04/99 • Next, the initial conditions are defined, often by specifying the OWC and/or GOC depths and the pressure at a known depth. ECLIPSE uses this information in conjunction with much of the information from previous stages to calculate the initial hydrostatic pressure gradients in each zone of the reservoir and allocate the initial saturation of each phase in every grid cell prior to production and injection. This is called initialisation. • The final section of the data file is where simulation actually begins. Wells are drilled, perforated and completed, production and injection targets are set up, wells are opened and fluids flow through the reservoir, driven by the wells. • ECLIPSE outputs various information on the simulation results and its progress at dates during the simulation, defined by the user. Once the run has finished, the output is examined using text editors and post-processors of various degrees of sophistication.
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- 32. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 32 of 499 08/04/99 Static Reservoir Description Figure 8: Simulation Grid Data Requirements • Select model geometry • Design areal grid • Design layering structure • Define cell properties • Define region properties
- 33. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 33 of 499 08/04/99 Static Reservoir Description The type of model geometry depends on a number of factors including: • Extent of the area to be modelled • Level of detail required in the study • Level of detail of available data • Complexity of faulting structure • Formation contiguity across faults • Presence of sloping and/or listric (slump) faults • Time available for model construction Available geometrical options are block-centred and corner point. Each may be radial or Cartesian. The essential features are: • Block-centred geometry uses cells with vertical sides, horizontal upper and lower surfaces. The cells are parallelepipeds i.e. each cell has a single height, width, depth and elevation. • Corner point geometry defines cells by the locations of their corners. Corner point cells may be skewed, tilted, wedge-shaped or pinched-out altogether. A model must be either corner point or block-centred. The two cannot be mixed. A model must be either radial or Cartesian but it may contain Local Grid Refinements (LGRs) of different geometry. Having chosen the character of the geometry, the first stage of simulation grid design is usually to create an areal grid. The features of the areal grid are usually • Based on the top structure map • Contains only one layer • Wells are at the centres of grid cells where possible • Faults are at the edges of grid cells where possible • No-flow boundaries are observed • Size and shape of cells varies:- • Cells are often distorted to honour fault traces • Cells are often smaller in the vicinity of wells • Cells may be larger in the aquifer The design of the vertical layering usually follows. This depends on:
- 34. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 34 of 499 08/04/99 • Available horizon data • How members and/or formations are combined into simulation grid layers • The permeability variation with depth • The extent and effectiveness of barriers to vertical communication such as shales Once the geometry is in place the cell properties have to be defined. This includes, but is not restricted to, porosity, permeability in three dimensions and net to gross. This may originate from various sources such as: • Measured values at wells extrapolated over the entire field • Correlations to known quantities • Analogy with neighbouring fields • Geostatistical property modelling After that stage the reservoir is usually subdivided into distinct regions for various purposes such as: • Reporting flows and fluids in place e.g. for formations separated by shales • Specifying regions of distinct fluid contacts e.g. in isolated fault blocks • Specifying regions in which fluids have different PVT properties e.g. oils of different API. • Specifying regions in which rock properties are distinct e.g. connate or irreducible water saturation.
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- 36. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 36 of 499 08/04/99 PVT and Rock Data Figure 9: PVT and Rock Data Requirements PVT Data • Derived from PVT analyses and supplied as tables of properties versus pressure • Phase Formation volume factors Bo, Bg, Bw as appropriate • Phase viscosities µo, µg, µw as appropriate • Gas-oil Ratio Rs and / or Oil-Gas Ratio Rv • The PVT data can vary across the reservoir • Needed to set initial pressure gradients and component distributions Rock Data • Derived from SCAL analysis, supplied as tables of properties versus saturation. • There can be several different curves for various sections of the reservoir • Needed to set maximum, minimum and critical phase saturation in each zone • Required to define and define transition zone saturations
- 37. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 37 of 499 08/04/99 PVT and Rock Data PVT data are the results of laboratory analysis of reservoir fluids. This data is required to: - • Describe the phase behaviour of reservoir fluids at all times • Calculate the density of each phase, which is in turn used • to set up the initial conditions of the simulation • calculate the mass of each phase in each grid block for material balance purposes The fluid PVT properties can vary with depth and/or areally as well as being different in distinct regions of the reservoir. Rock data are the results of special core analysis experiments. This data is required to: - • Set the maximum and minimum saturations of each flowing phase, which in turn is used to define equilibrium phase saturations • Define the transition zone extent and properties • Describe the flow behaviour of distinct fluids in order that phase flows between grid blocks can be calculated.
- 38. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 38 of 499 08/04/99 Initialisation Data Figure 10: Initialisation Data Requirements • Where equilibration is used the initial saturation distribution and pressure at a datum depth are derived from well testing, well logs, RFT and PLT measurements • Where enumeration is used the initial conditions are derived from maps or other distributions of pressure and saturation. • There may be several different equilibration regions Pressure Depth GOC OWC Free Water Level Datum
- 39. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 39 of 499 08/04/99 Initialisation Data Initialisation refers to defining the initial conditions of the simulation i.e. the pressures and phase saturation at the start date of the simulation. The run can start after the onset of production and injection because ECLIPSE has facilities for continuing a simulation from any reporting step of a previous simulation. This is known as a restart run. The initial conditions can be defined in one of three ways. Equilibration Equilibration is the procedure of defining the initial saturation of each phase and initial hydrostatic pressure gradients everywhere based on contact depths and the pressure at a known depth. ECLIPSE assumes that the pressures and saturation are in equilibrium. For this reason, equilibration is appropriate for initialising a simulation prior to production and injection. It is not suitable for defining the initial conditions after production or injection has begun. Enumeration Enumeration is the procedure of explicitly specifying the initial saturation and pressure in each cell. If the model is initialised by enumeration before production and injection, the engineer must take great care to ensure that the pressures and saturation are consistent. Enumeration is appropriate in cases where the water saturation, capillary pressure and pressure distributions are known to a high degree of accuracy throughout the reservoir at a certain time. Unless this is true, the pressures and saturations will be inconsistent and the model will not be stable. In principle, a model may be initialised by enumeration at any stage of the reservoir life. In practice, enumeration is not used to initialise models during production because ECLIPSE has other facilities to do this. Restart Runs A restart run is a means of initialising a simulation based on the intermediate or final results of a previous simulation. ECLIPSE can be instructed to output a comprehensive description of the model at any time during the run, which includes pressure, phase saturations and solution ratios. This output is in a format that ECLIPSE can also read and use to define the initial conditions for another simulation. The method is similar to enumeration inasmuch as the pressures and saturation for each cell are supplied. Restarts are appropriate for running multiple realisations and for production prediction
- 40. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 40 of 499 08/04/99 after history matching has been completed. Restarts are not suitable for defining the conditions prior to injection or production.
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- 42. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 42 of 499 08/04/99 Well Data Figure 11: Well flow rates and monthly averages as viewed using Schedule • Historical production and injection well locations and rates • Locations and rate constraints on new wells and infill wells • Rate constraints on groups of wells • Workovers e.g. plug-backs, stimulation • Drilling queues • Ranking of wells (e.g. by inverse GOR) to meet production targets • Testing shut-in wells
- 43. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 43 of 499 08/04/99 Well Data Well data is presented in two different forms depending on whether the simulation is a history match or a prediction. In history matching the engineer supplies measured phase production rates on a well by well basis and infers reservoir characteristics. In prediction the reservoir characteristics are taken as the best available and the engineer optimises the production subject to economic and facilities constraints. In history matching the wellhead locations are specified as well as completion data and measured phase injection and production rates. The rates may change quite frequently, typically monthly. A number of workovers are also bound to take place. So the simulation might advance for some time until a rate change or workover is specified, after which it advances once again. In prediction typically the wellhead locations and completions are specified together with the wellbore fluid flow correlations in tabular form (VFP tables) and surface facilities and the constraints they impose. Economic limits and operating constraints are specified and the simulation is run for extended periods. ECLIPSE calculates phase production rates subject to the set constraints and performs automatic workovers as required.
- 44. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 44 of 499 08/04/99 Reservoir Simulation with ECLIPSE Figure 12: Simplified Stages of a Full Field Simulation Study • Decide the objective e.g.: optimise well pattern; optimise perforation interval • Select an area of interest • Collect and review data. Select a manageable amount of important data • Build the model i.e. provide data listed in previous pages • Match fluid in place with geological / geophysical estimates • Validate model by history matching if old reservoir. Sensitivity analysis is essential. • Do prediction runs for various production scenarios • Assess multiple scenarios for sensitivity Practical Steps Caution! Decide a clear objective Keep the model simple Select the area of interest Keep the model simple Collect and review data Keep the model simple Build the model Assumptions must be defendable and physically valid Construct small-scale models (e.g. 2D, single well) to understand reservoir processes Match fluid in place Conduct Sensitivity Validate model Make prediction runs
- 45. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 45 of 499 08/04/99 Reservoir Simulation with ECLIPSE Simulation studies are all unique and each demands a unique approach. Nevertheless, they share a common methodology and a number of practical steps. These may be: • Defining a study objective • Choosing an area of interest • Assembling the available data • Establishing the accuracy and relevance of the data • Choosing the most significant information • Reducing the amount of data to make it manageable • Designing and building a coarse model for average pressure and STOIP estimation • Building areal and / or cross-section models to estimate sweep efficiencies and recovery mechanisms, as well as designing pseudofunctions • Building single well models to match individual wells • Amalgamating wells to make “super-wells” or “pseudo-wells” if their number is unmanageable • Reconciling the STOIP with estimates from other sources • History matching a coarse full field model • History matching the full field model sector by sector • Combining the matched sector models • Running a base case prediction • Running multiple predictions to optimise production • Documenting every stage of the process • Removing redundant aspects of the model where possible ECLIPSE and related software are tools designed to assist engineers in fulfilling these and related aims. As such they are an aid to, not a substitute for engineering judgement, and should not be thought of as a black box.
- 46. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 46 of 499 08/04/99 How to Use the Manuals Figure 13: How to use the ECLIPSE documentation • Check the manual and software are of the same version • Check for changes since previous versions • Examine the overview section to find the main ECLIPSE section keywords • Read the overview of each section to know the main rules for data input. Note that some keywords may be required to come before others • Examine keyword summaries to determine which keywords are needed for your specific problem • Refer to the keyword section and technical appendices for more information regarding options and keyword details Eclipse 100 Technical Appendices Eclipse 100 Reference Manual New Developments Introduction Data File Overview Alphabetical keyword list Index Technical descriptions by topic Example data sets Development history
- 47. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 47 of 499 08/04/99 How to Use the Manuals The manuals and the software complement each other, and this course is intended to acquaint the user with both. THE ECLIPSE 100 REFERENCE MANUAL contains • Descriptions of new facilities in the relevant version of the software • An overview of the major ECLIPSE 100 features and characteristics • A brief description of the data file and its structure • A description of every ECLIPSE 100 keyword in alphabetical order, with some specific exceptions that are described in earlier sections. The manual is designed to help users find out the exact effect of a known keyword. THE ECLIPSE 100 TECHNICAL DESCRIPTION contains descriptions of ECLIPSE 100 facilities in alphabetical order. The topics are not easy to classify because they range from system-related matters such as dynamic memory allocation to well design related topics such as inflow performance. All of the information in the manuals is also available online as part of the help facility provided with the Unix installation of the software.
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- 49. FILE ORGANISATION ANDSTRUCTURE
- 50. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 50 of 499 08/04/99 ECLIPSE Input / Output Structure Figure 14: Relationship of Eclipse and pre-and post-processors • Arrows indicate files may be transferred directly between applications • ECLIPSE and related software do not rely on databases for data storage • The Unix or Windows file system is used as the data store • Some applications can be used as pre- and post-processors (two-headed arrows) • The list is not exhaustive • Some combinations of the applications are provided as a suite PVTi PSEUDO SCAL Text Editor FloViz GRID GRAF FloGrid SCHEDULE VFPi Eclipse
- 51. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 51 of 499 08/04/99 ECLIPSE Input / Output Structure There is no underlying database acting as a data repository for input and output data for ECLIPSE and related pre- and post-processors. Instead, files are written to and from the file system on which the applications reside. In general, the applications read and write data only in the directory in which they are running. The main exception is the use of the INCLUDE keyword in ECLIPSE. This is used to bring data from other files containing ECLIPSE keywords into the ECLIPSE data file. For instance INCLUDE GRID.GRDECL / Will read a file named GRID.GRDECL from the current directory into the ECLIPSE data file. INCLUDE ‘../../welldata/97match/sect2.sched’ / will read the file indicated by the relative pathname. Absolute pathnames are also allowed. Also, files GRID.GRDECL and sect2.sched may themselves contain INCLUDE keywords. Data is transferred between applications by outputting files from one and reading the files into another, with a few exceptions. This is not the case in general with GEOQUEST software, the majority of which extract information from underlying databases. Note that by no means all the GEOQUEST applications are shown in Figure 14
- 52. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 52 of 499 08/04/99 ECLIPSE Output Files Figure 15: Eclipse outputs • The ECLIPSE input data file has a suffix .DATA (Unix) or .DAT (PC). • Screen output or short output • Print file • Debug file • Summary files • Run summary file • Summary specification file • Grid file • Init file • Restart file or files • Flux, RFT and /or Save files Eclipse SAVE File FLUX File RFT File Short Output Main Output Debug Output Grid File Init File Spec File Summary File Restart File RSM File Printer Other Programs At each report step GRAF
- 53. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 53 of 499 08/04/99 ECLIPSE Output Files Short output Short output or screen output is a means of tracking the run in progress and is usually displayed on the monitor. It includes • A number of average quantities such as field GOR, OGR, WCT and pressure • Comments, Messages, Warnings, Problems and Bugs. These range from informative output to notification of failure to proceed. • Information on workovers and shut-ins at well, group and field level plus changes of control mode. • Notification of output of output of results. Short output is displayed if ECLIPSE is run in the foreground. If run in the background a .LOG file is generated instead. Main output Main output is written to the .PRT file. It contains all of the short output plus additional information, if requested. The .PRT file is created whether ECLIPSE runs in the foreground or the background and is always a readable text file If ECLIPSE runs in the background (as a batch process), the .LOG file in general contains all that is in the .PRT file (although the user can alter this) as well as the details of the batch process itself. Debug Output The .DBG file contains debug output. A debug file is created by default and contains a limited amount of information. Debug information is in coded form, may be quite voluminous and is used in general by software developers and support staff. Users are recommended not to adjust the default debug output options as a matter of course. Summary file or files Summary output is generated at a number of reporting times during the simulation and is used to generate line plots. The line plots are often quantities that vary with time, such as field oil production, well water cut, group injection rates and other data. The data is usually load into GRAF and may also be used to generate crossplots.
- 54. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 54 of 499 08/04/99 Summary Spec File The summary specification file is used by a number of applications, although the user need never refer to it. It contains a listing and description of the contents of the summary files Run Summary File The run summary file contains the same information as the summary files, only in tabular form. Run summaries can be imported into spreadsheets relatively easily. Restart Files Restart files contain a complete description of the reservoir at the stage they were written. This includes pressure, phase saturation and Rs and/or Rv for each cell as appropriate plus a complete description of the wells and surface facilities as well as the rate information throughout. A notable exception is VFP tables, which are not written to restart files. Restart files are commonly used to create graphical displays of the model in section and in three dimensions. ECLIPSE can be instructed to output restart data for graphical use only; these occupy less disk space than the default restart files. Grid File Contains only the simulation grid geometry Init File The initial file contains information on the static reservoir description • Cell dimensions, top depths and centre depths • Cell properties such as porosity, permeabilities, pore volume and transmissibility. • PVT and saturation function tables. • The distribution of reservoir regions within the model Flux files Flux files contain the flows and pressures at the boundaries of a number of flux regions. RFT Files These contain simulated RFT data, i.e. pressures and saturations versus depth. Save file The save file contains a condensed version of part of the information in the Eclipse input data file. It includes the static reservoir description, rock and fluid properties,
- 55. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 55 of 499 08/04/99 aquifer data and output controls but excludes the wells and surface facilities and the constraints they impose. The save file is used in restart runs. Error files The error file contains system information in the event of failure of a simulation. It is a report created by the Unix file system on the activities of the simulation process.
- 56. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 56 of 499 08/04/99 ECLIPSE Output Styles Figure 16: Available Eclipse output types • The output style is set in the RUNSPEC section • Any combination of formatted/unformatted and unified/multiple may be used • The default is unformatted, multiple Formatted Unformatted Unwanted files may be deleted Files are relatively small files are not portable Last file lost on crash Limited to 9999 reports One file Unlimited number of reports Last report lost on crash One file Unlimited number of reports Readable Easily transferred between platforms Relatively large in size Last report lost on crash Readable Easily transferred between platforms Relatively large in size Last file lost on crash Limited to 9999 reports Unified Multiple
- 57. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 57 of 499 08/04/99 ECLIPSE Output Styles ECLIPSE outputs certain files in a variety of styles as requested by the user. These may be any combination of formatted/unformatted and unified/multiple • A formatted file is ASCII i.e. text • An unformatted file is binary i.e. not man-readable • A unified file is a single file containing output from a number of reporting steps • Multiple files each contain output at a single reporting step. Not all ECLIPSE output is affected by these choices. Files that may be unified or multiple are the restart and summary files. Files that may be formatted or unformatted are all files except the .PRT, .LOG, .RSM and .DBG files; these are always formatted. The choice of output style is made in the RUNSPEC section. The default is unformatted, multiple. The keyword UNIFOUT selects unified output and the keyword FMTOUT selects formatted output. The various styles each have their advantages and disadvantages: Unformatted Such files are small compared to formatted files and can be read and written relatively rapidly. Since they are binary they cannot be read using text editors. Also, they are not necessarily portable between different platforms. Not all computers read binary data from disk in the same way. For example, an unformatted restart file written on a PC may not be read correctly by a Silicon Graphics machine, and vice versa. To ensure portability the files should first be converted to formatted using the @convert utility macro (p.67). Formatted Such files are large (i.e. occupy more disk space) compared to unformatted files but are man-readable. They are portable between platforms since they use the ASCII character set. The benefits of routinely outputting formatted restart and summary files are dubious since the information they contain is in coded form in any case. Multiple Multiple files contain restart or summary output at each report step. Their main advantage is that if the run terminates unexpectedly or the disk space runs out, then only the results from the current reporting step are lost. All previous results are unaffected since the files have already been written and closed. Their main disadvantage is that if a number of simulations with very similar names reside in one directory, keeping track of
- 58. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 58 of 499 08/04/99 then output may become confusing. Also, the number of multiple output files is limited to 9999 i.e. only that many reporting steps can be output. Unified Unified files are single files containing output for each reporting step. A simulation using unified files will typically output a single summary file and a single restart file. Their main advantage is that if a number of simulations reside in one directory, their output is quite tidy. Note that if the run terminates unexpectedly or disk space runs out, the output up to and including the previous report is preserved. There is no limit on the number of reporting steps a unified file contains.
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- 60. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 60 of 499 08/04/99 Output File Names Figure 17: Eclipse filenames for each output style part 1 • Output is to the current directory • Input is from the current directory, except for data read using INCLUDE • Bold underlined names are ECLIPSE defaults • File extensions and case must be set in a separate configuration file • Output style is defined in the ECLIPSE data file EXAMPLE.DBG EXAMPLE.LOG EXAMPLE.PRT EXAMPLE.GRD EXAMPLE.FGR EXAMPLE.INI EXAMPLE.FIN EXAMPLE.SMS EXAMPLE.FSM EXAMPLE.SAV EXAMPLE.FSV EXAMPLE.RSM EXAMPLE.RFT EXAMPLE.FRF EXAMPLE.FLX EXAMPLE.FFX Short Output Debug Output Print File Grid Geometry File Initial File Summary Specification file Save File Run Summary File RFT Output Flux file EXAMPLE.DATA ANSI EXAMPLE.DBG EXAMPLE.LOG EXAMPLE.PRT EXAMPLE.GRID EXAMPLE.FGRID EXAMPLE.INIT EXAMPLE.FINIT EXAMPLE.SMSPEC EXAMPLE.FSMSPEC EXAMPLE.SAVE EXAMPLE.FSAVE EXAMPLE.RSM EXAMPLE.RFT EXAMPLE.FRFT EXAMPLE.FLUX EXAMPLE.FFLUX UNIX
- 61. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 61 of 499 08/04/99 Output File Names In general ECLIPSE is invoked in the current directory and reads and writes data to and from the current directory. The exceptions to this are data files incorporated into the ECLIPSE data file using the INCLUDE keyword (p.50). The input and output file extensions depend on the following settings • Whether Unix (long) or ANSI (3-character) file extensions are in use • Whether the case is upper or lower • Whether output is unified • Whether output is formatted File Extensions and Case The default extensions to the filenames depend on whether the operating system is Unix or PC-based. For instance, the ECLIPSE input data file has the suffix .DATA in Unix and .DAT on a PC non-Windows system. The reason for the difference is that Unix permits file extensions of any length while PC file extensions are traditionally restricted to three characters. With the development of more sophisticated PC operating systems, three- character file extensions have become obsolete and will not be discussed further. The default extensions are set upon installation in a master configuration file named CONFIG.ECL. Refer to p.64 for information on File Locations. Each time ECLIPSE is run this file is copied to the current directory as ECL.CFG, the information in it is used to set a number of application defaults and it is deleted when the simulation terminates. It contains, among other things: • Passwords to activate the software • Default case (upper or lower) • Default file extension (Unix or ANSI) • Temporary file locations • Pointers to fonts to be used • Peripheral device driver settings • The default settings for filenames are • Upper case, long extension on Unix systems • Lower case, short extensions on PC On a Unix system the relevant section of CONFIG.ECL resembles the following:
- 62. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 62 of 499 08/04/99 SECTION SYSTEM CASE UPPER --CASE LOWER --CASE BOTH SUFFIX UNIX --SUFFIX ANSI A double dash denotes a comment. Users should alter the settings in CONFIG.ECL with extreme caution, as this will affect everyone using ECLIPSE and related software. Instead, the settings that need to be modified may be defined in a local configuration file in the current directory named ECL.CFA. ECL.CFA is read after ECL.CFG and any altered settings are used. ECL.CFA is not deleted when the simulation is over. Figure 18: Eclipse filenames for each output style part 2 How to Alter Personal Default File Extensions and Case This may be necessary if, for instance, you have transferred ECLIPSE data from a PC to a Unix platform, or vice versa. This is shown in Figure 19. EXAMPLE.USY EXAMPLE.FUS EXAMPLE.Snn, Tnn, Unn EXAMPLE.Ann, Bnn, Cnn EXAMPLE.Xnn, Ynn, Znn EXAMPLE.Fnn, Gnn, Hnn EXAMPLE.URS EXAMPLE.FUR Multiple Summary Output Unified Summary OUtput Multiple Restart Output Unified Restart Output EXAMPLE.DATA ANSI EXAMPLE.UNSMRY EXAMPLE.FUNSMRY EXAMPLE.Snnnn EXAMPLE.Annnn EXAMPLE.Xnnnn EXAMPLE.Fnnnn EXAMPLE.UNRST EXAMPLE.FUNRST UNIX
- 63. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 63 of 499 08/04/99 Figure 19: Setting Personal File Extensions and Cases This will affect every application in the ECLIPSE suite and related software that is invoked in that directory without affecting users operating in other directories. Output Styles As described on p.56, the file suffix generally reflects the output style. For instance, most formatted files have a suffix beginning with the character F; exceptions are multiple restart and summary files. Figure 17 and Figure 18 show the extensions used in Unix and PC environments, depending on whether unified/multiple and formatted/unformatted output is chosen. Bold underlined filenames are the ECLIPSE defaults. é Go to your working directory é Type @copyconfig (Unix) or $copycfg (PC) to copy CONFIG.ECL to ECL.CFG in the current directory. Alternatively, copy it directly from its location in the directory structure. é Rename ECL.CFG to ECL.CFA é Open ECL.CFA in the text editor of your choice é Remove any lines not relevant to the changes you need to make é Comment out settings you wish to deactivate using a double dash é Activate new settings by either removing double dashes from lines already in the file or by inserting your own. é Save and exit. é For example: SECTION SYSTEM CASE UPPER --CASE LOWER --CASE BOTH SUFFIX UNIX --SUFFIX ANSI
- 64. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 64 of 499 08/04/99 File Locations Figure 20: Eclipse and related software file locations • There is an environment variable $ECLARCH for the location of the software, often /ecl • Programs are invoked from the current directory using macros found in directory $ECLARCH/macros • $ECLARCH/macros contains a license file typically named license.dat • Directory ECLARCH/macros also contains a master configuration file, CONFIG.ECL • CONFIG.ECL is copied to your working directory as ECL.CFG when ECLIPSE is invoked • ECL.CFG regulates file extensions, licensing, device drivers and other functions • Configuration settings in a file ECL.CFA overwrite corresponding settings in ECL.CFG • ECL.CFG is deleted on exiting a program but ECL.CFA is not /ecl /96a /97a /98a /macros /data/source /pseudo /eclipse/grid/e300/rtview/pvti /vfpi/weltest/graf /tools
- 65. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 65 of 499 08/04/99 File Locations The environment variable $ECLARCH contains the directory location of the software. To view this on a Unix machine type echo $ECLARCH On a PC type set in a DOS window. On a Unix machine the location is usually /ecl whereas on a PC it is usually C:ecl. Subdirectories such as 95a, 96a, 96b, 97a contain different versions of the release software. They will not in general each contain complete sets of executables. The macros subdirectory contains: • The master configuration file CONFIG.ECL • The license file, usually named license.dat. • Macros such as @eclipse (Unix) or $eclipse (PC) to run the applications (eclipse.exe) • Utility Macros for performing various data manipulation and system tasks. The tools subdirectory contains the executables relating to the Utility Macros
- 66. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 66 of 499 08/04/99 Utility Macros Figure 21: Eclipse suite utility macros • @convert converts ECLIPSE output files from one style to another • @copyconfig copies CONFIG.ECL to ECL.CFG • @ecl2avs converts ECLIPSE output to FLOVIZ-compatible input • @expand incorporates INCLUDE files into an ECLIPSE data file • @extract extracts a subset of the simulation output • @flexstart restarts the license manager daemon • @frame starts the online help viewer • @lmdown shuts down the license manager daemon • @lmhostid establishes the machine host id for licensing purposes • @lmstat interrogates the license manager for status of software features • All are run from a Unix shell as a command line. Prompts for action are provided. • These are the Unix names. On a PC generally the @ symbol is replaced by $ /ecl /macros @change_prefix @change_suffix @check_args @check_chip @check_motif @check_version @check_xserver @clan @clan100 @colormap @convert @copyconfig @datacheck @datestamp @e300 @e300_q @e500 @ecl2avs @eclipse @eclipse_batch @eclipse_rc @ecljobs @eclproject @eclrc @eclrc.install @edit @expand @extract @fill @flexstart @flogrid @floviz @frame @frame2 @geonet_setup @get_lsf_queues @gradient @graf @grid @grid_receive @gs @ipcfree @lmdiag @lmdown @lmhostid @lmreread @lmstat @lower @merge @office @pldebug @plot_zeh @plot_zeh_save @plot_zeh_small @postp @preview
- 67. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 67 of 499 08/04/99 Utility Macros @convert The @convert macro is used to create duplicate ECLIPSE output in a different style. For instance, formatted ECLIPSE output could be converted to unformatted. Since the file extensions for each output style are different, the original data is not affected. @copyconfig This macro copies the CONFIG.ECL file to the current directory as ECL.CFG. This is normally done by any macro that invokes ECLIPSE and related software (such as @eclipse, @grid). Occasionally CONFIG.ECL must be copied using @copyconfig in situations where, for instance, the permissions in the current directory would not permit the user to write the ECL.CFG file. On a PC this is named $copycfg. @ecl2avs This is used to convert ECLIPSE output to a format that is suitable for FLOVIZ and RTVIEW. It is not available on PC installations. @expand Many data files incorporate data from other files using the INCLUDE keyword. For instance, grid geometry data is often voluminous and located in a directory separate from the ECLIPSE input file. The @expand macro will place the grid geometry data into a copy of the ECLIPSE input file. This ensures that if a dataset has to be transferred all of the associated data will also be transferred. @extract Large and complex simulation models can produce too much output for the GRAF post- processor to load. @extract provides means of selecting parts of the output over a specified period. This includes the summary, restart, grid and initial file output. For instance, it may be desirable to load only one sector of a full field for the first few years of simulation. @flexstart Starts the flexlm license manager daemon. On a PC this is named $lmup. @frame Run the on-line help application. This is not available on PC installations.
- 68. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 68 of 499 08/04/99 @lmdown Shut down the flexlm license manager daemon @lmhostid Displays the unique id of the computer on which the software is installed. This is used for licensing purposes. On a PC this is named $lmhid. @lmstat Displays the total number of licenses available and the number currently in use for each application of the ECLIPSE suite and related software
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- 70. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 70 of 499 08/04/99 Input Data File Structure Figure 22: Major sections of the Eclipse input data file • Each section is marked by a major section keyword • Major section keywords close the previous section • Sections must be presented in the order shown • Some sections are optional • Most keywords are specific to one section RUNSPEC COMPULSORY --GENERAL MODEL CHARACT ERIST ICS GRID COMPULSORY --GRID GEOMET RY AND BASIC ROCK PROPERT IES EDIT OPT IONAL --MODIFICAT ION OF T HE PROCESSED GRID SECT ION PROPS COMPULSORY --DAT A FOR PHASE PVT PROPERT IES IN T ABULAR FORM AND OT HER PVT DAT A --ROCK COMPRESSIBILIT Y, RELAT IVE PERMEABILIT Y & CAPILLARY PRESSURE T ABLES. REGIONS OPT IONAL --SBDIVISION OF T HE RESERVOIR ACCORDING T O COMMON PROPERT IES --AND REPORT ING REGIONS SOLUT ION COMPULSORY --INIT IAL CONDIT IONS ARE SPECFIED HERE SUMMARY OPT IONAL --OUT PUT FOR LINE PLOT S IS REQUEST ED HERE SCHEDULE COMPULSORY --WELLS, COMPLET IONS, RAT E DAT A, FLOW CORRELAT IONS, SURFACE FACILIT IES --AND SIMULAT OR ADVANCE, CONT ROL AND T ERMINAT ION ARE SET HERE
- 71. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 71 of 499 08/04/99 Input Data File Structure The input data file is subdivided into sections according to various tasks that ECLIPSE performs in a specific order. The keywords listed in Figure 22 mark the end of the previous section and the beginning of the next. They take no arguments and must be presented in the order shown, although some are optional. RUNSPEC The RUNPSEC section specifies general model characteristics and is used by ECLIPSE to internally allocate memory to the various components of the simulation. The RUNSPEC section is mandatory, except for fast restarts. GRID The GRID section contains the specification of the static reservoir description, such as the grid geometry data, porosities, permeabilities, net-to-gross and numerical aquifer specification. The GRID section is mandatory, except for fast restarts. EDIT The EDIT section is optional. It is used to modify the grid geometry data once ECLIPSE has processed GRID section data to a form more suitable for use in flow calculations. PROPS The PROPS section contains the fluid PVT properties, relative permeabilities and capillary pressure data. REGIONS The REGIONS section is optional. It is used to group cells together into regions of distinct reservoir characteristics such as rock compressibility or initial oil API. Regions may also be defined for reporting purposes. The REGIONS section is mandatory, except for fast restarts. SOLUTION The SOLUTION section specifies the conditions at the start of the simulation run. It is mandatory, except for fast restarts. SUMMARY The SUMMARY section is optional. It is used to specify the data output for line plots.
- 72. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 72 of 499 08/04/99 SCHEDULE The SCHEDULE section contains all the data on wells, surface facilities, flow correlations and simulation advance and termination. Without a SCHEDULE section, ECLIPSE does not output restart files. To output the initial conditions, a SCHEDULE keyword is required and the simulation must be run for at least one timestep.
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- 74. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 74 of 499 08/04/99 Data File Syntax Figure 23: Summary of data file syntax • The ECLIPSE input data file is a text file • Information is specified using keywords no more than eight characters in length • Anything after the eighth character of a keyword is interpreted as a comment • Keyword arguments should begin on the following line • Keywords begin in column 1 by default • The file is 132 characters wide by default • Anything after the 130th character is interpreted as a comment • Comments elsewhere must begin with a double dash or follow a forward slash (/) • ECLIPSE keywords are not case-sensitive • Hidden text such as tabulation and control characters may interfere with keyword function 123456789012345678901234567890 132 --This comment denotes the beginning of the data file proper | --Keywords must start in the first column read, which is 1 by default | RUNSPEC Can place comments in the 8th column following the keyword | --This is a comment | --followed by another comment | EDIT This section is optional | | PROPS This section is compulsory | DENSITY | --Oil Water Gas | 45 63 0.07 / Comments can be placed after | -- the terminating slash | REGIONS This section is optional | --This is another comment | SOLUTION | columns Eclipse keywords are not case sensitive | --First Last 1 33 / | Anything beyond the final column is a comment SUMMARY | | SCHEDULE | | END |
- 75. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 75 of 499 08/04/99 Data File Syntax The contents of the ECLIPSE input data file is text, with one exception. It is possible to specify grid geometry in binary format (see the GDFILE keyword p.186). Apart from this, only standard ASCII characters should be used in the file. Characters such as the tab character and control character are not acceptable and can cause data to be read incorrectly, leading to errors or convergence problems. Keyword length is limited to eight characters; anything after the eighth character is taken as a comment. For this reason the data following a keyword must begin on the next line. By default the first character of each keyword should be in the first column of the file, although this may be changed using the COLUMNS keyword. The file is taken as 132 characters wide or 132 columns wide. Anything to the right of column 130 is interpreted as a comment. All the applications in the ECLIPSE software suite observe this convention, so the COLUMNS keyword may only be needed if data from third party packages is incorporated into the software. If the first active column is moved to the right, anything to its left is treated as a comment. Comment lines begin with a double dash and may be placed anywhere in the file provided they begin in the first column or begin after the forward slash terminating a keyword or record of a keyword.
- 76. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 76 of 499 08/04/99 Keyword Syntax Figure 24: Syntax of Eclipse keywords • Every keyword has its own syntax • Many keywords share a common syntax • Most keyword arguments have default values as specified in the ECLIPSE 100 REFERENCE MANUAL • Omitting a keyword is equivalent to defaulting all its arguments • Keywords are not case sensitive • Quotes are only needed when an argument contains special characters RUNSPEC Put Only RUNSPEC section keywords here TABDIMS --1 2 3 4 5 6 7 8 --ntsfun ntpvt nssfun nppvt ntfip nrpvt N/A ntendp 3 3 1* 1* 1* 20 1* 1* / TABDIMS --1 2 3 4 5 6 7 8 --ntsfun ntpvt nssfun nppvt ntfip nrpvt N/A ntendp 3 3 3* 20 2* / TABDIMS --1 2 3 4 5 6 7 8 --ntsfun ntpvt nssfun nppvt ntfip nrpvt N/A ntendp 2*3 3* 20 2* / TABDIMS --1 2 3 4 5 6 7 8 --ntsfun ntpvt nssfun nppvt ntfip nrpvt N/A ntendp 2*3 3* 20 / GRID Put only GRID section keywords here PROPS Put only PROPS section keywords here SOLUTION Put only SOLUTION keywords here SCHEDULE Put only SCHEDULE section keywords here WELSPECS --Well Group I J BHP Ref Phase PROD1 Group1 5 5 1* OIL / Quotes are generally not required around strings PROD2 Group1 9 9 1* GAS / ’INJ*’ Group1 1 1 1* WAT/ Quotes are needed when wildcards are used /
- 77. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 77 of 499 08/04/99 Keyword Syntax Although the syntax of each keyword is defined in the ECLIPSE 100 REFERENCE MANUAL, many, but by no means all, keywords have one of two types of syntax. The first is <keyword> <value1> <value2> <value3> ……. <value NX*NY*NZ> / NX*NY*NZ is the total number of cells in the model. This usually applies to quantities that take one value per cell such as porosity, net-to-gross, fluid in place region number. The other common syntax is <keyword> --First data record <value1> <value2> <value3> ……. <value N1> / --Second data record <value1> <value2> <value3> ……. <value N2> / …….. …….. ……….. --final data record <value1> <value2> <value3> ……. <value N> / / Where N1, N2, N may differ. This usually applies to well keywords, such as specifying the completion data for a number of wells (one per record, for instance) using a single keyword. • A single default value is specified as 1* with a space either side. N Multiple adjacent default values can be specified as N*<value>. The four examples of the TABDIMS keyword in Figure 24 are all equivalent. • Omitting a keyword is equivalent to specifying it with default values for every argument. • If the last item of a keyword or record is defaulted, it need not be specified as 1*; the forward slash (/) can be brought forward as in the fourth example of TABDIMS in Figure 24. • There is no need for a space between the final value and the forward slash terminating the record or keyword. • Quotes are in general not needed. Exceptions are where a keyword argument contains special characters. For example
- 78. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 78 of 499 08/04/99 INCLUDE ‘../../model98/schedule/prediction.sched’ / requires quotes whereas INCLUDE prediction.sched / does not.
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- 80. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 80 of 499 08/04/99 Any Section Keywords Figure 25: Keywords for any section • Most keywords can only be used in one section of the data file • Some keywords can be used in several sections • A few can be used anywhere • The ECLIPSE 100 REFERENCE MANUAL describes the sections each keyword may be used in. INCLUDE Incorporate data from other files into the Eclipse data file COLUMNS Set the position of the first and last columns of the data file DEBUG Request debugging information NOECHO Suppress output of keyword contents to the PRT file ECHO Enable output of keyword contents to the PRT file EXTRAPMS Display the last VFP and / or PVT table extrapolation OPTIONS Activate various special program options MESSAGES Set print and stop limits for events of various severities NOWARN Suppress all supplementary PRT file output FORMFEED Set the formfeed character LOAD Access a SAVE file for fast restarts.
- 81. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 81 of 499 08/04/99 Any Section Keywords INCLUDE Incorporates data from external files into the ECLIPSE data file. COLUMNS Set the positions of the left and right columns between which ECLIPSE reads data. Default positions are 1 to 130 inclusive. The upper limit on number of columns is 132. DEBUG Requests debug output to the .DBG file. Users are recommended not to use this. NOECHO Suppresses output of keyword arguments to the PRT file. Only the keywords themselves are written to the PRT file, not the data following them. By default, the arguments are written to the PRT file. ECHO Activates output of keyword arguments to the PRT file following suppression by NOECHO. EXTRAPMS Writes information on the VFP and / or PVT table extrapolation performed by ECLIPSE. OPTIONS Activates special program options within particular ECLIPSE facilities. These are quite specialised and users are generally recommended to omit this keyword altogether. The default behaviour of ECLIPSE, however, may differ between versions. For instance, since version 95a, MINPV has been copied to LGR cells. Previously, MINPV for LGRs was not copied from the global grid to the LGRs. Users requiring pre-95a behaviour in later versions need to invoke it using the OPTIONS keyword. MESSAGES Sets the numbers of messages of varying severity that are output to the PRT file and the stop limit. The run will stop if a particular type of message is generated more times than its stop limit. Once the stop limit has been reached the run switches to data checking mode and no calculations are performed after the next simulation advance keyword is read.
- 82. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 82 of 499 08/04/99 NOWARN Suppresses message generation. Users are strongly recommended not to use this keyword. FORMFEED Sets the form feed character in the print file. This allows the user to specify how ECLIPSE should insert form feeds in the PRT and RSM files. The default is the standard FORTRAN carriage control. LOAD Load a SAVE file to perform a fast restart. The SAVE file contains processed data from the RUNSPEC, GRID, EDIT, PROPS and REGIONS sections of a previous simulation. LOAD is not strictly an any section keyword, but a replacement for a number of other keywords. Those sections should be removed from the restart run.
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- 84. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 84 of 499 08/04/99 Purpose of the RUNSPEC Section Figure 26: Minimum RUNSPEC options • The RUNSPEC section allocates memory for various components of the simulation sequentially within the main memory area • These components include wells, tabular data, the simulation grid and the solver stack • Simulation options are also invoked in the RUNPSEC section e.g. Vertical Equilibrium • RUNSPEC takes the format of keywords followed by optional parameters • Pre-96a versions require fixed format RUNSPEC. These are forward compatible and may be freely converted to the new format • Several keywords must be used to specify a usable minimum; the rest are optional. • Use comments liberally • Figure 26 shows the bare minimum required in the RUNSPEC section • Omitting a keyword is equivalent to specifying a default --BEGINNING OF MINIMUM RUNSPEC SECTION RUNSPEC TITLE THIS IS THE MODEL NAME/ DIMENS --NX NY NZ --THIS IS THE NUMBER OF CELLS IN I, J AND K, IN THAT ORDER E.G. 20 5 10 / FIELD UNITS MAY BE FIELD, METRIC OR LAB OIL PHASES PRESENT MAY BE OIL WATER WATER, GAS, DISGAS, VAPOIL START START DATE OF THE SIMULATION, FOR INSTANCE 1 JAN 1990 /
- 85. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 85 of 499 08/04/99 Purpose of the RUNSPEC Section Installations prior to version 96a included several ECLIPSE executables, each designed to accommodate simulations requiring up to 20, 40, 60 and 80 Mb of RAM. These were typically named eclipse_20Mb.exe, eclipse_40Mb.exe, etc. Larger simulations were catered for by either supplying one-off versions of the code or providing instructions to enable users to alter the dimensioning of ECLIPSE themselves. Since the 96a release ECLIPSE has been dynamically dimensioned and allocates as much RAM as necessary for a simulation. Since then only one executable, eclipse.exe, has been needed. Memory is used sequentially while ECLIPSE reads the input data file. The RUNSPEC section is necessary to specify how the RAM should be subdivided internally to accommodate each component of the simulation (such as wells, PVT tables and grid geometry) as well as to specify the basic character of the model and a start date. The mandatory keywords are specified in Figure 26; some require extra parameters. Tabular input data such as PVT and relative permeability information occupy a relatively small proportion of the memory even when the number of tables and their size is very large. The bulkiest parts of the simulation are the reservoir grid and the solver stack. The grid contains information on the geometry, depth, porosity, permeability, and net-to-gross of each cell. ECLIPSE converts this to an array of pore volumes, transmissibilities and cell centre depths, which are then used internally when calculating flows from cell to cell. Pore volume is a scalar quantity whereas transmissibility is a vector, so the minimum information required to describe the reservoir grid is five numbers per active cell. The total number of cells in the simulation is equal to NX*NY*NZ. At each timestep ECLIPSE solves a set of equations for the pressure, saturation and gas- oil and/or oil-gas ratio in each cell. Solutions at successive simulation iterations must be orthogonal, so ECLIPSE requires rapid access to several previous solutions. This is known as the solver stack and is set to 10 by default but may be altered using the NSTACK keyword. In a dead oil/water simulation ECLIPSE solves for water saturation and pressure, giving two numbers per active cell per timestep or thirty numbers per active cell at any moment in the solver stack by default. Pre-96a versions of ECLIPSE used a fixed format RUNPSEC section; this format has not been updated. Later versions use a free-format RUNPSEC section using keywords as in Figure 26. Although recent versions of ECLIPSE can read the fixed-format RUNPSEC
- 86. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 86 of 499 08/04/99 section, some new facilities have become available in the free-format RUNPSEC which pre-96a versions cannot use. How to Convert Fixed Format RUNPSEC to Free Format Go to the directory containing the data file to be converted • Make a copy of the data file • Type @edit (Unix) or $edit (PC). This is an editing utility originally designed to ease ECLIPSE 100 keyword input. • When prompted for a filename, supply the full name of the copy you have made • When the editor screen appears move the blinking cursor to the line containing the RUNSPEC keyword. Use the arrow keys on the keyboard. • Type CV then type the ESC key twice. When prompted to type send, type the ESC key twice. When you return to the editor screen type X followed by ESC twice. • A new format RUNSPEC section will have been added to the copied file. Delete the old format RUNSPEC section before proceeding.
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- 88. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 88 of 499 08/04/99 RUNSPEC Keywords and Switches Figure 27: Eclipse 100 RUNSPEC keywords in alphabetical order • These are the ECLIPSE 100 keywords for the RUNSPEC section • ECLIPSE 200 options may have extra keywords • Some take arguments, others do not. • A full description can be found in the ECLIPSE 100 REFERENCE MANUAL ACTDIMS LAB START API MEMORY TABDIMS AQUDIMS METRIC TEMP BRINE MISCIBLE TITLE CART NINEPOIN TRACERS DIFFUSE NONNC UNIFIN DIMENS NOPC9 UNIFOUT DISGAS NOSIM VAPOIL DISKING NSTACK VE DUALPERM NUMRES VISCD DUALPORO NUPCOL VFPIDIMS ENDSCALE OIL VFPPDIMS EQLDIMS PIMTDIMS WATER EQLOPTS RADIAL WELLDIMS FAULTDIM REGDIMS FIELD ROCKCOMP FMTIN RPTRUNSP FMTOUT RSSPEC GAS SATOPTS GRAVDR SAVE GRIDOPTS SMRYDIMS
- 89. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 89 of 499 08/04/99 RUNSPEC Keywords and Switches The RUNPSEC section is used to allocate memory and activate program options. The memory allocation keywords require either an upper limit or an exact number. For instance, the number of lines of data in any PVT table (4th item, named NPPVT in TABDIMS) is an upper limit. On the other hand, the number of cells in I, J and K specified in DIMENS must be exact. Other keywords activate specific program options such as endpoint scaling, molecular diffusion calculation or data checking mode. Commonly used RUNSPEC keywords and switches AQUDIMS specifies the number and dimensions of numerical an analytical aquifers DIMENS specifies the model dimensions. This keyword is required. DISGAS, GAS, OIL, VAPOIL, WATER specify phases used in the model. There must be at least one phase. DUALPORO enables the dual porosity option ENDSCALE sets endpoint scaling options EQLOPTS sets a number of options used in defining the initial pressures and saturations FIELD, METRIC or LAB specifies the unit system used. A single unit system is used for all data in the model. FMTIN, FMTOUT specify formatted input and output, respectively. NOSIM turns off simulation in the SCHEDULE section. This is very useful for checking for keyword errors before running the simulation. NSTACK specifies the length of the stack of previous solutions. Difficult problems may require a value greater than the default of 10. Do not set it to greater than the maximum number of linear iterations minus one. NUPCOL defines the number of non-linear iterations per timestep in which well targets are updated. Values larger than the default of 3 may sometimes be required. RADIAL specifies radial model geometry RPTRUNSP produces a listing in the PRT file of the RUNPSEC options and switches used in the simulation. START sets the date of the beginning of simulation. This keyword is required. TABDIMS specifies input PVT and saturation function table dimensions TITLE sets the name of the run. This keyword is required. UNIFIN, UNIFOUT specify unified input and output, respectively. VE indicates that the Vertical Equilibrium option is active.
- 90. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 90 of 499 08/04/99 VFPIDIMS, VFPPDIMS specify the number of injection and production VFP tables, respectively WELLDIMS specifies the number of wells and groups in the model. This keyword is required.
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- 92. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 92 of 499 08/04/99 Data Files with No RUNSPEC Figure 28: Fast Restart File Structure • All data files require a RUNPSEC section except for fast restarts • In a fast restart the RUNSPEC, GRID, EDIT, PROPS and REGIONS sections are read from a SAVE file from a previous run • LOAD passes control to the SOLUTION section, which should be empty except for the RESTART keyword. LOAD --SAVE FILE SIMULATE FORMATTED/ OUTPUT --NAME OR CHECK UNFORMATTED SAVE FILE? -- DATA SAVE FILE? BASE T / RESTART --FILE REPORT --NAME STEP BASE 11 / SUMMARY --THE SUMMARY SECTION IS OPTIONAL SCHEDULE ….. ….. ….. --INCLUDE files containing additional wells, surface facilities --and simulation advance are often entered here END
- 93. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 93 of 499 08/04/99 Data Files with No RUNSPEC All data files need a RUNSPEC section in some form. Fast restart files read a SAVE file containing the RUNPSEC, GRID, EDIT, PROPS, and REGIONS sections and keywords in coded form. A restart run is a means of running a simulation from any report date of a previous simulation. There are two types of restart: full and fast. Full restarts are discussed in a later section. How to Create a Fast Restart • Run a base case simulation. Request output of a SAVE file using the SAVE keyword in RUNSPEC and ensure that restart files are output at the required simulation dates. • Copy the base case data file. Delete everything in it up to the SUMMARY or SCHEDULE keyword, whichever is first in the file. • Insert the LOAD keyword at the beginning of the data file. Choose the LOAD keyword arguments according to whether the current simulation is a data checking run, the input save file is formatted or unformatted and whether another .SAVE file is to be written. • Choose a reporting step from which to continue the simulation • Insert the RESTART keyword after LOAD. • Insert the SKIPREST keyword in the SCHEDULE section after any VFP table specification. This instructs ECLIPSE to skip the periods up to the modified simulation start date. Alternatively, remove the simulation advance keywords (TSTEP, DATES) up to the new start date. • Run the restart simulation as normal.
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- 96. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 96 of 499 08/04/99 Basic Unix Commands Figure 29: The console • The following sections rely on some familiarity with the Unix operating system • The more commonly used Unix commands are presented here with some examples • Unix varies slightly between platforms and versions but the differences are not usually large • PC operating systems are not discussed because interactive application launchers on PC platforms make knowledge of the operating system redundant
- 97. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 97 of 499 08/04/99 Basic Unix Commands Command Comments File Management cd Change directory e.g. cd /ecl/96a/eclipse/data or cd ../eclipse/data cd .. moves to parent directory cp Copy files e.g. cp TEST.DATA TEST2.DATA cd Move to home directory pushd Move to directory and place previous location on stack e.g. pushd $ECLARCH/macros to go to the directory containing the licence file popd Move to previous directory in stack. pwd Shows current location ls List files in current directory e.g. ls –al for a detailed listing including hidden files mv Move or rename files. Paths may be relative or absolute e.g. mv base.data BASE.DATA to convert to upper case. rm Delete files and / or directories e.g. rm –r * to remove everything below current directory including sub-directories mkdir Create a directory e.g. mkdir exercise1 rmdir Remove directory e.g. rmdir exercise1 touch Create file e.g. touch BASE.DATA file Interrogate file type e.g. file BASE.DATA cat Show file contents on screen e.g. cat BASE.DATA more Display file a page at a time e.g. more BASE.DATA head Show the first n lines in a file e.g. head –20 BASE.DATA tail Show the last n lines in a file e.g. tail –25 TEST.DATA umask Set default file permissions chmod Change file permissions e.g. chmod 777 BASE.DATA chown Change file ownership wc Count lines, words & characters Searching grep Search files for strings e.g. grep string * find Search the file system for filenames e.g find / -name ‘eclipse.exe’
- 98. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 98 of 499 08/04/99 System Status and Communications whoami Login id date System clock hostname Name of computer logged on to at present rsh Remote command execution ping Test for communication e.g. ping 192.123.256.385 telnet Log in to another machine e.g. telnet 192.123.256.385 rlogin Remote login to another machine e.g. rlogin –l guest1 support-ss10 users List of current users df Free disk space du Used disk space e.g. du –ks ./* to show space used by sub-directories Special Symbols ~ Home directory & Run in the background e.g. compress tarfile.tar & | Pipe command directs output from one command into another e.g. tar cf - |(cd ~/outgoing ; tar xvf -) . Current directory e.g. cd . changes nothing. .. Parent directory e.g. cd ../.. to move up two levels * Multiple character wildcard e.g. find . –name ‘*.DATA’ | grep RUNSPEC ? Single character wildcard / Top directory Miscellaneous Commands lpr Send file to printer e.g. lpr –Ppostp TEST.DATA tar Create, view or extract archive file e.g tar cvf tarfile.tar . to archive all in current directory. compress Z compress files e.g. compress tarfile.tar uncompress Extract Z compressed files e.g uncompress tarfile.tar.Z vi Terminal-independent text editor kill Terminate processes e.g. kill –9 1234 man View manual page on a commands e.g. man tar clear Clear the screen alias Represent long commands by shorter ones e.g. alias h ‘history !*20’ history List previous commands
- 99. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 99 of 499 08/04/99 su Assume root privileges
- 100. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 100 of 499 08/04/99 The vi Editor Figure 30: The vi device-independent editor • vi is commonly used because it is the same on all platforms • vi offers quite comprehensive text editing functions • vi is keyboard driven; there are no pull-down menus • Some find the keystrokes difficult to memorise • Most Unix systems contain alternative text editors
- 101. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 101 of 499 08/04/99 The vi Editor Insert Mode a append after cursor A append at end of line i insert before cursor I insert at beginning of line o open a line below current line O open a line above current line s substitute a character S substitute entire line Movement Commands: Characters h, j, k, l left, down, up, right Movement Commands: Text w, W, b, B forward ,backward, by word e, E end of word ),( beginning of next, current sentence },{ beginning of next, current paragraph ]],[[ beginning of next, correction section Movement Commands: Lines 0,$ first, last position of current line +. - first character of next, previous line RETURN first character of next line n | column n of current line H top line of screen M middle line of screen L last line of screen Searches /text search forward for text n repeat previous search N repeat search in opposite direction / repeat forward search ? repeat previous search backward
- 102. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 102 of 499 08/04/99 Line numbering nG move to line number n G move to last line in file :n move to line number n Changing and deleting text cw change word cc change line dd delete current line ndd delete n lines D delete remainder of line dw delete word d^ delete to beginning of line dL delete to last line of screen dG delete to end of file p insert last deleted text after cursor P insert last deleted text befor cursor rx replace character with x s substitute character 4s substitute 4 characters S substitute entire line u undo last change U restore current line x delete current cursor position X delete back one character 5X delete previous five characters . repeat last change Copying and moving yw copy word yy copy current line ye copy to end of word p,P put copied text after, before cursor Saving and exiting ZZ quit vi, writing the file only if changes
- 103. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 103 of 499 08/04/99 were made :wq write and quit file :w write the file, do not quit :w file save copy to file :q quit file
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- 106. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 106 of 499 08/04/99 Purpose of the GRID Section Figure 31: Minimum GRID section contents • Reservoir geometry and basic rock properties • Grid cell dimensions and depths, DX, DY, DZ, TOPS, or else COORD and ZCORN • This data is used to establish which cells are connected as regards fluid flow. • Porosity and net-to-gross for each cell, PORO, NTG • Permeabilities for each cell, PERMX, PERMY,PERMZ or PERMR, PERMTHT, PERMZ • Transmissibility modifiers – “MULT” keywords • This is used to create arrays of pore volume, depth and transmissibility for each cell • The above list is the minimum required for this to be possible • Numerical and grid aquifers must be specified in the GRID section. • Optional active cell definition (ACTNUM keyword), pinchout controls and minimum active cell pore volume • Refer to the Grid Section Keyword Summary for a list of the available keywords Grid dimensions & cell depths DX or DXV, DY or DYV, DZ, TOPS or COORD, ZCORN Porosity PORO Permeability PERMX, PERMY, PERMZ or PERMR, PERMTHT, PERMZ Net-to gross or net thickness NTG or DZNET (defaults to 1) For each grid cell in the model
- 107. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 107 of 499 08/04/99 Purpose of the GRID Section ECLIPSE does not use grid cell dimensions and properties for the calculation of fluid flows. Instead, the cell pore volume and transmissibility are used. Enough data must be supplied for ECLIPSE to be able to calculate these quantities for each cell. The definition of pore volume is φ××××= NTGDZDYDXPV EQ. 1 Where the symbols have their usual meanings. So, the dimensions of every cell in X, Y and Z have to be supplied either via the keywords DX or DXV, DY or DYV, DZ, for block- centred geometry or via COORD and ZCORN for corner-point geometry. A value of porosity must also be set for every cell using the PORO keyword but the net to gross (keyword NTG) defaults to 1 for each cell. From Darcy’s equation P L KA Q ∆= µ 1 EQ. 2 This applies to horizontal single phase flow in one direction at surface conditions. The term KA/L can be identified with a property that describes the ease with which fluid may flow between cells in a simulation grid. This is known as the transmissibility. ECLIPSE requires the transmissibility in X, Y and Z directions for each cell to calculate the flows in three dimensions, for which the permeabilities and cell dimensions are needed. As the net to gross affects the area available for flow from cell to cell, it must be taken into account in the transmissibility calculation. So the transmissibility takes the form L NTGKA T × = EQ. 3 In the X direction, for instance, DX NTGDZDYK T x x ... = EQ. 4 The grid cell geometry can be specified either in block-centred or corner point format. Block-centred geometry uses the DX, DY, DZ and TOPS keywords. Block-centred cells are
- 108. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 108 of 499 08/04/99 rectangular and have horizontal upper and lower surfaces and vertical sides. Corner point geometry uses the COORD and ZCORN keywords. Corner point cells can take a much wider variety of shapes, which eases modelling of complex geological structures such as sloping faults, pinchouts and erosion surfaces. Corner point geometry descriptions are much more complex than block-centred and the data is usually much more voluminous. A pre-processor such as GRID is generally used to generate the data. The two different types of geometry cannot be mixed in the same data file because the methods of calculating the transmissibility are different for block-centre and corner- point geometry. The calculation methods are discussed in detail in the sections “Cartesian Grid” p.138 and “Radial Grid” p.146. Although transmissibilities cannot be set explicitly in the GRID section, they can be modified in a number of ways that are discussed further in this section.
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- 110. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 110 of 499 08/04/99 Data Reading Convention Figure 32: Grid data reading convention Cartesian Grids • The origin is in top left-hand corner • In the X-direction numbers increase across the page • In the Y-direction numbers increase down the page • In 3-D, blocks and nodes are ordered left to right, back to front, top to bottom • The grid origin is not necessarily at the corner of cell (1, 1, 1) • The X, Y and Z axes are not necessarily parallel to the I, J, K directions Radial Grids • The origin is the centre of the model • In the R-direction, the innermost ring is ring 1, and the numbers increase outwards • The angle theta is measured in the clockwise direction • The Z direction is unchanged Cell data is read I cycling fastest, followed by J then K
- 111. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 111 of 499 08/04/99 Data Reading Convention For data that takes a single value per cell the following conventions apply: • The first cell read or written is numbered (1, 1, 1) • For Cartesian grids cell (1, 1, 1) is taken to be at the top, back, left of any graphical display • For radial grids cell (1, 1, 1) is close to the centre of the model. • For Cartesian grids the cell data is read in order X cycling fastest followed by Y then Z • For radial grids the cell data is read in order R cycling fastest followed by THETA then Z • All GEOQUEST Simulation Software uses this convention. As an illustration, a model of 20*5*10 as in Figure 32 will have these extents specified in the RUNSPEC section. ECLIPSE will expect to read the geometry data for a total of 1000 cells plus property data to calculate the pore volume and transmissibilities for each cell. The first 20 porosity values read by ECLIPSE will be assumed to be from cell (1, 1, 1) to (20, 1, 1) i.e. the uppermost back row of the model. The next 20 porosity values will apply to cells (21, 1, 1) to (40, 1, 1) inclusive which is the next row forwards on the top layer.
- 112. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 112 of 499 08/04/99 Figure 33: Radial data reading convention Data is read in the same I, J and K order in radial and Cartesian models. In radial models, however, R replaces X and θ replaces Y. Z remains unchanged. 1, 1, 1 2, 1, 1 3, 1, 1 1, 2, 1 2, 2, 1 3, 2, 1 Z 1, 3, 1 1, 4, 1 2, 4, 1 2, 3, 1 3, 4, 1 3, 3, 1 θ R Cell data is read R cycling fastest followed by θ then Z.
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- 114. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 114 of 499 08/04/99 Geometrical Representations Figure 34: Block-centred and corner-point geometries • ECLIPSE supports two types of geometrical description • Block-Centred (BC) Geometry • Corner-Point (CP) Geometry • Each has advantages and disadvantages • Choice of BC or CP depends on the type of model • BC and CP geometries cannot both be used in the same data file DX DZ DY TOPS is the upper face depth Corner depths specified in ZCORN X, Y, Z specified by COORD
- 115. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 115 of 499 08/04/99 Geometrical Representations There are two ways to define dimensions and depths of each grid cell. Block Centred Geometry Block Centred (BC) geometry requires for each cell a top depth plus a cell size in the X, Y and Z directions. The upper and lower faces are flat and horizontal and the cell sides are flat and vertical. The cells are all rectangular. Keywords used to specify Cartesian BC geometry are TOPS, DX (or DXV), DY (or DYV) and DZ. Keywords used to specify radial BC geometry are DR (or DRV), DTHETA (or DTHETAV) and DZ. Keywords ending in a V are the vector format keywords which are the vector equivalents of their standard alternatives. Since each cell is defined using only four real numbers, BC geometrical descriptions tend to be less voluminous than their CP equivalents. Simple models using BC geometry can even be constructed without the use of a pre-processor such as GRID. Consider adjacent BC cells. In a sloping structure, then their TOPS depths will be different. Likewise, the TOP depths of cells either side of a fault will be different. BC geometry effectively ignores the distinction between a slope and a fault. For example, without a structure map as guide, a cross-section such as in Figure 35 could be either sloping or heavily faulted. Figure 35: Sloping structure with fault represented in block centred geometry I or J K Direct connection generated by default by Eclipse
- 116. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 116 of 499 08/04/99 BC geometry does not contain enough information to calculate the overlapping area between neighbouring cells. This is because the cell corner depths are unknown. Fluids usually flow between neighbouring cells so a connection needs to be established. ECLIPSE assumes that cells having neighbouring indices, such as those linked by arrows in Figure 35 are connected even though they should not be. Also, the cells that appear to have overlapping faces in Figure 35 are in reality not connected. This is a result of making no distinction between faults and dip changes in BC geometry. Corner Point Geometry Corner point (CP) geometry is based on the notion of co-ordinate lines and corner depths. A co-ordinate line defines each edge of each column of cells. Co-ordinate lines are always straight but need not be vertical. The X, Y and Z locations of one point above and one point below the grid define each co-ordinate line. Cells are then defined by fixing their corners at set elevations along each co-ordinate line. This permits the cells to have any physically valid shape: sloping surfaces, fault planes, pinchouts and erosion surfaces can be represented correctly. Since each cell is defined by four co- ordinate lines and eight corner depths CP geometry tends to be more voluminous than the BC equivalent and almost always requires a pre-processor such as GRID for construction. Figure 36: Sloping structure with fault represented in corner point geometry I or J K No interblock flow No interblock flow
- 117. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 117 of 499 08/04/99 CP geometry contains enough information to calculate the overlap between adjacent cells since the cell corner depths are known. This means that in Figure 36 only those cells that visibly share an interface are in fact in communication. So, fluids in the cells indicated by arrows cannot flow across the fault. Corner Point versus Block Centred Geometry CP and BC have their respective advantages and disadvantages. The following table summarises them: BC CP Cell description is simple Cell description is complex Pre-processor is not always essential Pre-processor is essential Compatible with many other simulators Compatible with few other simulators Difficult to model irregular structures Irregular structures are modelled accurately Geometry data is not large Geometry data is large Cannot distinguish dip from faulting Distinguishes dip from faulting Pinchouts and erosion surfaces are difficult to model faithfully Pinchouts and erosion surfaces are modelled faithfully Establishes incorrect cell connections across fault planes. Hand modifications are required. Layer contiguity across fault planes is accurately modelled Radial models are easy to construct Radial models are very difficult to construct without a pre-processor
- 118. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 118 of 499 08/04/99 Block-Centred Geometry Example Figure 37: Example block-centred geometrical representation • The model is a 20 * 5 * 10 sector • The model slopes in two dimensions from (1, 1, 1) which is the shallowest cell. • Blocks are 300 ft in X by 1000 ft in Y • Layer thicknesses are 32, 22, 20, 4, 32, 4, 26, 26, 4, 28 ft from the top downwards • This is derived from a CP example shown on on page 122
- 119. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 119 of 499 08/04/99 Block-Centred Geometry Example The following keywords contain the entire geometrical description of the structure in Figure 37: TOPS --The first 20 TOPS define (1, 1, 1) to (20, 1, 1) 6855.000 6865.000 6875.000 6885.000 6895.000 6905.000 6915.000 6925.000 6935.000 6945.000 7005.000 7015.000 7025.000 7035.000 7045.000 7055.000 7065.000 7075.000 7085.000 7095.000 --The next 20 TOPS define (1, 2, 1) to (20, 2, 1) 6930.000 6940.000 6950.000 6960.000 6970.000 6980.000 6990.000 7000.000 7010.000 7020.000 7080.000 7090.000 7100.000 7110.000 7120.000 7130.000 7140.000 7150.000 7160.000 7170.000 --The next 20 TOPS define (1, 3, 1) to (20, 3, 1) 7030.000 7040.000 7050.000 7060.000 7070.000 7080.000 7090.000 7100.000 7110.000 7120.000 7180.000 7190.000 7200.000 7210.000 7220.000 7230.000 7240.000 7250.000 7260.000 7270.000 --The next 20 TOPS define (1, 4, 1) to (20, 4, 1) 7130.000 7140.000 7150.000 7160.000 7170.000 7180.000 7190.000 7200.000 7210.000 7220.000 7280.000 7290.000 7300.000 7310.000 7320.000 7330.000 7340.000 7350.000 7360.000 7370.000 --The next 20 TOPS define (1, 4, 1) to (20, 4, 1) 7205.000 7215.000 7225.000 7235.000 7245.000 7255.000 7265.000 7275.000 7285.000 7295.000 7355.000 7365.000 7375.000 7385.000 7395.000 7405.000 7415.000 7425.000 7435.000 7445.000 / This completes TOPS for the first layer --No more TOPS are needed. Eclipse will add the DZ values --to TOPS to calculate TOPS for successive layers DX --All cells have DX=300. 1000*300 / DY --All cells have DY=1000 1000*1000 / EQUALS
- 120. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 120 of 499 08/04/99 --Set DZ layer by layer --ArrayValue I1 I2 j1 j2 k1 k2 ’DZ’ 32 1 20 1 5 1 1 / ’DZ’ 22 1 20 1 5 2 2 / ’DZ’ 20 1 20 1 5 3 3 / ’DZ’ 4 1 20 1 5 4 4 / ’DZ’ 32 1 20 1 5 5 5 / ’DZ’ 4 1 20 1 5 6 6 / ’DZ’ 26 1 20 1 5 7 7 / ’DZ’ 26 1 20 1 5 8 8 / ’DZ’ 4 1 20 1 5 9 9 / ’DZ’ 28 1 20 1 5 10 10 / /
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- 122. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 122 of 499 08/04/99 Corner Point Geometry Example Figure 38: Example corner-point geometrical representation • The grid is the CP version from which the BC grid on p.118 is derived • Co-ordinate lines define the vertical or sloping edges of the cells • Neighbouring cells share co-ordinate lines • The COORD keyword contains this information • There are eight corners per cell • The ZCORN keyword contains this information
- 123. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 123 of 499 08/04/99 Corner Point Geometry Example The following keywords are a small fraction of the data required to specify the geometry of the structure in Figure 38. COORD --This defines the co-ordinate lines --X1 Y1 Z1 X2 Y2 Z2 0. 0. 6825.000 0. 0. 7023.000 300.0000 0. 6835.000 300.0000 0. 7033.000 600.0000 0. 6845.000 600.0000 0. 7043.000 900.0000 0. 6855.000 900.0000 0. 7053.000 1200.000 0. 6865.000 1200.000 0. 7063.000 .......... .......... .......... / For a 20 * 10 model, 21*11 co-ordinate lines are required, i.e. 231. --Each is defined by 6 numbers so 1386 numbers follow the COORD keyword. ZCORN --This defines the cell corner depths in order X (or R) cycling fastest --then Y (or THETA) then Z 6825.000 6835.000 6835.000 6845.000 6845.000 6855.000 6855.000 6865.000 6865.000 6875.000 6875.000 6885.000 6885.000 6895.000 6895.000 6905.000 6905.000 6915.000 6915.000 6925.000 6975.000 6985.000 6985.000 6995.000 6995.000 7005.000 7005.000 7015.000 7015.000 7025.000 7025.000 7035.000 7035.000 7045.000 7045.000 7055.000 7055.000 7065.000 7065.000 7075.000 ............ ............ ........... / For 1000 cells, 8000 ZCORN values are required --These are just a few
- 124. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 124 of 499 08/04/99 Grid Cell Properties Figure 39: Grid cell property definition • Parameters that describe the dimensions and depth of each grid cell are referred to as geometry parameters • Keywords used to specify geometry parameters are TOPS, DX (or DXV), DY (or DYV), DZ for Cartesian geometry and TOPS, DR (or DRV), DTHETA (or DTHETAV) and DZ for radial geometry or else COORD and ZCORN. • Parameters that describe porosity, permeability, etc. are referred to as properties • Keywords used to specify properties are PORO (φ), PERMX (Kx), PERMY (Ky), PERMZ (Kz) • Net to gross can be specified using either NTG (net to gross ratio) or DZNET (net thickness). • The keyword used to specify explicitly whether a cell is active or not is ACTNUM. It is zero for inactive cells, unity for active cells. Cell properties such as PORO, PERMX, PERMY, PERMZ, NTG are averages defined at the centre
- 125. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 125 of 499 08/04/99 Grid Cell Properties The property keywords require one value per cell. There are a large number of different ways in which these values can be specified using different combinations of ECLIPSE keywords. Property values are taken to be at the cell centres and are an average of the property over each cell volume. The averaging takes place before the data is entered into ECLIPSE, and the means of averaging is decided by the user. Note also that although some cells may be excluded from the simulation (inactive cells), the data to compute their pore volumes and transmissibilities must still be supplied. This is because ECLIPSE contains facilities for deactivating cells based on their minimum pore volume. It is a rule in ECLIPSE that data is supplied as explicit values. ECLIPSE has no facilities for entering data in the form of a function. So, for instance, the porosity cannot be directly entered as a function of permeability. The porosity values would have to be generated using a pre-processor such as GRID and the data for each cell would then be imported into ECLIPSE.
- 126. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 126 of 499 08/04/99 How to Assign Grid Cell Properties Figure 40: Inputting grid data • How to Set One Property Value per Grid Cell • How to Set Grid Cell Property Values Using Boxes • How to Set Grid Cell Property Values Using EQUALS • How to Copy Grid Cell Property Data • How to Add, Subtract, Multiply and Divide Grid Cell Property Data • How to Multiply Cell Pore Volume Using MULTPV • How to Copy Data From one Portion of the Grid to Another using COPYBOX • How to Read Data from Another File Using INCLUDE • How to Deactivate Cells Using ACTNUM I or X K or Z Horizontal permeability is 10, 5, 100, 2000, 200, 2000, 100, 50, 2000, 50 from top to bottom. The model is 20*1*10 in I, J, K, respectively. EQUALS --Array Val I1 I2 J1 J2 K1 K2 ’PERMX’ 2000/ ’PERMX’ 10 1 20 1 1 1 1 / ’PERMX’ 5 1 20 1 1 2 2 / ’PERMX’ 100 1 20 1 1 3 3 / ’PERMX’ 200 1 20 1 1 5 5 / ’PERMX’ 100 1 20 1 1 7 7 / ’PERMX’ 50 1 20 1 1 8 8 / ’PERMX’ 50 1 20 1 1 10 10 / /
- 127. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 127 of 499 08/04/99 How to Assign Grid Cell Properties How to Set One Property Value per Grid Cell The typical format is KEYWORD Value1 value2 value3……..value(NX*NY*NZ) / for example, PERMX --K=1 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 --k=2 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 --k=3 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 --k=4 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 k=5 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 --k=6 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 --k=7 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 --k=8 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 --k=9 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 --k=10 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 Multiple values can be specified using the asterisk, for example PERMX
- 128. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 128 of 499 08/04/99 20*10 20*5 20*100 20*2000 20*200 20*2000 20*100 20*50 20*2000 20*50 / For the above 20*1*10 model. How to Set Grid Cell Property Values Using Boxes The input box is defined by a range of I, J and K values and refers to a rectangular block of cells. The box can refer to a region, a layer, a column or a row of cells. Any grid property can be set for the cells within the box. A value must be specified for each cell in the box, including those at the ends of the range. The box remains in effect until either a new box is read in or the ENDBOX keyword is read. The new box closes the previous box and opens another. The default box is the entire set of cells. For instance: BOX --I1 I2 J1 J2 K1 K2 1 20 1 1 1 10 / PERMX 20*2000/ ENDBOX Sets PERMX to 100 for cells (1,1,1), to (20, 1, 10) i.e. throughout the model. Smaller boxes could then be used to set the permeability layer by layer: For layer 3, for example BOX --I1 I2 J1 J2 K1 K2 1 20 1 1 3 3 / PERMX 20*100 / ENDBOX This will overwrite any PERMX values specified earlier for layer 3. How to Set Grid Cell Property Values Using EQUALS The EQUALS keyword operates on properties as arrays and can be used as an alternative to the BOX keyword. EQUALS can be applied to the last example to set PERMX for layer 3 :
- 129. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 129 of 499 08/04/99 BOX --I1 I2 J1 J2 K1 K2 1 20 1 1 3 3 / EQUALS ‘PERMX’ 100 / ENDBOX EQUALS can also be used to define a box without using the BOX keyword explicitly. For instance: EQUALS --Arrayvalue I1 I2 J1 J2 K1 K2 ‘PERMX’2000 / defaults to currently open box -- i.e. entire reservoir ‘PERMX’10 1 20 1 5 1 1 / ‘PERMX’5 1 20 1 5 2 2 / ‘PERMX’100 1 20 1 5 3 3 / ‘PERMX’200 1 20 1 5 5 5 / ‘PERMX’100 1 20 1 5 7 7 / ‘PERMX’50 1 20 1 5 8 8 / ‘PERMX’50 1 20 1 5 10 10 / / defines PERMX throughout the section. The box is opened as part of the EQUALS keyword and is closed by the second forward slash (/) which exits the EQUALS keyword. To ensure that values are specified for each and every cell, it is advisable to specify values for the entire grid before overwriting them selectively using BOX and EQUALS.
- 130. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 130 of 499 08/04/99 Figure 41: Copying, Adding and Multiplying Data How to Copy Grid Cell Property Data The COPY keyword is used to copy data from one array to another in the current box. If the permeability is uniform throughout the field, this can be set as follows provided the current box is the entire field: COPY ’PERMX’’PERMY’ / ’PERMX’’PERMZ’ / / If the permeability is isotropic only in a certain region, then the BOX keyword can be used in combination with COPY. For instance: BOX --I1 I2 J1 J2 K1 K2 1 20 1 5 1 1 / COPY ‘PERMX’‘PERMY’ / ‘PERMX’‘PERMZ’ / / COPY --Source Destination ’PERMX’ ’PERMY’ / ’PERMX’ ’PERMZ’ / / MULTIPLY --Array Value I1 I2 J1 J2 K1 K2 ’PERMZ’ 0.1 / No box limits set; defaults to previous open box / This forward slash ends the MULTIPLY keyword --To divide, multiple by the reciprocal ADD --Array Value I1 I2 J1 J2 K1 K2 ’PORO’ 0.1 / / This forward slash ends the ADD keyword --To subtract, add the negative
- 131. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 131 of 499 08/04/99 ENDBOX Any number of arrays can be copied within the COPY keyword. How to Add, Subtract, Multiply and Divide Grid Cell Property Data The general format for these operations is <OPERATION> ‘KEYWORD’ Value I1 I2 J1 J2 K1 K2 / ‘KEYWORD’ Value I1 I2 J1 J2 K1 K2 / ‘KEYWORD’ Value I1 I2 J1 J2 K1 K2 / / or alternatively BOX I1 I2 J1 J2 K1 K2 / <OPERATION> ‘Keyword’ Value / ‘Keyword’ Value / ‘Keyword’ Value / ENDBOX Any number of arrays can be adjusted The box limits are optional. If a property is to be adjusted over the entire model, they would be absent in the first example and the BOX and ENDBOX keywords would be absent from the second. For instance, permeability is not usually isotropic and is often represented by a Kv/Kh ratio of 0.1. This could be defined as follows over the entire field as: MULTIPLY --Keyword Value I1 I2 J1 J2 K1 K2 ‘PERMZ’ 0.1 / No box limits set – defaults to previous open box / --This forward slash ends the MULTIPLY keyword To set a Kv/Kh ratio over the first layer only, for instance, use: MULTIPLY --Keyword Value I1 I2 J1 J2 K1 K2 ‘PERMZ’ 0.1 1 20 1 5 1 1 / / --This forward slash ends the MULTIPLY keyword or else BOX --I1 I2 J1 J2 K1 K2 1 20 1 5 1 1 / MULTIPLY --Array Value ‘PERMZ’ 0.1 /
- 132. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 132 of 499 08/04/99 ENDBOX To divide a property by some value, multiply by the reciprocal. These operations are cumulative. So, a multiplier of 10 followed by a multiplier of 2 will result in a total multiplier of 20 Addition is very similar. For instance, to add 0.05 to the porosity in the same box as above use: ADD --Keyword Value I1 I2 J1 J2 K1 K2 ‘PORO’ 0.05 1 20 1 5 1 1 / / --This forward slash ends the ADD keyword or else BOX --I1 I2 J1 J2 K1 K2 1 20 1 5 1 1 / ADD --Array Value ‘PORO’ 0.05 / ENDBOX To subtract a value, add the negative. How to Multiply Cell Pore Volume Using MULTPV Cell pore volume can be multiplied by any factor using the MULTPV keyword. For instance, MULTPV 200*1.01 / will increase the pore volume of the first 200 cells by 1%. This may be necessary, for instance, to ensure the simulated fluids in place (FIP) correspond to estimates from other sources. Note, however, that the greater the pore volume, the higher the degree of pressure support provided by a cell. Pore volumes should therefore not be varied significantly and matching of the overall pressure behaviour of the reservoir should take place after pore volume multipliers have been applied. Pore volume multipliers are sometimes used during history matching to help attain either or both of these aims. How to Copy Data From one Portion of the Grid to Another using COPYBOX Data can be copied from one part of the reservoir to another using the COPYBOX keyword. The source and destination boxes must be the same size in the I, J, and K directions. The general form is:
- 133. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 133 of 499 08/04/99 COPYBOX Keyword Source box Destination box / / For instance, to copy the porosity and x direction permeability from layer 1 to layer 2 use: COPYBOX --Keyword I1S I2S J1S J2S K1S K2S PORO 1 20 1 5 1 1 --I1D I2D J1D J2D K1D K2D 1 20 1 5 2 2 / PERMX 1 20 1 5 1 1 1 20 1 5 2 2 / / How to Read Data from Another File Using INCLUDE Data can be read directly into the ECLIPSE data file from an external file using the INCLUDE keyword. The file can be located anywhere on the file system and can be referred to by an absolute or relative pathname. No path needs to be specified if the file is in the same directory as the ECLIPSE data file it is being read into. All of the following examples are valid provided the paths and files exist: INCLUDE COORD.GRDECL / INCLUDE ZCORN.GRDECL / INCLUDE ‘../../GRID/PERMX.GRDECL’ / INCLUDE ‘/tiny/user/hm2/griddata/outputs/PORO.GRDECL’ / INCLUDE can be used anywhere in the data file and is the usual means of importing large amounts of data. Quotes are required if the pathname contains any characters that ECLIPSE might have ambiguous interpretations, such as forward slashes and full stops. On Unix systems the filename is case sensitive Included files can be nested, that is included files can contain the INCLUDE keyword. The INCLUDE keyword may not be used within another keyword. How to Deactivate Cells Using ACTNUM Any cell can be explicitly deactivated using the ACTNUM keyword.
- 134. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 134 of 499 08/04/99 ACTNUM is a grid cell property array so it can be used in any of the examples above ACTNUM can only take two values: 0 denotes an inactive cell, 1 denotes an active cell Pre-processors such as GRID are frequently used to define ACTNUM for inclusion in ECLIPSE. Inactive cells are removed from the simulation. ECLIPSE does not calculate the flows in those cells. The graphical output, however, is largely unchanged since the cell locations remain unaltered. ECLIPSE must have enough information to calculate the pore volume, depth and transmissibility of the inactive cells even though they are inactive. PORO, PERMX etc. must still be defined for inactive cells. Inactive cells are referred to in outputs. There is very little data associated with inactive cells since most quantities are undefined; the values are listed as several hyphens.
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- 136. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 136 of 499 08/04/99 Transmissibility Conventions Figure 42: Transmissibility conventions • Transmissibility is a property shared by connected cells • Transmissibility controls the amount of fluid flow from cell to cell. • To determine how to modify transmissibilities, it is important to know how transmissibility is assigned • Transmissibility in ECLIPSE is calculated between one cell and the next cell in the positive i.e. upstream, direction. • Tx i,j,k is between cell (I, J, K) and cell (I+1, J, K) in the I direction • Ty i,j,k is between cell (I, J, K) and cell (I, J+1, K) in the J direction • Tz i,j,k is between cell (I, J, K) and cell (I, J, K+1) in the K direction • The diagram shows examples of direct connections • A direct connection represents flow between cells having neighbouring IJK indices • Each cell has six direct connections. From cell (I, J, K) they are to (I-1, J, K), (I+1, J, K), (I, J-1, K), (I, J+1, K), I, J, K-1), (I, J, K+1). Ty311 Tx 111 Tx 211 Tx 121 Tx 221 Tx 131 Tx 231 Ty 111 Ty 121 Ty 211 Ty 121 Ty 311 Ty 321 I J K=1
- 137. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 137 of 499 08/04/99 Transmissibility Conventions Transmissibility is a property shared between connected cells, i.e. cells between which fluids may flow. In a system of discrete grid cells fluid flow is calculated between the centres of the grid blocks. The extent of this flow is determined by the transmissibility and mobility between connected cells, and how those quantities are calculated and assigned. Consider the flow between two adjacent cell centres. The transmissibility must account for the cell properties in each cell i.e. it has to be some form of average of the properties of both cells which also accounts for the cell geometry and overlapping area. The variations on transmissibility calculation used by ECLIPSE are described in the following sections. Some are more appropriate for certain types of geometry than others. All transmissibility calculations, however, are in the upstream direction i.e. the transmissibilities assigned to cell (I, J, K) govern the flows to cells (I+1, J, K), (I, J+1, K) and I, J, K+1). NOTE. The assignment of mobility between adjacent cells does not follow the same convention. In calculating the mobility for flow between two cells the available mobilities are of the current cell, the upstream cell and an average of the two. Of these, the upstream mobility has been found to be the most reliable [1]. This is superficially counter-intuitive because the mobility used should be the average mobility of the fluid flowing between the blocks at any particular time. By Darcy’s Law for each phase, however, this fluid comes from the block with the larger phase potential. Use of the upstream mobility assumes that the upstream block contains “stirred” fluid so that the mobility of fluid travelling across the cell interface is the same as the mobility of the fluid at the cell centre. Mattax, C. C., Dalton, R. L., “Reservoir Simulation”, SPE Monograph v.13[2]
- 138. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 138 of 499 08/04/99 Cartesian Grid Transmissibility Figure 43: Cartesian grid transmissibility as viewed using GRAF • Transmissibility is calculated differently in block-centred and corner-point geometries • Radial and Cartesian transmissibilities are also calculated differently. • The calculation methods are invoked using keywords OLDTRAN (block centred), NEWTRAN (corner point), OLDTRANR (as in the BETAII simulator) • If OLDTRAN, OLDTRANR or NEWTRAN is not specified, ECLIPSE uses OLDTRAN for BC geometry and NEWTRAN for CP geometry automatically. • OLDTRAN is the (harmonic average of permeability)*(arithmetic average of area) • OLDTRANR is the harmonic average of (permeability*area) • NEWTRAN is the harmonic average of half-cell transmissibilities • The following three sections on transmissibility calculations are intended primarily for use as a reference.
- 139. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 139 of 499 08/04/99 Cartesian Grid Transmissibility The transmissibility between a pair of connected cells is calculated from the cell geometry, permeability and net to gross. The simplest methods are to calculate the flows between two neighbouring cells by considering either the flow between the cell centres (at which the cell properties are averaged) or by integrating the phase potential between two chosen locations. The result is then compared to Darcy’s equation and the portion analogous to KA/L extracted. Depending on the available information on cell geometry and averaging method, one of a number of different calculation methods may be used. NOTE. A detailed exposition on the derivation of transmissibility of Cartesian grid systems can be found in reference .[3] OLDTRAN Transmissibility Calculation Figure 44: OLDTRAN transmissibility definition OLDTRAN is used by default in block centred models. It takes the form DX1 DX2 DZ1 DZ2 Kx1 and NTG1 KX2 and NTG2 A2=DY2.DZ2 (DX1+DX2)/2 T12 Depth D2 Depth D1 A1=DY1.DZ1
- 140. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 140 of 499 08/04/99 12 1212 12 B DCA T x = EQ. 5 where Tx 12 is the x-direction transmissibility between (I, J, K,) and (I+1, J, K), C is the Darcy constant, A12 the interface area between the two cells in the x-direction and D12 a dip correction.. It may also include a user-supplied transmissibility multiplier, which has been omitted here. A12, D12 and B12 are given, respectively, by 21 22221111 12 ...... DXDX NTGDZDYDXNTGDZDYDX A + + = EQ. 6 2 21 2 21 2 21 12 2 2 −+ + + = DD DXDX DXDX D EQ. 7 where D1 and D2 are cell centre depths and += 2 2 1 1 12 2 1 xx K DX K DX B EQ. 8 Then the transmissibility is 2 2 1 121 22221111 1212 2...... xx x K DX K DXDXDX NTGDZDYDXNTGDZDYDX CDT + + + = EQ. 9 or ( ) ( ) + + + + + = 2 2 1 1 21 21 222111 21 12 12 ....2 xx x K DX K DX DXDX DXDX NTGADXNTGADX DXDX CD T EQ. 10 ( ) KA DXDX CD Tx . 2 21 12 12 + = EQ. 11
- 141. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 141 of 499 08/04/99 i.e. the transmissibility is proportional to (arithmetic average of area)*(harmonic average of permeability) with a dip correction. Note that the dimensions used here are simply those supplied by DX, DY and DZ. NOTE that NTG is the net to gross ratio, which appears in the horizontal transmissibilities but is, absent from the Z transmissibility. This becomes significant when modelling shales or similar structures, which restrict flow in the vertical direction. Figure 45: Effect of uneven block sizes in BC geometry OLDTRAN assumes that cells with neighbouring indices are in contact as fully as possible since in block centred geometry the locations of the cell corners are not specified. Although it may seem reasonable to calculate the corner locations, this is will not provide meaningful results in some cases. Consider a model of 3*3*1 with cells uniformly sized in X, Y and Z, except for the central cell, which is much smaller, as shown in Figure 45. Post-processors such as GRAF place cell (2,2,1) at the top, back, left of the available gap between the surrounding cells and calculates the transmissibility as usual. The void has no effect on the ECLIPSE transmissibility calculation. J I (1, 1, 1) (2, 1, 1) (3, 1, 1) (1, 2, 1) (2, 2, 1) (3, 2, 1) (1, 3, 1) (2, 3, 1) (3, 3, 1) VOID
- 142. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 142 of 499 08/04/99 OLDTRANR Transmissibility Calculation Figure 46: OLDTRANR transmissibility definition OLDTRANR is a variation on the OLDTRAN calculation method. Using OLDTRANR the transmissibility takes the form 12 12 12 B CD T x = EQ. 12 It may also include a user-supplied transmissibility multiplier, which has been omitted here. D12, the dip correction and B12 are given respectively by 2 21 2 21 2 21 12 2 2 −+ + + = DD DXDX DXDX D EQ. 13 and DX1 DX2 DZ1 DZ2 Kx1 and NTG1 KX2 and NTG2 A2=DY2.DZ2 (DX1+DX2)/2 T12 Depth D2 Depth D1 A1=DY1.DZ1
- 143. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 143 of 499 08/04/99 += 2222 2 1.111 1 12 .....2 1 NTGKDZDY DX NTGKDZDY DX B xx EQ. 14 Then ( ) ( ) + + + = 2222 2 1.111 1 21 21 12 12 ..... 2 NTGKDZDY DX NTGKDZDY DX DXDX DXDX CD T xx x EQ. 15 rewriting gives ( ) AK DXDX CD Tx 21 12 12 2 + = EQ. 16 where the term in square brackets has been rewritten as the harmonic average of (permeability*area). The dimensions used are those supplied by DX, DY, DZ. In other respects, the behaviour of grids using OLDTRANR is the same as that for OLDTRAN. NOTE that NTG is the net to gross ratio which appears in the horizontal transmissibilities but is absent from the Z transmissibility. This becomes significant when modelling shales or similar structures, which restrict flow in the vertical direction.
- 144. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 144 of 499 08/04/99 NEWTRAN Transmissibility Calculation Figure 47: NEWTRAN transmissibility definition NEWTRAN is the method used by default to calculate transmissibility in corner point geometry. The transmissibility is calculated form the X, Y and Z projections of the interface area of the cells. Using a vector distance from the cell centre to the face automatically incorporates a dip correction. The X direction transmissibility takes the form + = 21 12 11 xx x TT C T EQ. 17 i.e. a harmonic average of the X direction transmissibilities of the two connected cells. It may also include a user-supplied transmissibility multiplier, which has been omitted here. Here 1 2 1 2 1 2 112112112 111 zyx zzyyxx x x DDD DADADA NTGKT ++ ++ = DX1 DX2 Ax12 θx1 θx2 DZ1 DZ2 Kx2 , NTG2 Kx1 , NTG1
- 145. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 145 of 499 08/04/99 EQ. 18 Ax12, Ay12 and Az12 are the X, Y and Z projections of the interface area of cells 1 and 2 and Dx1, Dy1, Dz1 are the X, Y and Z components of the distance between the centre and X face of cell 1. For a rectangular cell the Y and Z projections and components are zero and the X component of the distance from the cell centre to the X direction face is horizontal, so 2 1 1211 1 DX ANTGK T xxx = EQ. 19 or 1 11211 1 2 DX CosANTGK T xxx θ = EQ. 20 where A12 is the shared interface area. The expressions for half-cell transmissibility in the Y and Z directions are similar. NOTE that NTG is the net to gross ratio, which appears in the horizontal transmissibilities but is, absent from the Z transmissibility. This becomes significant when modelling shales or similar structures which restrict flow in the vertical direction. In corner point geometry the cell corner depths are supplied. This is used to calculate the extent of overlap between adjacent cells and provide a better estimate of the transmissibility between adjacent cells either side of a fault. It is also possible to calculate the shared area between adjacent cells, which are not neighbouring.
- 146. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 146 of 499 08/04/99 Radial Grid Transmissibility Figure 48: Radial transmissibility • Radial transmissibility calculation is the same in BC and CP geometry • The expressions are based on radial flow between pressure equivalent radii R2 R1 P1 P2
- 147. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 147 of 499 08/04/99 Radial Grid Transmissibility The radial transmissibility is based on the assumption of true radial flow between the pressure equivalent radii of connected cells and incorporates a dip correction. The pressure equivalent radius of a grid cell is that radius at which the grid block pressure is the same as the pressure calculated from true radial flow. The expression for radial transmissibility takes the form 21 12 12 11 RR R R TT CD T + = EQ. 21 where C is Darcy’s constant and DR 12 the radial dip correction. It may also include a user-supplied transmissibility multiplier, which has been omitted here. Here 5.0ln 1 1 1 2 2 2 1 2 1111 1 + − = R R RR R DZDNTGK T RR θ EQ. 22 and 5.0ln 2 3 2 2 3 2 3 2 2222 2 − − = R R RR R DZDNTGK T RR θ EQ. 23 where R1 is the inner radius of cell1, R2 the outer radius of cell 1 and R3 the outer radius of cell 2. The dip correction is ( )2 21 2 13 2 13 2 2 12 DD RR RR D R −+ − − = EQ. 24 The azimuthal transmissibility is 21 12 12 11 θθ θ θ TT CD T + = EQ. 25 with
- 148. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 148 of 499 08/04/99 ( ) 1 1 2111 1 ln2 θ θ θ D R RDZNTGK T = EQ. 26 where R1 is the inner radius and R2 the outer radius. The azimuthal dip correction Dθ 12is 2 21 2 21 2 21 12 2 2 −+ + + = DD DD DD D θθ θθ θ EQ. 27 The vertical transmissibility is 21 12 11 ZZ z TT C T + = EQ. 28 with ( ) 1 1 2 2 2 11 1 DZ RRDK T zz − = θ EQ. 29 Note that some of these expressions lose validity in some circumstances. For instance if Dθ or DR vary within a cell, as they are permitted to in corner point geometry, then the calculations may become invalid. This would correspond to a sloping radial model.
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- 150. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 150 of 499 08/04/99 Shale Modelling Figure 49: Shale representation • Each lithological layer can be modelled as a separate grid layer • The shales can be incorporated into the sand layers • Shale layers can be modelled as gaps between grid layers Sand Shale Shale Shale Sand Sand Sand Sand K=1 Sand K=3 Sand K=5 Sand K=7 Sand K=1 Sand K=2 Sand K=3 Sand K=4 GAP GAP GAP K Sand / Shale K=1 Sand / Shale K=2 Sand / Shale K=3 Sand K=4 Shale K=2 Shale K=4 Shale K=6 Lithology Explicit shales Shales described with NTG or DZNET Shales as gaps between sand layers
- 151. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 151 of 499 08/04/99 Shale Modelling Three methods are commonly used to model shale barriers of uncertain extent and transmissibility. Each has specific advantages and disadvantages. Modelling shales explicitly as grid layers This has the advantage of precise control over the layer properties. Varying the permeability, which influences the transmissibility, can control the flow across the shale. Although the NTG of a shale barrier is often close to zero, the NTG does not appear in calculations of vertical transmissibility. It does, however, appear in the horizontal transmissibility, so there will be no horizontal flow within such shale. As shales are often relatively thin the pore volume of shale barrier cells is likely to be low compared to the pore volume of adjacent cells. This may cause some or all of the following difficulties: • If the model uses PINCH and / or MINPV keywords to deactivate cells and establish connections across pinched-out cells, shale cells may be removed from the simulation. Cells deactivated by MINPV become barriers to flow. Cells thinner than the pinchout threshold distance are removed from the simulation and the cells either side come into communication as if the shale were absent. Effectively, the former converts the shale to a flow barrier while the latter removes the shale. • Cells of large pore volume next to cells of small pore volume are likely to lead to throughput-related convergence problems. Consider two adjacent cells of pore volume 1 Rb and 1000 Rb. ECLIPSE solves for oil saturation to an accuracy of ±0.001. If the oil saturation has been calculated as 0.5, then the oil in place (OIP) of each cell is 0.5±0.001 Rb and 500±1 Rb. The OIP of one cell is smaller than error on the OIP of the next, that is the larger cell is likely to determine the throughput of the smaller, which may be many times the pore volume of the smaller cell. This is likely to cause convergence problems and should be avoided. • If there is a large number of extensive shale layers, modelling them explicitly may introduce an unreasonably large number of cells into the model, which will greatly influence the run time. Modelling shales by incorporation into larger sand cells Shales may be amalgamated with sand layers. To do this the net sand thickness must be supplied either using the DZNET keyword or NTG where
- 152. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 152 of 499 08/04/99 DZ DZNET NTG = EQ. 30 NOTE that since DZNET and NTG represent the same quantity they cannot be used together. The porosity of the cell should be equivalent to the porosity of the net sand, not the porosity averaged over the entire cell. This method effectively “smears” the shale throughout the cell; the pore volume distribution with height is now incorrect. Also, the vertical transmissibility between the geological shale layer and the adjacent sand layer is no longer zero. The horizontal transmissibility in the location of the shale is no longer zero. The horizontal transmissibility in the region of the sand is reduced. All of these transmissibilities, particularly in the vertical direction, may need to be modified using one or more of the “MULT” keywords. This has the advantage of eliminating throughput-related convergence problems and reducing the number of cells in the simulation. Also, difficulties introduced in not knowing beforehand which cells will be deactivated by MINPV or MINPVV in ECLIPSE are reduced, if not removed. Modelling shales as gaps between sand layers Using some grid-building pre-processors such as GRID it is possible to detach one layer from another. The space between layers K=1 and K=2 is not occupied by a cell; it is a void. The vertical transmissibility between layers K=1 and K=2, however, is not zero. It is calculated in the usual manner and the gap does not affect it. Effectively, the shale layer has been removed and the vertical transmissibility between the layers must be adjusted using MULTZ and / or MULTZ- to reduce or remove the vertical flow. The horizontal transmissibility and pore volume distribution of layers 1 and 2 are as they would be if the shale were modelled explicitly as cells – unchanged. This has the advantages of reducing the number of cells in the simulation, removing throughput- related convergence problems and allowing the vertical flow between layers to be modified independently of the shale porosity and permeability. Its main disadvantage is that if the shale has significant oil content which is extracted over time, this will not be included.
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- 154. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 154 of 499 08/04/99 Transmissibility Modification Figure 50: Modifying transmissibility using MULTX, FAULTS and MULTFLT • Upstream transmissibilities can be set explicitly using the TRANX/Y/Z, TRANR/THT/Z keywords in the EDIT section only. • Upstream transmissibilities can be multiplied using MULTX/Y/R/THT/Z • Downstream transmissibilities can be set explicitly using TRANX-/Y-/Z-, TRANR- /THT-/Z- keywords in the EDIT section only. • Downstream transmissibilities can be multiplied using MULTX-/Y-/R-/THT-/Z-. • Downstream transmissibility multipliers are enabled using GRIDOPTS in RUNSPEC • Transmissibility multipliers do not act upon permeability. • A fault can be defined using the FAULTS keyword. Its upstream transmissibility can be multiplied by the MULTFLT keyword. • Transmissibility multipliers are not cumulative; they affect direct and non- neighbour connections. FAULTS --Name IX1 IX2 IY1 IY2 IZ1 IZ2 FACE --Layers are from 1 to 10 FLT-1 2 4 1 1 1 10 Y / FLT-1 4 4 2 3 1 10 X / FLT-1 5 8 3 3 1 10 Y / FLT-1 8 8 4 4 1 10 X / FLT-2 10 10 1 5 1 10 X / / MULTFLT --Name TMULT ’FLT-1’ 0.0 / / EQUALS --Array Val. I1 I2 J1 J2 K1 K2 ’MULTX’ 0.0 10 10 1 5 1 10 / /Zig-zag fault FLT-1 Straight fault FLT-2
- 155. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 155 of 499 08/04/99 Transmissibility Modification Transmissibility can be modified in a number of ways. One of the simplest is to alter the input permeability. This can be done by either setting the permeability explicitly using the “PERM” keywords or by multiplying the permeability by some known factor using MULTIPLY. This may not always be appropriate. For instance, if a shale barrier of uncertain extent and permeability is modelled as a gap between two layers instead of as cells, the transmissibility across the gap must be adjusted. It can be either set explicitly using TRANZ and/or TRANZ- or multiplied using MULTZ and/or MULTZ-. Behaviour of Transmissibility Modification Keywords The “TRAN” and “MULT” keywords operate on the transmissibility in the direction of increasing cell index, the “TRAN”- and “MULT”- keywords operate in the direction of decreasing cell index. The last two can only be used if the relevant switch in the GRIDOPTS keyword in the RUNSPEC section has been set. • MULTX, MULTY, MULTZ alter transmissibility in the direction of increasing X, Y, Z • MULTX-, MULTY-, MULTZ- alter transmissibility in the direction of decreasing X, Y, Z • MULTR, MULTTHT alter transmissibility in the direction of increasing radius and azimuth (clockwise) • MULTR-, MULTTHT- alter transmissibility in the direction of decreasing radius and azimuth (anti-clockwise). The interaction between transmissibility multipliers can be complex. The following rules should be borne in mind: - • All apply to block-centred and Corner-point geometry • MULTZ and MULTZ- are used in radial and Cartesian models. • The “MULT” multipliers are not cumulative • If the MULTIPLY keyword is used to repeatedly modify transmissibility, then the change is cumulative. • The “MULT” multipliers affect direct or normal connections • The “MULT” multipliers do not affect non-neighbour connections created using the NNC keyword (the explicit NNCs created by the user).
- 156. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 156 of 499 08/04/99 • The “MULT” multipliers affect non-neighbour connections generated by ECLIPSE, e.g. across faults. See the section on Non-Neighbour Connections for more information. • If both upstream and downstream “MULT” multipliers are specified between two cells, then the product of the multipliers is applied to the transmissibility. For instance if MULTX is set for cell (I, J, K) and MULTX- for (I+1, J, K) then the calculated transmissibility between the cells is multiplied by the product of MULTX and MULTX- • The “MULT” multipliers entered in the GRID section only affect transmissibilities calculated in the GRID section. • The “MULT” multipliers entered in the EDIT section affect transmissibilities passed from the GRID section. Numerical and grid aquifers are ways of defining aquifers using some of the cells in the reservoir grid. For this reason, they must be defined in the GRID section. Analytical and flux aquifers do not use existing grid cells and are defined in the SOLUTION section. The section on Aquifer Modelling, p.323 discusses all aquifer modelling facilities in detail. The following table summarises the functions of these keywords. Note that some may only be used in the EDIT section. Keyword Description From To Default value GRID Section EDIT Section TRANX Upstream X transmissibility (I,J,K) (I+1,J,K) From cell geometry & properties Χ á TRANY Upstream Y transmissibility (I,J,K) (I,J+1,K) From cell geometry & properties Χ á TRANR Upstream radial transmissibility (I,J,K) (I+1,J,K) From cell geometry & properties Χ á
- 157. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 157 of 499 08/04/99 TRANTHT Upstream azimuthal transmissibility (I,J,K) (I,J+1,K) From cell geometry & properties Χ á TRANZ Upstream Z transmissibility (I,J,K) (I,J,K+1) From cell geometry & properties Χ á MULTX Upstream X transmissibility multiplier (I,J,K) (I+1,J,K) 1 á á MULTX- Downstream X transmissibility multiplier (I,J,K) (I-1,J,K) 1 á á MULTY Upstream Y transmissibility multiplier (I,J,K) (I,J+1,K) 1 á á MULTY- Downstream Y transmissibility multiplier (I,J,K) (I,J-1,K) 1 á á MULTR Upstream radial transmissibility multiplier (I,J,K) (I+1,J,K) 1 á á MULTR- Downstream radial transmissibility multiplier (I,J,K) (I-1,J,K) 1 á á MULTTHT Upstream azimuthal transmissibility multiplier (I,J,K) (I,J+1,K) 1 á á
- 158. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 158 of 499 08/04/99 MULTTHT- Downstream azimuthal transmissibility multiplier (I,J,K) (I,J-1,K) 1 á á MULTZ Upstream Z transmissibility multiplier (I,J,K) (I,J,K+1) 1 á á MULTZ- Downstream Z transmissibility multiplier (I,J,K) (I,J,K-1) 1 á á The transmissibility of each cell in a named fault can be modified by first defining the fault using the FAULTS keyword then multiplying the upstream transmissibility of all cells adjacent of the fault using MULTFLT as shown in Figure 50.
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- 160. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 160 of 499 08/04/99 Non-Neighbour Connections Figure 51: Sources of non-neighbour connections • A NNC allows flow between cells without adjacent IJK indices. • NNCs are required where flow is expected between cells which are not neighbours • NNC generation is enabled by default. Use NONNC in RUNSPEC to switch it off. • NNCs and the transmissibility across them are generated automatically at: • Faults when NEWTRAN is in use • Pinchouts and erosion surfaces when the PINCH or PINCHOUT keyword is used • Local Grid refinements and Coarsenings • Dual Porosity models • When “completing the circle” in radial models the COORDSYS keyword enables NNC generation and ECLIPSE calculates their transmissibility values • Aquifer NNCs must be specified explicity; ECLIPSE calculates their transmissibility • NNCs can be created explicitly between any pair of grid cells in the model using the NNC keyword. The transmissibility of such NNCs must be set explicitly. Faults Radial Models Analytical Aquifers LGRs & LGCs Explicit NNCs NNCs Dual Poro & Perm Models Pinchouts & erosion surfaces Numerical Aquifers
- 161. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 161 of 499 08/04/99 Non-Neighbour Connections Flow is usually expected between adjacent cells and is modelled as a direct connection between cells with adjacent (I, J, K) indices. Accurate definition of many structures, however, often requires that cells with non-neighbouring (I, J, K) indices have to be located next to one another and that there must be flow between them. An example is the flow across a fault with a significant throw. Other situations that require NNCs are due to the nature of the geometrical descriptions used in ECLIPSE, such as Local Grid Refinements (LGRs) and aquifer connections.
- 162. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 162 of 499 08/04/99 NNC Generation across Faults Figure 52: Fault non-neighbour connections • Fault NNCs are generated automatically unless NONNC is in the RUNSPEC section. • Fault NNCs are generated if NEWTRAN is in use • The transmissibility values are calculated automatically I or J K Graf display of fault NNCs. Eclipse generates these by default. Direct connections not shown
- 163. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 163 of 499 08/04/99 NNC Generation across Faults NNCs are enabled by default and will be created across faults where necessary and possible. In corner point geometry where the NEWTRAN Transmissibility Calculation is used by default NNC generation requires no intervention by the user. The use of OLDTRAN with CP geometry is not recommended because it will suppress NNC generation across faults. In block-centred geometry where the OLDTRAN Transmissibility Calculation is in use by default, ECLIPSE lacks the geometrical information to evaluate whether cells are in reality adjacent across a fault and NNCs are not generated across faults. Although it is possible to use NEWTRAN with BC geometry, this does not provide additional geometrical information.
- 164. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 164 of 499 08/04/99 NNC Generation across Pinchouts Figure 53: Pinchout NNC generation • ECLIPSE allows layers to have zero thickness, which can be used to model pinchouts and erosion surfaces • The PINCH keyword creates NNCs across layers with DZ less than a set threshold provided NONNC is not used. • PINCH contains switches to create NNCs across layers with DZ greater than the threshold if the cells have been deactivated by MINPV. MINPV 5000/ Cell with PV<5000 are deactivated PINCH --Threshold Gap -- Treatment 0.1 ’GAP’ / NNCs generated by PINCH across sufficiently thin layers. DZ may be > 0.1 I or J Direct connections (not shown) are created across this gap between layers K
- 165. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 165 of 499 08/04/99 NNC Generation across Pinchouts Corner point geometry allows cells to have non-rectangular shapes, which is a very powerful facility for accurately modelling pinchouts and erosion surfaces. Although these structures are very different geologically, from the point of view of simulation grid geometry they are defined in the same manner. NNCs are generated across inactive cells having a thickness less than a specified value using the PINCH keyword. For instance, PINCH / will create an NNC between the cells above and below any cell having DZ less than 0.01 feet or metres. However, a number of cells will have been deactivated automatically by ECLIPSE. In the interest of avoiding throughput-related convergence problems, ECLIPSE deactivates all cells having a pore volume less than 10-6 m3, Rb or cc. This limit can be raised, but not lowered, using the MINPV keyword. For instance MINPV 5000 / will deactivate all cells with a pore volume less than 5000 Rb in a model using FIELD units. These cells do not participate in the simulation and the flow equations are not solved for them. By default they are no-flow barriers and there is no guarantee that they will be thin enough for PINCH to create NNCs across them. If the second item of PINCH is set to ’GAP’, then ECLIPSE creates NNCs across cells deactivated by MINPV. If this is done, there may be cells in the model with a pore volume greater than MINPV but a thickness less than the pinchout threshold. These cells will not be deactivated by the PINCH keyword.
- 166. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 166 of 499 08/04/99 NNC Generation at Local Grid Refinements Figure 54: LGR NNC generation • ECLIPSE automatically generates a form of NNC between the global host cells and the refined cells of an LGR within. • The subject is discussed in depth in other courses provided by GEOQUEST. Local Grid Refinement (LGR) Global grid cells Global/LGR cell "NNCs" as displayed by Graf
- 167. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 167 of 499 08/04/99 NNC Generation at Local Grid Refinements Cells belonging to Local Grid Refinements (LGRs) use I, J and K indices local to each LGR. The LGR cells will rarely have indices neighbouring the adjacent global cells. In simulations involving LGRs, ECLIPSE reports NNCs between LGR cells and the adjacent global grid cells. This is not strictly an NNC; it is rather a reporting convenience, because LGRs are solved separately from the global grid and there is no flow as such directly between the LGR and global grid. The user cannot alter such NNCs. The treatment of LGRs is very similar to the ECLIPSE 200 FLUX BOUNDARY OPTION; both topics are examined in greater detail in other courses offered by GEOQUEST.
- 168. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 168 of 499 08/04/99 NNCs in Dual Porosity Models Figure 55: NNC generation in dual porosity models • ECLIPSE doubles the number of layers in a dual porosity model • The upper half are matrix cells, the lower half are fracture cells • Matrix and corresponding fracture cells are automatically connected by NNCs. • The subject is discussed in more detail in other courses offered by GEOQUEST. User defines the upper NZ layers. These are treated as matrix cells Eclipse copies NZ upper layers to another NZ layers below. These are treated as fracture cells Matrix/ Fracture NNCs generated by Eclipse K I or J
- 169. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 169 of 499 08/04/99 NNCs in Dual Porosity Models Dual porosity and dual permeability reservoirs are simulated in ECLIPSE by modelling the matrix and fractures as separate groups of cells joined by automatically generated NNCs. The user in general creates the reservoir grid as normal but allocates twice as many layers as required in the RUNPSEC section. The DPGRID keyword is used later to instruct ECLIPSE to double the number of layers in the model and copy the properties of the extra layers from the existing layers. The upper layers are treated as matrix cells and the lower layers as fractures. The user must supply the fracture cell properties, matrix- fracture coupling coefficients and saturation functions for the fracture as well as the matrix cells. In dual porosity models there is no flow between matrix cells, so well completions must be moved to the lower half of the model. In dual permeability models, matrix-matrix flow is significant and completions need to be defined in the fractures in addition to the completions in the matrix cells.
- 170. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 170 of 499 08/04/99 NNC Generation in Aquifers Figure 56: Aquifer non-neighbour connections • Analytical, numeric and flux aquifers are joined to the reservoir by NNCs • The locations of these NNCs must be defined explicitly. • The NNC transmissibility may be modified • The topic is discussed in more detail in the section titled Aquifer in this course Aquifer cells Oil zone Inactive cells NNCs
- 171. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 171 of 499 08/04/99 NNC Generation in Aquifers Analytical and numeric aquifers are the most commonly used aquifer modelling facilities. A numeric aquifer is a number of cells nominated by hand to act as an aquifer. The cell properties are overwritten by the user and the NNCs between the aquifer and main body of the reservoir are specified explicitly.
- 172. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 172 of 499 08/04/99 NNC Generation in Radial Models Figure 57: Completing the circle in a radial model • Cells having boundaries at θ = 0° and 360° are not neighbours • To create an NNC here requires NNCs to be enabled and "completing the circle" 1, 4, 1 1, 1, 1 1,2,11, 3, 1 2, 2, 12, 3, 1 2, 1, 12, 4, 1 3, 2, 13, 3, 1 3, 1, 13, 4, 1 NNCs generated between θ=0 and 360 using COORDSYS --K1 K2 Complete? 1 1 COMP / /
- 173. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 173 of 499 08/04/99 NNC Generation in Radial Models In general, flow in the vicinity of a well is not exclusively in the direction radial to the wellbore. To permit a complete circumferential flow component, NNCs must be created between the cells having faces at 0° and 360°. This applies to block-centred and corner- point radial models. NNC generation between these cells is enabled by the COORDSYS keyword. To complete the circle in the upper four layers of a model having six layers use COORDSYS --K1 K2 Complete? 1 4 COMP / 5 6 INCOMP / / If the NONNC keyword has been used in RUNSPEC this will be prohibited.
- 174. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 174 of 499 08/04/99 Radial Models Figure 58: Radial model geometry • To enable radial runs, use the RADIAL keyword in RUNSPEC. • The I,J,K values then refer to the radial, azimuthal and z directions • Azimuthal distances are measured clockwise in degrees in all unit systems • Inner radius INRAD must be specified • The number of cells in the radial direction is read from NR in RUNSPEC • Radial cell dimensions are either set using DR (or DRV) or calculated by ECLIPSE if the outer radius (OUTRAD) is defined. • Azimuthal and vertical dimensions are set using DTHETA (or DTHETAV) and DZ. • The format of printed reports in the PRT file does not change. 1, 4, 1 1, 1, 1 1,2,11, 3, 1 2, 2, 12, 3, 1 2, 1, 12, 4, 1 3, 2, 13, 3, 1 3, 1, 13, 4, 12*INRAD 2*OUTRAD NR Cells in the radial direction
- 175. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 175 of 499 08/04/99 Radial Models Model geometry is Cartesian by default. To create a radial model use the RADIAL keyword in the RUNPSEC section. The model extents referred to in the DIMENS keyword are then interpreted as numbers of cells in the radial, azimuthal and vertical directions (NR, NTHETA and NZ) instead of NX, NY and NZ. Many of the keywords used to specify radial geometry and grid cell properties are different from their Cartesian versions. In general X is changed to R, Y to THETA and Z remains unaltered. The following table summarises the differences between radial and Cartesian geometries: BC Cartesian BC Radial CP Cartesian CP Radial NX, NY, NZ NR, NTHETA, NZ NX, NY, NZ NR, NTHETA, NZ DX, DY, DZ DR, DTHETA, DZ COORD, ZCORN COORD, ZCORN DXZ, DYV, DZ DRV, DTHEATAV,DZ COORD, ZCORN COORD, ZCORN PERMX, PERMY, PERMZ PERMR, PERMTHT, PERMZ PERMX, PERMY, PERMZ PERMR, PERMTHT, PERMZ PORO PORO PORO PORO MULTX(-), MULTY(-), MULTZ(-) MULTR(-), MULTTHT(-), MULTZ(-) MULTX(-), MULTY(-), MULTZ(-) MULTR(-), MULTTHT(-), MULTZ(-) TRANX, TRANY, TRANZ TRANR, TRANTHT, TRANZ TRANX, TRANY, TRANZ TRANR, TRANTHT, TRANZ Radial models will usually be centred on a well. The void at the centre of the diagram in Figure 58 of radius INRAD is intended to accommodate this. INRAD must be used to specify the inner radius of a radial model. This is to ensure that the well does not occupy some of the connecting grid cell and that all of the pore volume on the near wellbore region is accounted for, although only a warning is generated if INRAD is not the same as the well radius. Radial model geometry is defined in one of three ways; the third is most common. Default intermediate radii The outer radius can be set using OUTRAD. In this case the number of cells between INRAD and OUTRAD is NR, specified in RUNPSEC and their radii follow a logarithmic distribution based on )1(1 1 1 − − + = NR NR ii RU R RR
- 176. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 176 of 499 08/04/99 EQ. 31 where Ri+1 is the radius of the i+1th cell RI is the radius of the ith cell RNR-1 is the inner radius of the outermost block RU is the last radius defined by the user NR is the number of cells in the radial direction User-defined intermediate radii The outer radius can be set using OUTRAD. The intermediate cell radii can be set using DR or DRV, together with INRAD. Incomplete user-defined radii The default intermediate radii calculated by ECLIPSE follow a logarithmic progression which may lead to extremely small cell dimensions in the near-wellbore region. This can cause computational difficulties (see the section titled Convergence p.467). It is common practice to overwrite the default radii close to the well with user-defined values defined in the DR or DRV keyword.
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- 178. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 178 of 499 08/04/99 Output Control Figure 59: Grid Section Output Control • GRIDFILE controls grid geometry file output • The .GRID file contains only the reservoir geometry in coded form. It is binary by default. • NOGGF suppresses grid geometry file output • INIT controls initial file output • RPTGRID controls data written to the print and log files • BOUNDARY defines a box to restrict the number of cells whose data is written to the print and log files .GRID or .FGRID file Simulation grid geometry output using GRIDFILE Suppress using NOGGF .INIT or .FINIT file Static reservoir properties & characterisitics using INIT .PRT and .LOG file Printed output using RPTGRID Confine to box using BOUNDARY
- 179. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 179 of 499 08/04/99 Output Control GRIDFILE By default ECLIPSE outputs a .GRID file containing the geometrical descriptions of active cells only. To include the geometry of all cells use GRIDFILE 2 / The .GRID file contains only the geometry of the reservoir in coded form and is binary by default. NOGGF This is used to suppress .GRID file output altogether INIT This requests output of a .INIT file which contains the static reservoir properties. This includes: • All quantities defined in the GRID section that have one value per cell such as porosity, the three permeabilities, net to gross, dell centre depth, transmissibilities and transmissibility multipliers. • Saturation functions (capillary pressure and relative permeability) • PVT table data • Subdivisions of the reservoir as defined in The REGIONS Section. • Flux regions • NNC information for NNC plots in GRAF. The INIT keyword has no parameters. The .INIT file is not output by default. This file is in coded form and is binary by default. Post- processors such as GRAF use it. RPTGRID ECLIPSE can be instructed to output printed reports of simulation grid characteristics to the PRT file using the RPTGRID keyword. The keyword is followed by a number of arguments, of which there are approximately fifty in total. Unlike most other keywords, the arguments must each be in quotes. For instance RPTGRID ’PORV’ ’TRANX’ ’PERMZ’ ’ACTNUM’ /
- 180. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 180 of 499 08/04/99 will produce a report in the PRT file of the cell pore volume, X direction transmissibility, Z direction permeability and active cell number. A full list of the arguments taken by RPTGRID can be found in the ECLIPSE 100 REFERENCE MANUAL. BOUNDARY Printed output from the GRID section can be quite voluminous. If the user is only interested in a certain portion of the grid, BOUNDARY can be used to restrict the output of RPTGRID to a nominated box of cells. For instance, BOUNDARY --I1 I2 J1 J2 K1 K2 1 10 1 5 1 10 / will restrict the output to the chosen box.
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- 182. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 182 of 499 08/04/99 Grid Section Keyword Summary Figure 60: Grid section keyword summary • Cartesian Geometry • Radial Geometry • Cell Properties • Pinchouts & Deactivation • Transmissibility • Transmissibility modification • Faults • Numerical Aquifers • Operators • Dual Porosity / Permeability • Flux Boundary Option • Thermal Option • Vertical Equilibrium Option • Miscellaneous and Output Cartesian Geometry Keywords Radial Geometry Keywords Grid Cell Property Keywords for all Geometries Pinchout Control and Automatic Cell Deactivation Keywords Transmissibility Keywords Transmissibility assignment and modification keywords Fault Keywords Numerical Aquifer Keywords Operators Dual Porosity / Permeability Keywords Flux Boundary Option Keywords Thermal Option Keywords Vertical Equilibrium Option Keywords Miscellaneous and Output Control Keywords
- 183. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 183 of 499 08/04/99 Grid Section Keyword Summary Cartesian Geometry DX, DY, DZ Block centred cell dimensions DXV, DYV Block-centred vector form cell dimensions TOPS Block-centred depths of centres of cell upper faces DZ Block-centred thickness at cell centre COORD, ZCORN Corner point geometry specification Radial Geometry INRAD, OUTRAD Block-centred inner and outer radii DR, DTHETA Block-centred radial and azimuthal cell dimensions DRV, DTHETAV Block-centred vector form of radial and azimuthal cell dimensions TOPS Block-centred depths of centres of cell upper faces DZ Block-centred cell thickness COORD, ZCORN Corner point geometry specification COORDSYS Completing the circle in block-centred and corner point radial geometry Cell Properties PORO Cell porosity NTG Cell net-to-gross ratio DZNET Cell net thickness PERMX, PERMY, PERMZ Cartesian cell permeabilities in X, Y, Z PERMR, PERMTHT, PERMZ Radial cell permeabilities in R, θ, Z JFUNC Activate Leverett J Function for capillary pressure scaling according to K and φ ACTNUM Active cell specification
- 184. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 184 of 499 08/04/99 Pinchouts & Deactivation MINPV Minimum pore volume required for cell to remain active MINPVV Minimum pore volume required for cells in current box to remain active MULTPV Pore volume multipliers PINCH, PINCHOUT NNC generation across pinched-out layers PINCHXY Generate horizontal pinchout NNCs Transmissibility NEWTRAN Transmissibility will be calculated as for corner-point geometry OLDTRAN Transmissibility will be calculated as for block-centred geometry OLDTRANR Transmissibility will be calculated as for BETAII Transmissibility modification MULTX, MULTY, MULTZ Cartesian geometry upstream transmissibility multipliers MULTX-, MULTY-, MULTZ- Cartesian geometry downstream transmissibility multipliers MULTR, MULTTHT, MULTZ Radial geometry upstream transmissibility multipliers MULTR-, MULTTHT-, MULTZ- Radial geometry downstream transmissibility multipliers NNC Cartesian or radial NNC transmissibility modification Faults FAULTS Fault definition MULTFLT Transmissibility modification across faults THPRESFT Set fault threshold pressure
- 185. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 185 of 499 08/04/99 Diffusivity DIFFMX, DIFFMY, DIFFMZ Cartesian upstream diffusivity multipliers DIFFMX-, DIFFMY-, DIFFMZ- Cartesian downstream diffusivity multipliers DIFFMR, DIFFMTHT, DIFFMZ Radial upstream diffusivity multipliers DIFFMR-, DIFFMTHT-, DIFFMZ- Radial downstream diffusivity multipliers DIFFMMF Matrix-fracture diffusivity multipliers MULTFLT Multipliers for diffusivity and transmissibility across faults Numerical Aquifers AQUNUM Numerical aquifer definition AQUCON Connection of numerical aquifer to reservoir Operators ADD Add specified value to the array in the current box MULTIPLY Multiply array in current box by specified value COPY Copy data in current box between arrays COPYBOX Copy an array from one box to another of the same dimensions EQUALS Set specified arrays to constant value Dual Porosity / Permeability DPGRID Copy matrix cell data to fracture cells NODPPM Treat given fracture permeabilities as effective fracture permeabilities DZMTRX, DZMTRXV Matrix cell stack height, vector form LINKPERM Assigns grid cell permeabilities to cell faces (linking permeabilities) DPNUM Nominate cells as dual porosity as opposed to the default single porosity SIGMA, SIGMAV Matrix-fracture coupling coefficient, vector form
- 186. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 186 of 499 08/04/99 LX, LY, LZ Input representative block sizes for viscous displacement LTOSIGMA Calculate SIGMA from LX, LY, LZ. SIGMAGD, SIGMAGDV Matrix-fracture coupling coefficient for gravity drainage, vector form Flux Boundary Option FLUXNUM Assign cells to flux regions MULTIREG Multiply an array by a constant value in a given flux region EQUALREG Sets specified arrays to constants in a given flux region MULTIREGT Multiply transmissibilities between flux regions DUMPFLUX, USEFLUX Write, read flux file to, from disc, FLUXREG Nominate flux regions to be active in a USEFLUX run Independent Reservoir Regions ISOLNUM Identify individual reservoir regions RESVNUM Specify geometry for individual regions RPTISOL Write independent reservoir regions data to .PRT and/or .LOG file. Thermal Option THCONR Rock thermal conductivities Vertical Equilibrium Option COLLAPSE Specify cells to collapse in collapsed VE runs CRITPERM Set critical permeability to determine which cells are collapsed in collapsed VE runs VEDEBUG Debug output for cell relative permeability data. Miscellaneous and Output ADDZCORN Add a constant to depths of cell corners
- 187. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 187 of 499 08/04/99 EQLZCORN Reset cell corner depths BOUNDARY Restrict print and log file output to specified box BOX Open box ENDBOX Close box GRIDFILE Request grid geometry file output GDFILE Import a binary grid file INIT Request initial file output for GRAF and PSEUDO. IMPORT Import a binary grid file MAPAXES Import map origin for use in post-processing via output .GRID or .FGRID file. Not normally used by ECLIPSE. MAXVALUE, MINVALUE Apply an upper, lower limit to the array in the current box NOGGF Suppress grid geometry file output PERMAVE Modify adjacent cell permeability averaging method PSEUDOS Request special output for pseudo generation using PSEUDO RPTGRID Specify grid data output to print and log files SOLVDIRS Override default settings for principal directions in the linear solver SPECGRID Specify grid characteristics. Not normally used by ECLIPSE.
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- 189. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 189 of 499 08/04/99 THE EDIT SECTION
- 190. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 190 of 499 08/04/99 Purpose of the EDIT Section Figure 61: Purpose of the EDIT section • Pore volumes and transmissibilities cannot be edited until they have been calculated • The GRID section calculates pore volumes and transmissibilities • The EDIT section allows pore volume, transmissibility, cell centre depth and non- neighbour connection modification • Certain keywords that modify cell characteristics are specific to the EDIT section even though they may resemble GRID section keywords • Most GRID section keywords can also be use in the EDIT section • The EDIT section is optional • Use the GRID section to define the static reservoir properties in preference to the EDIT section if possible. GRIDSection EDITSection Pore Volumes Transmissibilities Cell Depths Pore Volumes Transmissibilities Cell Depths
- 191. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 191 of 499 08/04/99 Purpose of the EDIT Section The GRID section provides the data required to calculate pore volume, transmissibility, cell centre depths and direct and non-neighbour connections for the simulation grid. A number of consistency and integrity checks are performed by ECLIPSE during this process. When finished, but not before, the pore volumes, depths, transmissibilities and connections may be adjusted directly by the user. Thereafter, the raw data from which pore volumes and transmissibilities have been derived cannot be edited. The EDIT section is used to alter pore volumes, transmissibilities, non-neighbour connections and cell centre depths. Most of the keywords usable in the GRID section also apply to the EDIT section. Exceptions include the keywords used to enter basic data such as PORO, PERMX etc. The syntax of the EDIT section is as for the GRID section. NOTE. None of the TRAN keywords affect non-neighbour connection transmissibilities across faults. Use the EDITNNC keyword to modify non-neighbour connections by hand. If any of the MULT keywords are specified in the EDIT section they act as multipliers on the edited value. NNC transmissibilities are also affected by the MULT keywords, just as in the GRID section. Use of transmissibility multipliers in the EDIT section is not recommended. Transmissibility multiplier keywords should not be applied in the EDIT section to Local Grid Refinements (LGRs)
- 192. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 192 of 499 08/04/99 Edit Section Keyword Summary Figure 62: EDIT section keyword summary • Cell centre depth assignment keywords • Cell transmissibility assignment and modification keywords • Diffusivity assignment keywords • Cell pore volume assignment and modification keywords • Operators • Miscellaneous keywords Cell centre depth assignment keywords Cell transmissibility assignment and modification keywords Diffusivity assignment keywords Cell pore volume assignment and modification keywords Operators Miscellaneous keywords
- 193. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 193 of 499 08/04/99 Edit Section Keyword Summary Keyword Function Usable in GRID Section ADD, MULTIPLY Add, multiply arrays in the current box by a set value á BOUNDARY Restrict PRT file output to specific box á BOX, ENDBOX Open, close box of cells for property definition or modification á COPY Copy data form one array to another within the current box á DEPTH Set cell centre depth Χ DIFFX, DIFFY, DIFFZ Cartesian geometry diffusivities Χ DIFFR, DIFFTHT, DIFFZ Radial geometry diffusivities Χ EDITNNC Non-neighbour connection modification á EQUALS Set constant array value in the current box á IMPORT Import binary grid data á MAXVALUE, MINVALUE Apply upper, lower limit to array values in the current box á MULTFLT Upstream fault transmissibility multiplier á MULTIPLY Multiply arrays by specified constants within given box á MULTPV Set cell pore volume multiplier á
- 194. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 194 of 499 08/04/99 MULTX/X-, MULTY/Y-, MULTZ/Z- Cartesian transmissibility multipliers á MULTR/R-, MULTTHT/THT-, MULTZ/Z- Radial transmissibility multipliers á PORV Set cell pore volume Χ TRANX, TRANY, TRANZ Cartesian geometry transmissibility assignment Χ TRANR, TRANTHT, TRANZ Radial geometry transmissibility assignment Χ
- 195. THE PROPS SECTION– FLUID PROPERTIES
- 196. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 196 of 499 08/04/99 Purpose of Fluid Properties Figure 63: Purpose of fluid property data • This section is restricted to fluid PVT properties and rock compressibility • The data is needed to evaluate phase density at reservoir and stock tank conditions using the black oil equation of state • Data must be supplied to evaluate the PVT properties of all the fluids at any time • These are formation volume factor, viscosity, GOR and / or OGR • PVT characteristics at reference (surface) conditions must be supplied • Initial GORs and/or OGRs may also be specified. • There may be more than one set of tables if the fluid properties vary within the reservoir • Saturation functions in general and relative permeability and endpoint scaling in particular are discussed in another section of the ECLIPSE 100 USER COURSE. 1st stage separator 2nd stage separator Stock tank gasStock tank oil Vapour Liquid Reservoir conditions
- 197. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 197 of 499 08/04/99 Purpose of Fluid Properties ECLIPSE performs material balance calculations at each step of the simulation. To this, the density of each phase must be calculated. Since the density of each phase depends on pressure and the quantities of additional dissolved components in each phase, the phase PVT properties are the ideal means of specifying these fluid characteristics. Ultimately they are derived from a combination of laboratory experiments and field tests. This type of data requires a set of reference conditions, which are the surface densities of each component. NOTE that ECLIPSE is an isothermal simulator; temperature dependence is not taken into account explicitly and it is assumed that all component parts of the simulation are at a constant temperature.
- 198. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 198 of 499 08/04/99 Black Oil Overview Figure 64: Generalised two-phase PVT envelope • Strictly, black oils contain no dissolved gas at surface conditions. • Black oil simulators operate best in the single phase regions far from the critical point (Pc, Tc). • Crossing into the two-phase region involves change of composition • Black oil simulators cannot model compositional variations directly because fluid properties depend only on pressure in the black oil approximation • Varying gas/oil and oil/gas ratios are used to approximate small compositional variation in the two-phase region • The approximation breaks down if compositional changes are large • The compulsory PROPS section is where the fluid PVT data is specified • PVT data at standard conditions (reference data) must also be specified in the PROPS section • The minimum requirements depend on the phases and components present P T Bubble point curve: 100% liquid Pc , Tc 25%liquid 50% liquid Dew pointcurve:100% vapour A - liquid B - vapour 75% liquid DD BB AA EE FF HH CC GG
- 199. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 199 of 499 08/04/99 Black Oil Overview The various regions in Figure 64 are the different parts that make up a typical phase envelope. The lines AA-HH represent paths that oil and / or gas may take during production. At pressures and temperatures to the left of the critical point (Pc, Tc) the line bounding the phase envelope is the bubble point line; on the right it is named the dew point line. Region A represents what is often termed black oil, which may cross the bubble point line and is distant from the critical point. Its boundaries are not distinct. The oil phase may, and usually does, contain a dissolved gas component. The strict definition of a black oil is in fact oil which contains no dissolved gas at stock tank conditions. Line AA represents oil above the bubble point. The pressure is decreased isothermally within the reservoir and the fluid viscosity and compressibility may change but it remains single phase. The dissolved gas concentration does not change. Free gas is, however, produced since the gas is taken to come out of solution at the well head. In ECLIPSE terminology this is known as dead oil. Line BB represents black oil initially above the bubble point. As the pressure is dropped only the oil viscosity and compressibility may change above the bubble point. The GOR is fixed. The composition remains the same until the bubble point is reached, when gas begins to come out of solution. If this happens within the reservoir, a gas cap may form. If it happens in a well bore free gas is produced at the wellhead. In either case as the pressure drops isothermally along line BB the path the fluids take crosses quality lines inside the phase envelope and more gas comes out of solution. The GOR of produced oil is considerably lower than that of reservoir oil. In ECLIPSE terminology this is known as live oil. Line CC represents a two-phase mixture. Above the GOC the pressure is below the bubble point and gas exists as a free gas phase (gas cap). Below the gas-oil contact the pressure is above the bubble point; the oil phase contains a dissolved gas component. As the pressure is further decreased isothermally along line CC the mixture crosses quality lines inside the phase envelope and more gas comes out of solution. In ECLIPSE terminology this is live oil. Line DD represents an initially near-critical fluid. Above and close to the critical point it is difficult to tell whether the fluid is a liquid or a vapour. As the fluid passes through the critical point at (Pc, Tc) along line DD it will become a two-phase mixture but the
- 200. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 200 of 499 08/04/99 transition will not be easily seen. At a suitable combination of reservoir pressure and BHP a single phase may flow into the well while the transition to two phases takes place within the wellbore. Line EE represents an initially single-phase vapour. This vapour contains a vaporised oil component but as the pressure is lowered along EE it cannot reach the dew point as it is beyond the phase envelope. In ECLIPSE terminology this is a dry gas. Line FF is also a two-phase mixture initially within the phase envelope. As the pressure is dropped along FF the liquid phase gradually evaporates until the dew point line is crossed, when no liquid remains. In ECLIPSE terminology the vapour is a wet gas. Line GG represents a volatile oil initially above the dew point. As the pressure is lowered the liquid phase condenses out. This counter-intuitive behaviour is known as retrograde condensation and takes place in condensate reservoirs blown down below the dew point. In ECLIPSE this is also known as a wet gas. Line HH represents oil which progresses in an adiabatic transition from a single oil phase to a two-phase oil-gas mixture. This might occur in a separator. The reservoir fluids are taken to be at fixed temperatures in the reservoir, separator and at surface conditions, although each may be different. For instance, the temperature at standard conditions is usually different from the reservoir temperature. In such situations the oil PVT data can be represented as tables of properties as functions of pressure only, at a specific temperature. ECLIPSE and other black oil simulators are best suited to model the behaviour of this type of reservoir fluid Single-phase systems containing only vapour, such as in the region of point B, are also well suited to simulation using ECLIPSE. As with black oil, the fluid is far from the critical point and does not cross the dew point line so the vaporised oil concentration (if any) remains fixed. In ECLIPSE terminology this is known as a dry gas. Black oil simulators such as ECLIPSE cannot model compositional changes explicitly. If processes such as liberation of gas or condensate dropout need to be modelled, it has to be done indirectly by allowing the solution GOR (Rs) and vapour OGR (Rv) to vary. Fluids having these characteristics are referred to as live oils and wet gases, respectively To ensure that the fluids can still be modelled sufficiently accurately using a black oil approach: • The amount of condensate dropout or gas liberation should be a small part of the hydrocarbon in place
- 201. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 201 of 499 08/04/99 • The remaining hydrocarbon composition should not change significantly when gas is liberated or condensate drops out • The path taken by the fluids should be far from the critical point • The process should be isothermal If this cannot be done, a fully compositional approach must be taken.
- 202. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 202 of 499 08/04/99 Black oil versus compositional simulation Figure 65: Steps taken in black oil and compositional simulations • Black oil simulators spend most of their CPU time solving flow equations. PVT is evaluated by table lookup • Compositional simulators have the extra burden of iterative EoS solution and flash calculations • Compositional simulation is almost always more CPU intensive than black oil simulation • This course deals exclusively with black oil simulation. Compositional simulation is discussed in other training courses offered by GEOQUEST. Flow equation solution for each cell subject to material balance Black Oil PVT data lookup from supplied tables Compositional Flow equation solution for each cell subject to material balance Iterative solution of cubic equation of state for each component in each cell Iterative flash of component mixture to equilibrium conditions for each cell For every timestep
- 203. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 203 of 499 08/04/99 Black oil versus compositional simulation Black oil models are appropriate in cases where compositional changes are insignificant and the fluid is far from the fluid critical point. Then, the fluid properties are comparatively stable and can be represented by a set of tables of PVT properties as functions of pressure. The computational overhead in calculation of PVT properties by table lookup is very small. The bulk of the CPU time of a black oil simulation is spent in solving the coupled system of flow equations for each cell, plus well injection and production, whilst ensuring that material balance is preserved. Compositional simulation is required when the black oil approximation breaks down. Compositional simulators such as ECLIPSE 300 perform the same fluid flow calculations as a black oil simulator but are subject to additional computational burdens. The reservoir fluid is described in terms of a number of flowing pseudocomponents, generally around half a dozen. Each pseudocomponent represents a group of individual hydrocarbon components. Once the fluid flows have been calculated each pseudocomponent must be flashed to equilibrium conditions. This is an iterative process. Then a cubic equation of state (EoS) must be solved for each pseudocomponent. Again, this is an iterative process. Both the flash calculations and EoS solution are performed at each timestep in every grid cell. In practice the flow calculations often demand less than 50% of the CPU time of a compositional simulation; flash calculations and EoS solution take up the remainder.
- 204. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 204 of 499 08/04/99 The Oil Equation of State Figure 66: Oil equation of state for the black oil model • All quantities depend only on pressure • (s) refers to surface conditions, (r) to reservoir conditions • The dissolved gas component Vg (r) is contained in the oil phase • The equation is not solved, it is entered as tables which are interpolated and extrapolated • For a dead oil Rs is fixed and pressure is always above bubble point • For a live oil Rs has to be supplied at pressures below the bubble point )( )( )( )()( )()( )( and where s s s rr ss r o g s o go o o gso o V V R V VV B B R = + = + = ρρ ρ
- 205. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 205 of 499 08/04/99 The Oil Equation of State The black oil equation of state (EoS) treats oil as a single phase whose properties depend only on pressure. Black oil in terms of PVT is far from the critical point. The composition of black oil is treated as fixed; other properties such as density and viscosity can be described relatively easily because their behaviour far from the critical point is not complex. Black oil is taken to be at a fixed temperature and the reservoir, well and surface temperatures are each taken to be constant. In such situations the oil PVT data can be represented as tables of properties as functions of pressure only. In practice the black oil model is often usable below the bubble point. Live oil in ECLIPSE terminology is oil that may fall below the bubble point whereas dead oil may not. If a reservoir to the left of the critical point in Figure 64 has a gas cap then the bubble point is at the gas-oil contact. The pressure above the GOC, in the gas phase, must be less than the bubble point. Live and dead oils alike contain a gas component dissolved in the oil phase. This distinction between phases and components is central to understanding the black oil model. The purpose of the term containing Rs in the black oil equation of state is to describe the effect of the dissolved gas component on the oil phase properties. For a dead oil this is fixed; for live oil Rs may vary. NOTE that dead oil reservoirs produce free gas. It does not come out of solution in the reservoir but the dissolved gas component may be liberated at any other location where the pressure is lower than the bubble point pressure e.g. in a wellbore or at surface conditions. If the reservoir contains only dead oil of one GOR and bubble point, a single value of Rs can be specified at the oil bubble point using RSCONST. If, on the other hand, a number of dead oils are fully separated (e.g. by fault blocks or stratigraphic traps), oils of different GOR and bubble point can be assigned to different parts of the reservoir using the PVTNUM keyword together with one set of PVT tables for each oil. The RSCONSTT keyword should then be used to specify the bubble point GOR for the oil in each PVT region. A black oil model can be used to model live oil provided several conditions are met to an acceptable degree i.e. the PVT model is fit for the intended purpose: • The oil composition does not change when gas comes out of solution. Ideally this means that the distribution of hydrocarbon molecular weights (or fingerprint) is the
- 206. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 206 of 499 08/04/99 same for oil and gas. Since this is impossible, the engineer has to be satisfied that the oil properties do not change significantly when gas comes out of solution. • The amount of gas coming out of solution is a small proportion of the hydrocarbon in place. Since evolved gas is bound to alter the composition of remaining oil, this is really a consequence of the above condition. • Evolution of gas does not bring the mixture too close to the critical point. Such oils are often termed grey oils but are known as live oils in ECLIPSE terms. Their compositional variation cannot be modelled directly using ECLIPSE or any other black oil model. Instead, the solution gas-oil ratio Rs is used to mimic the effect of compositional variations when gas comes out of solution or is dissolved. To do this, Rs must vary and in live oil models, Rs is tabulated versus pressure. In live oil models the initial Rs is specified at the GOC when the model is initialised and as a function of depth using either RSVD or PBVD. Black oil modelling of gases is very similar. Dry gas is analogous to dead oil in ECLIPSE terminology. Dry gas may contain a vaporised oil component described by the oil-gas ratio Rv.
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- 208. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 208 of 499 08/04/99 Dead Oil PVT Data Entry Using PVDO Figure 67: Dead oil PVT data entry using PVDO • The PVDO keyword is used to specify properties of oil above the bubble point (undersaturated oil) • It is a table of formation volume factor and viscosity versus pressure • Multiple PVDO tables may follow a single PVDO keyword if there are distinct dead oils in the reservoir • PVDO tables are attached to specific cells or groups of cells. • The simulation is terminated if the pressure in any grid cell falls below the bubble point for that cell. P Pb Bo µo Rs PVDO --Undersaturated oil --Pressure Bo µo 2500 1.260 0.5 3000 1.257 1* 3500 1.254 0.6 4000 1.251 1* 4500 1.248 1* / RSCONST --GOR Pb 0.656 2500 /
- 209. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 209 of 499 08/04/99 Dead Oil PVT Data Entry Using PVDO The keyword format is columns of pressure, oil formation volume factor and viscosity in that order from left to right. Defaulted entries will be interpolated by ECLIPSE, although pressure values cannot be defaulted. A single forward slash terminates the table Pressure values should increase monotonically down the table. Formation volume factors should decrease monotonically with increasing pressure. ECLIPSE outputs warnings or error messages if this is not the case. NOTE that a single default value must be entered as 1*, not a blank space. If this is not done ECLIPSE simply interprets the next number read as a data value. If errors or warning messages do not result, incorrect simulation results are certain and convergence problems highly likely. For instance, if the first 1* entry in Figure 67 were omitted, the oil viscosity at 3000 psia would be read as 3500 cP. Since the reservoir pressure cannot drop below the bubble point, there is no point in including data below Pb and the lowest pressure in the table should be the bubble point pressure. If the pressure in any cell reaches the bubble point for that cell, the simulation will terminate. The oil phase contains a fixed quantity of dissolved gas component. This is specified using RSCONST. If more than one oil is present, RSCONSTT is used to specify the bubble point GOR for each oil. Note that the FIELD units of RSCONST and RSCONSTT are Mscf/stb where M denotes 1000.
- 210. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 210 of 499 08/04/99 Dead Oil PVT Data Entry Using PVCDO Figure 68: Dead oil PVT data entry using PVCDO • The PVCDO keyword is used to specify properties of oil above the bubble point (undersaturated oil) • Instead of specifying Bo and µo versus pressure, effectively the slopes of Bo and µo are specified at the bubble point • A maximum pressure has to be specified using PMAX • Multiple PVCDO tables may follow a single PVCDO keyword if there are distinct dead oils in the reservoir • PVCDO tables are attached to specific cells or groups of cells. • The simulation is terminated if the pressure in any grid cell falls below the bubble point for that cell. PVCDO --Undersaturated oil --P Bo Co µo Coµ 2500 1.260 6E-6 0.5 1E-6 / RSCONST --GOR Pb 0.656 2500 / PMAX 4500 / P Pb Rs DP DBo DP Dµo
- 211. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 211 of 499 08/04/99 Dead Oil PVT Data Entry Using PVCDO The keyword format is a single line of pressure, oil formation volume factor, compressibility, viscosity and viscosibility in that order from left to right. A single forward slash terminates the table. The compressibility is defined as −= dP dV V C o o o 1 EQ. 32 Or −= dP dB B C o o o 1 EQ. 33 Where the viscosibility is = dP d C o o o µ µ µ 1 EQ. 34 Instead of defining the curves of Bo and µo versus pressure, the values and slopes at the bubble point are supplied. This alternative to PVDO is suitable if the undersaturated curves are straight lines. In principle, ECLIPSE may extrapolate to any pressure above the bubble point. To prevent this the PMAX keyword must be entered. If the pressure in any cell reaches the bubble point for that cell, the simulation will terminate. The oil phase contains a fixed quantity of dissolved gas component. This is specified using RSCONST. If more than one oil is present, RSCONSTT is used to specify the bubble point GOR for each oil. Note that the FIELD units of RSCONST and RSCONSTT are Mscf/stb where M denotes 1000.
- 212. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 212 of 499 08/04/99 Live Oil PVT Data Entry Using PVTO Figure 69: Live oil PVT data entry with PVTO • The PVTO keyword is used to specify properties of oil above (undersaturated) and below (saturated) the bubble point • It is a table of pressure, formation volume factor and viscosity versus bubble point gas/oil ratio • The undersaturated FVF and viscosity must be specified at the highest pressure in the table • Multiple PVTO tables may follow a single PVTO keyword if there are distinct dead oils in the reservoir • PVTO tables are attached to specific cells or groups of cells. Pb at Rs=0.77 Pb at Rs=0.241 Bo µo PVTO --Rs Pb Bo µo 0.13700 1214.70 1.17200 1.97000 / 0.19500 1414.70 1.20000 1.55600 / 0.24100 1614.70 1.22100 1.39700 / 0.28800 1814.70 1.24200 1.28000 / 0.37500 2214.70 1.27800 1.09500 / 0.46500 2614.70 1.32000 0.96700 / 0.55800 3014.70 1.36000 0.84800 / 0.66100 3414.70 1.40200 0.76200 / 0.77000 3814.70 1.44700 0.69100 / 4214.70 1.44050 0.69400 / 4614.70 1.43400 0.69700 / /
- 213. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 213 of 499 08/04/99 Live Oil PVT Data Entry Using PVTO The keyword format in the saturated region is columns of GOR at the saturation pressure, saturation pressure, oil formation volume factor and viscosity in that order from left to right. In the undersaturated region the Rs values are omitted since the GOR is fixed above the saturation pressure. Defaulted entries will be interpolated by ECLIPSE, although Rs values cannot be defaulted. A single forward slash terminates the table Note that a single default value must be entered as 1*, not a blank space. If this is not done ECLIPSE simply interprets the next number read as a data value. For instance, if the 1* entries in Figure 67 were omitted, the oil viscosity at 3814.7 would be read as 4214.70 cP. The reservoir pressure may drop below the bubble point and the datum pressure is not necessarily above the highest bubble point pressure. Suppose the pressure in a gas/oil/water reservoir at the GOC is 3814.7, the highest bubble point pressure in the PVTO table, prior to blowdown. Oil PVT data at pressures up to highest pressure in the aquifer are required because ECLIPSE calculates Rs in every cell for reasons of computational stability. The converse applies to the gas cap. During blowdown the pressure at the GOC drops below the saturation pressure and gas is liberated. The oil Rs drops, following the saturated curve. If the reservoir is re- pressurised, cells at (say) 2614.7 containing free gas will reabsorb the liberated gas, following the saturated Rs vs. Pb curve. If by then the gas has migrated upwards and none is left to be reabsorbed, ECLIPSE interpolates an undersaturated curve at an Rs of 0.465 between the other undersaturated curves at Rs=0.241 and 0.77. NOTE. ECLIPSE stores PVT tables internally as 1/B and 1/(Bµ); these quantities are interpolated. At high pressures, Bµ is quite small so small inaccuracies in the reciprocal can lead to large variations in the FVF values. If insufficient PVT data is supplied, ECLIPSE may extrapolate the PVT table data to inaccurate or non-physical values.
- 214. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 214 of 499 08/04/99 Live Oil PVT Data Entry Using PVCO Figure 70: Live oil PVT data entry with PVCO • The PVCO keyword is used to specify properties of oil above (undersaturated) and below (saturated) the bubble point • Instead of specifying Bo and µo versus pressure, the slopes of Bo and µo are specified at the bubble point • Multiple PVCO tables may follow a single PVCO keyword if there are distinct live oils in the reservoir • PVCO tables are attached to specific cells or groups of cells. Pb @ Rs=0.375 Pb @ Rs=0.375 Bo µo PMAX 6000 / PVCO --Pb Rs Bo Vo Co Coµ 1214.70 0.13700 1.17200 1.97000 1E-5 0 1414.70 0.19500 1.20000 1.55600 1* 0 1614.70 0.24100 1.22100 1.39700 1* 0 1814.70 0.28800 1.24200 1.28000 1* 0 2214.70 0.37500 1.27800 1.09500 1* 0 2614.70 0.46500 1.32000 0.96700 1* 0 3014.70 0.55800 1.36000 0.84800 1* 0 3414.70 0.66100 1.40200 0.76200 1* 0 3814.70 0.77000 1.44700 0.69100 1* 0 /
- 215. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 215 of 499 08/04/99 Live Oil PVT Data Entry Using PVCO The keyword format in the saturated region is columns of bubble point pressure, GOR at the bubble point pressure, oil formation volume factor, viscosity, compressibility and viscosibility in that order from left to right. It is the live oil equivalent of PVCDO. The given data points specify the properties at a series of saturation pressures and the differential quantities are used to extrapolate into the undersaturated region. A single forward slash terminates the table NOTE that a single default value must be entered as 1*, not a blank space. If this is not done ECLIPSE simply interprets the next number read as a data value. For instance, if the first 1* entry in Figure 70 were omitted, the oil viscosibility at 1414.7 would be read as zero.
- 216. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 216 of 499 08/04/99 The Gas Equation of State Figure 71: Gas equation of state for the black oil model • All quantities depend only on pressure • (s) refers to surface conditions, (r) to reservoir conditions • The vaporised oil component Vo (r) is contained in the gas phase • The equation is not solved, it is entered as tables which are interpolated and extrapolated • For a dry gas Rv is fixed and pressure is always below dew point • For a wet gas Rv must be supplied at pressures above the dew point )( )( )( )()( )()( )( and where s s s rr ss r g o v g og g g ovg g V V R V VV B B R = + = + = ρρ ρ
- 217. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 217 of 499 08/04/99 The Gas Equation of State The black oil equation of state (EoS) for gas treats gas as a single phase whose properties depend only on pressure. Strictly, gas in the black oil model in terms of PVT is far from the critical point. The composition of gas is treated as fixed; other properties such as density and viscosity can be described relatively easily because their behaviour far from the critical point is not complex. The gas is also taken to be at a fixed temperature – the reservoir, well and surface temperatures are all taken to be constant. In such situations the gas PVT data can be represented as tables of properties as functions of pressure only. In practice the black oil model for gas is often usable in the two-phase region. A wet gas in ECLIPSE terminology is a gas that may cross the dew point curve. If a reservoir to the right of the critical point in Figure 64 has a gas cap then the dew point is at the gas-oil contact. The pressure above the GOC, in the gas phase, must be less than the dew point and greater than the dew point below the GOC. Wet and dry gases alike contain an oil component vaporised in the gas phase. This distinction between phases and components is central to understanding the black oil model. The purpose of the term containing Rv in the gas equation of state is to describe the vaporised oil component in the gas phase. For a dry gas this is fixed; for a wet gas Rv may vary. NOTE that dry gas reservoirs produce oil. It does not condense in the reservoir or wellbore but the vaporised oil component is liberated at surface conditions. If the reservoir contains only dry gas of one OGR and dew point, a single value of Rv can be specified at the gas dew point using RVCONST. If, on the other hand, a number of dry gases are fully separated (e.g. by fault blocks or stratigraphic traps), gases of different OGR and dew point can be assigned to different parts of the reservoir using the PVTNUM keyword together with one set of PVT tables for each gas. The RVCONSTT keyword should then be used to specify the dew point OGR for the gas in each PVT region. A black oil model can be used to model wet gas provided several conditions are met to a acceptable degree: • The gas composition does not change when oil condenses from the vapour phase. • The distribution of hydrocarbon molecular weights (or fingerprint) is the same for oil and gas.
- 218. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 218 of 499 08/04/99 • Since this is impossible, the engineer has to be satisfied that the gas properties do not change significantly when oil is condensed. • The amount of oil deposited from the vapour phase is a small proportion of the hydrocarbon in place. Since condensed oil is bound to alter the composition of remaining gas, this is really a consequence of the above condition. • Evolution of oil does not bring the mixture too close to the critical point. Compositional variation cannot be modelled directly using ECLIPSE or any other black oil model. Instead, the vapour oil-gas ration Rv is used to approximate the effect of compositional variations when oil is transferred to and from the vapour phase. To do this, Rv must vary and in wet gas models, Rv is tabulated versus pressure. In wet gas models the initial Rv is specified at the GOC when the model is initialised and as a function of depth using either RVVD or PDVD.
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- 220. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 220 of 499 08/04/99 Dry Gas Data entry Using PVZG Figure 72: Dry Gas Data Entry Using PVZG • The PVZG keyword is used to specify properties of gas below the dew point or well beyond the critical point • The first record is a single item specifying the reference temperature for the remaining data • The remaining records are columns of pressure, z factor and viscosity in that order • Multiple PVZG tables may follow a single PVZG keyword if there are distinct dry gases in the reservoir • PVZG tables are attached to specific cells or groups of cells. • The simulation is terminated if the pressure in any grid cell reaches the dew point line for that cell. PVZG --Reference temperature 150 / --Pressure Z Viscosity Factor 400 1.22 0.01300 1200 1.30 0.01400 2000 1.34 0.01500 2800 1.50 0.01600 3600 1.55 0.01700 4000 1.70 0.01750 4800 1.82 0.01850 5200 1.82 0.01900 /
- 221. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 221 of 499 08/04/99 Dry Gas Data entry Using PVZG The keyword format is reference pressure in the first record followed by columns of pressure, gas z factor and viscosity in that order from left to right. Defaulted entries will be interpolated by ECLIPSE, although pressure values cannot be defaulted. A single forward slash terminates the table Pressure values should increase monotonically down the table. z factors should increase monotonically with pressure. ECLIPSE outputs warnings or error messages if this is not the case. NOTE that a single default value must be entered as 1*, not a blank space. If this is not done ECLIPSE simply interprets the next number read as a data value. If errors or warning messages do not result, incorrect simulation results are certain and convergence problems highly likely. Since the reservoir pressure cannot drop below the dew point, there is no point in including data below Pd and the lowest pressure in the table should be the dew point pressure. If the pressure in any cell reaches the dew point for that cell, the simulation will terminate. The gas phase contains a fixed quantity of vaporised component. This is specified using RVCONST. If more than one gas is present, RVCONSTT is used to specify the dew point GOR for each gas. Note that the FIELD units of RVCONST and RVCONSTT are stb/Mscf where M denotes 1000.
- 222. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 222 of 499 08/04/99 Dry Gas PVT Data Entry Using PVDG Figure 73: Dry gas PVT using PVDG • The PVDG keyword is used to specify properties of gas below the dew point or well beyond the critical point • It is a table of formation volume factor and viscosity versus pressure • Multiple PVDG tables may follow a single PVDG keyword if there are distinct dry gases in the reservoir • PVDG tables are attached to specific cells or groups of cells. • The simulation is terminated if the pressure in any grid cell reaches the dew point line for that cell. • PVDG is an alternative to the PVZG keyword (see p.220) PVDG --P Bg µg 1214.70 13.9470 0.01240 1414.70 7.02800 0.01250 1614.70 4.65700 0.01280 1814.70 3.45300 0.01300 2214.70 2.24000 0.01390 2614.70 1.63800 0.01480 3014.70 1.28200 0.01610 3414.70 1.05200 0.01730 3814.70 0.89000 0.01870 / RVCONST --Rv Pd 0.0047 1100 /
- 223. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 223 of 499 08/04/99 Dry Gas PVT Data Entry Using PVDG The keyword format is columns of pressure, gas formation volume factor and viscosity in that order from left to right. Defaulted entries will be interpolated by ECLIPSE, although pressure values cannot be defaulted. A single forward slash terminates the table Pressure values should increase monotonically down the table. Formation volume factors should decrease monotonically with pressure. ECLIPSE outputs warnings or error messages if this is not the case. NOTE that a single default value must be entered as 1*, not a blank space. If this is not done ECLIPSE simply interprets the next number read as a data value. If errors or warning messages do not result, incorrect simulation results are certain and convergence problems highly likely. Since the reservoir pressure cannot drop below the dew point, there is no point in including data below Pd and the lowest pressure in the table should be the dew point pressure. If the pressure in any cell reaches the dew point for that cell, the simulation will terminate. The gas phase contains a fixed quantity of vaporised component. This is specified using RVCONST. If more than one gas is present, RVCONSTT is used to specify the dew point GOR for each gas. Note that the FIELD units of RVCONST and RVCONSTT are stb/Mscf where M denotes 1000.
- 224. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 224 of 499 08/04/99 Wet Gas PVT Data Entry Using PVTG Figure 74: Wet gas PVT data using PVTG • The PVTG keyword is used to specify properties of gas above (undersaturated) and below (saturated) the dew point • It is a table of Rv, Bg and viscosity as functions of pressure • The undersaturated Rv, Bg and µg must be specified at the highest Pg in the table. • Multiple PVTG tables may follow a single PVTG keyword if there are distinct wet gases in the reservoir • PVTG tables are attached to specific cells or groups of cells. PVTG --Pg Rv Bg µg 30 0.000132 0.04234 0.01344 0 0.04231 0.01389 / undersaturated 60 0.000124 0.02046 0.01420 0 0.02043 0.01450 / undersaturated 90 0.000126 0.01328 0.01526 0 0.01325 0.01532 / undersaturated 120 0.000135 0.00977 0.01660 0 0.00973 0.01634 / undersaturated 150 0.000149 0.00773 0.01818 0 0.00769 0.01752 / undersaturated 180 0.000163 0.006426 0.01994 0 0.006405 0.01883 / undersaturated 210 0.000191 0.005541 0.02181 0 0.005553 0.02021 / undersaturated 240 0.000225 0.004919 0.02370 0 0.004952 0.02163 / undersaturated 270 0.000272 0.004471 0.02559 0 0.004511 0.02305 / undersaturated 295 0.000354 0.004194 0.02714 0 0.004225 0.02423 / undersaturated 310 0.000403 0.004031 0.02806 0 0.004081 0.02492 / undersaturated 330 0.000469 0.003878 0.02925 0 0.003913 0.02583 / undersaturated 530 0.000479 0.003868 0.02935 0 0.003903 0.02593 / undersaturated /
- 225. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 225 of 499 08/04/99 Wet Gas PVT Data Entry Using PVTG The keyword format in the saturated region is columns of pressure, oil-gas ratio, gas formation volume factor and viscosity in that order from left to right. In the undersaturated regions the Pg values are omitted from the extra data records. Defaulted entries will be interpolated by ECLIPSE, although Pg values cannot be defaulted. A single forward slash terminates the table NOTE that a single default value must be entered as 1*, not a blank space. If this is not done ECLIPSE simply interprets the next number read as a data value. Figure 74 is a plot of formation volume factor and viscosity versus Rv. The straight lines meeting the left vertical axis represent the transition across the phase envelope at a fixed pressure. NOTE. ECLIPSE stores PVT tables internally as 1/B and 1/(Bµ); these quantities are interpolated. At high pressures, Bµ is quite small so small inaccuracies in the reciprocal can lead to large variations in the FVF values. If insufficient PVT data is supplied, ECLIPSE may extrapolate the PVT table data to inaccurate or non-physical values.
- 226. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 226 of 499 08/04/99 The Water Equation of State Figure 75: The water equation of state • All quantities depend only on pressure • (r) refers to reservoir conditions, (s) to surface conditions • The water phase has only a water component. • Oil and gas do not dissolve in water, and vice versa • One line of data is required in PVTW for every PVT region )( )( )( )( where s r s r w w w w w w V V B B = =
- 227. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 227 of 499 08/04/99 The Water Equation of State The black oil equation of state (EoS) for water treats gas as a single phase whose properties depend only on pressure. The PVT properties of water are specified using the PVTW keyword. For example PVTW --Pref Bw Cw µw Cwµ 4000 1.03 3.0E-6 040 0.0 / where Pref is a reference pressure Bw is the water formation volume factor at the reference pressure Cw is the water compressibility = dP dB B C w w w 1 EQ. 35 µw is the water viscosity at the reference pressure Cwµ is the water viscosibility = dP d C w w w µ µ µ 1 EQ. 36 ECLIPSE calculates the water formation volume factor by approximating )( )()( 0 0 PPC ePBPB w ww −− = EQ. 37 Where P0 is a reference pressure and Cw the compressibility, to − +−+≈ 2 )( )(1)()( 2 0 2 00 PPC PPCPBPB w www EQ. 38 Reservoir water may differ from region to region in which case the PVT properties have to be specified for each region using one line of data for each region in the PVTW keyword.
- 228. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 228 of 499 08/04/99 Reference Densities Figure 76: Reference densities • In the reservoir the liquid hydrocarbon phase is stock tank oil, usually with some dissolved stock tank gas • In the reservoir the vapour hydrocarbon phase is stock tank gas, perhaps with some vaporised stock tank oil • Stock tank oil and gas component characteristics are measured at the separator train • Stock tank oil and gas component densities as the separator train are specified using either DENSITY or GRAVITY. w w w g ov g o gso o B B R B R s r ss gr ss r )( )( )() )( )()( )( ρ ρ ρρ ρ ρρ ρ = + = + = Surface densities are specified using either DENSITY --Oil Water Gas --Dens Dens Dens or GRAVITY --Oil Water Gas --API Specific Specific --Gravity Gravity Gravity Vapour Liquid Reservoir conditions 1st stage separator 2nd stage separator Stock tank gas Stock tank oil
- 229. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 229 of 499 08/04/99 Reference Densities All PVT properties are functions of pressure in the black oil model. The surface densities of each component are also pressure and temperature dependent. Standard pressure and temperature are not defined in ECLIPSE; they may take whatever values prevail at stock tank conditions. The surface densities can be specified either by densities or specific gravity and oil API. For instance: GRAVITY --Oil API Water specific Gas specific --Gravity Gravity gravity 32 1.050 0.700 / or DENSITY --Oil Water Gas --Density Density Density --Kg/m3 Kg/m3 Kg/m3 865 1050 0.9051 / where 5.131 5.141 −= gravity API EQ. 39 Where gravity is the liquid specific gravity and API is in degrees. The water specific gravity is the ratio of water density to the density or pure water. The gas specific gravity is the ratio of gas density to the density of air. This and other unit conversion methods can be found in the ECLIPSE 100 TECHNICAL APPENDICES.
- 230. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 230 of 499 08/04/99 Black Oil Model Phase Options Figure 77: Black oil phase options • There can be one, two or three active phases: OIL, WATER and GAS. • The OIL phase can have a dissolved gas component specified by DISGAS • The GAS phase can have a vaporised oil component specified by VAPOIL • Single-phase runs cannot have components that form another phase. RUNSPECKeywords 3 Liveoil with dissolvedgas Water OIL,GAS,DISGAS,WATER 3 Water Wetgaswith vaporisedoil GAS,OIL,VAPOIL,WATER 3 Liveoil with dissolvedgas Water Wetgaswith vaporisedoil OIL,GAS,DISGAS,VAPOIL, WATER 2 Deadoil Water OIL,WATER 2 Water Drygas GAS,WATER 2 Deadoil Drygas OIL,GAS 1 Deadoil OIL 1 Water WATER 1 Drygas GAS PhaseCombination
- 231. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 231 of 499 08/04/99 Black Oil Model Phase Options Three-phase simulations In three phase simulations OIL, WATER and GAS are present and specified in the RUNSPEC section. In this case there must be either live oil or a wet gas. Either gas may come out of solution when the oil crosses the bubble point line or oil condenses from the vapour phase when the gas crosses the dew point line depending on whether the phase mixture is to the left or right of the critical point in Figure 64. • In a three-phase model at the left of the critical point the system must be saturated oil, below the critical temperature and pressure. The gas is a dry gas but the oil contains a gas component, which may come out of solution. The RUNPSEC keywords are OIL, WATER, GAS and DISGAS. There may also be some variation of gas-oil ratio with depth, which is set during initialisation using the RSVD keyword in the SOLUTION section. Alternatively, the variation of bubble point with depth can be set using PBVD in the SOLUTION section. The value of Rs may change during the run. • In a three-phase model to the right of the critical point the system must be a gas condensate. The oil is dead oil but the gas contains a volatile oil component, which may condense form the vapour phase. The RUNPSEC keywords are OIL, WATER, GAS and VAPOIL. There may also be some variation of oil-gas ration with depth, which is set during initialisation using the RVVD keyword in the SOLUTION section. Alternatively, the variation of bubble point with depth can be set using PDVD in the SOLUTION section. The value of Rv may change during the run. Two-phase simulations In two-phase simulations the phase options are OIL and WATER, WATER and GAS, GAS and OIL. • In a WATER and OIL system the gas phase is not specified so there cannot be free gas. The oil remains above bubble point. A constant Rs value can be set for the oil in each PVT region using RSCONST or RSCONSTT. RSVD may not be used. • In a GAS and WATER system the oil phase is not specified so there cannot be liquid oil. The gas does not cross the dew point line. A constant Rv value can be set for the gas in each PVT region using RVCONST or RVCONSTT. RVVD may not be used. • In an OIL and GAS system the gas may be permitted to dissolve in the oil and the oil may be permitted to evaporate into the gas. Either or both (or neither if appropriate)
- 232. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 232 of 499 08/04/99 VAPOIL and DISGAS keywords may be used. The RSVD and / or RVVD keywords may be used as appropriate. Single phase simulations Only one phase can exist in the model. This may be OIL, WATER or GAS. • In an oil simulation the gas phase is not specified so the oil remains above bubble point at all times. A constant Rs value can be set for the oil in each PVT region using RSCONST or RSCONSTT. RSVD may not be used. • In a gas simulation the oil phase is not specified so the gas does not cross the dew point line. A constant Rv value can be set for the gas in each PVT region using RVCONST or RVCONSTT. RVVD may not be used. • In a water simulation only the water phase is present.
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- 234. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 234 of 499 08/04/99 Defining Multiple PVT Types using PVT Regions Figure 78: Two oil types modelled using distinct PVT regions • The default means of modelling multiple oil types in distinct regions is to assign a complete set of PVT properties to each distinct region. • Each cell in each region is assigned a value of PVTNUM in the REGIONS section • PVTNUM is an integer which indicates which set of PVT tables should be used in a given cell • Multiple PVT tables are entered under each relevant keyword • The tables are numbered in order of entry • Identical tables may be defaulted. This may happen if, for instance, oil PVT varies but properties of other fluids do not. • Fluids flowing into a cell assume the PVT properties of that cell RUNSPEC --Specify table numbers and --dimensions in TABDIMS PROPS PVTW --2 water tables PVDO --2 dead oil tables GRAVITY --surface gravities for 1st --& second set of fluids RSCONSTT --GOR for 1st & 2nd oil REGIONS EQUALS --Array Value I1 I2 PVTNUM 2 / PVTNUM 1 1 10 / / COPY ’PVTNUM’ ’EQLNUM’ / / Oil described by the first set of PVT tables is associated with cells having PVTNUM=1 Oil described by the second set of PVT tables is associated with cells having PVTNUM=2
- 235. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 235 of 499 08/04/99 Defining Multiple PVT Types using PVT Regions If the reservoir can be subdivided into regions where the PVT properties are distinctly and significantly different, the simplest approach to modelling the variation in properties is to provide tables of PVT properties for each region. Space for the tables must also be reserved in the RUNPSEC section. How to define multiple PVT types using PVT regions As an example consider a 20*5*10 dead oil and water model which has oils of different bubble point and surface density within the boxes (1-10, 1-5, 1-10) and (11-20, 1-5, 1- 10). The relevant PVT keywords may be PVTW 4000 1.03 3.0E-6 0.40 .00 / Water PVT table 1 --Water PVT table 2 is defaulted i.e. the same as table 1 / PVDO 2500 1.260 0.5 3000 1.257 0.5 3500 1.254 0.5 4000 1.251 0.5 4500 1.248 0.5 / Dead oil PVT table 1 2550 1.191 0.5 3050 1.198 0.5 3550 1.205 0.5 4050 1.213 0.5 4550 1.220 0.5 / Dead oil PVT table 2 GRAVITY 32 1.050 0.700 / Surface gravity table 1 33.5 1.050 0.700 / Surface gravity table 2/ RSCONSTT 0.656 2500 / Bubble point GOR for oil in table 1 0.670 2550 / Bubble point GOR for oil in table 2 Any gas PVT tables would have to be treated in a similar manner. Additional RUNSPEC keywords required in this case would be TABDIMS --NTSFUN NTPVT
- 236. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 236 of 499 08/04/99 1* 2 / where NTSFUN is the number of saturation function tables entered and NTPVT is the number of PVT tables entered. Each PVT region must be defined using PVTNUM in the REGIONS section. Here the relevant keywords would be REGIONS EQUALS ’PVTNUM’ 1 / ’EQLNUM’ 1 / ’PVTNUM’ 2 11 20 / ’EQLNUM’ 2 11 20 / / EQLNUM regions corresponding to the PVTNUM regions must be defined because ECLIPSE requires that each PVT region be equilibrated separately. There is an additional requirement to define the number of equilibration regions in RUNSPEC using the EQLNUM keyword. Subdivision of the reservoir into regions and equilibration are discussed in more detail in other sections of the ECLIPSE 100 USER COURSE. Although straightforward to implement, the main disadvantages of the default treatment of multiple oil types are: • It is not realistic to expect fluid PVT properties to depend on which cell the fluid happens to be located in. • Convergence problems may arise. For instance, consider oil with a GOR of 0.5 flowing into a cell having a maximum GOR of 0.4. In order to conserve mass, gas must be liberated and free gas will form. If this has not been anticipated by supplying adequate gas PVT data in the PVDG keyword, ECLIPSE will extrapolate the gas PVT table as required. As discussed on p. 224 the extrapolation may be unreliable due to insufficient data.
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- 238. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 238 of 499 08/04/99 Defining Multiple PVT Types using API Tracking Figure 79: API tracking keywords and initial oil API • Using API tracking the initial oil API is set in the model. Water and gas PVT is unaffected • ECLIPSE tracks the density of oil in each cell • Oil surface density can be found from the PVT tables • The proportions of different density oils in a cell can be calculated from the flow • The mixture surface density is the surface density of the component oils weighted by their concentrations • The oil mixture PVT table is interpolated in each cell from the component oils in proportion to their concentrations. • Mixture density at reservoir conditions is then calculated from the PVT tables • Use the API keyword in RUNSPEC to activate this option • Define the initial oil API using OILAPI or APIVD. Do not divide the reservoir into distinct PVT and equilibration regions RUNPSEC --Activate API tracking API -- -- PROPS --As a minimum:- --A full set of fluid PVT --tables is --required for the lowest and highest --API gravities --Other PVT data as normal -- SOLUTION --Specify initial oil API using --either --OILAPI (one value per --cell) or --APIVD (as a function of --depth) --Other SOLUTION data --as normal
- 239. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 239 of 499 08/04/99 Defining Multiple PVT Types using API Tracking The API tracking option is used to calculate the PVT properties of mixtures of different oils. How to Implement API Tracking • The API keyword must be used in the RUNPSEC section. • The option does not require the reservoir to be subdivided into PVT and equilibration regions. • In the SOLUTION section the initial oil API gravity is specified either on a cell by cell basis using the OILAPI keyword or as a function of depth using APIVD. • At least two sets of PVT tables must be supplied. These must span the entire range of initial oil API gravities. • Memory must be reserved for the PVT tables using TABDIMS in the RUNPSEC section. • Since API tracking only calculates the oil PVT properties, duplicate PVT tables for gas and water may be defaulted. During the simulation: - • ECLIPSE calculates the amounts of various API oils flowing from cell to cell. • The surface density of each oil is calculated • An intermediate density is linearly interpolated based on the proportions of each oil present. • Intermediate PVT properties are calculated on the same basis. • The PVT properties are then adjusted to reservoir conditions. For instance, suppose 20° API displaces half the oil in a cell of 30° API oil. These are surface densities. ECLIPSE calculates the surface density of the oil mixture as 25° API. Effectively, this is used for the ρo (s) term in the oil EoS. A new set of PVT properties will be applied to the oil; these are halfway between the PVT tables of 20° and 30° oil. This method of modifying the PVT properties of oil mixtures has the following advantages: - • Intermediate oil mixtures can be taken into account. • Oil PVT properties do not change when flowing from one cell to another Its principal disadvantage is -
- 240. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 240 of 499 08/04/99 • ECLIPSE interpolates linearly between PVT tables in proportion to the mass of each different oil, but the variation of oil properties with API is not linear. A number of PVT tables must be supplied at intermediate oil densities to ensure that the interpolation produces valid results. The greater that number, the better the results are likely to be Example API Tracking Data As an example consider oil which varies from 40° at 10800 feet to 24° at 11920 ft. Gas and water PVT properties do not vary within the reservoir. The API gravity has been measured at eight depths. The PROPS section for fluid properties may contain the following: PVDG -- Dry gas PVT table No 1. 15 235 .008 500 6.711 .0109 1000 3.145 .0139 1500 1.987 .0168 2000 1.431 .0197 2500 1.117 .0226 3000 .923 .0256 3500 .798 .0285 4000 .716 .0314 4500 .663 .0344 5000 .630 .0373 5500 .612 .0402 5600 .609 .0408 6000 .599 .0431 6500 .596 .0460 / --Dry gas PVT table No.2 and all others default to table No.1 --because API tracking only affects only oil./ / / / / / / PVTO -- Live oil PVT table No.1
- 241. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 241 of 499 08/04/99 .200 600 1.185 .60 / .400 1400 1.285 .60 / .622 2200 1.395 .60 / .686 2420 1.430 .60 / .746 2650 1.460 .60 / .804 2830 1.485 .60 / .900 3130 1.530 .60 / 1.050 3590 1.600 .60 / 1.358 4430 1.750 .60 6500 1.738 .60 / 1.882 5600 2.020 .60 6500 2.000 .60 / 2.285 6500 2.230 .60 7000 2.218 .60 / / Live oil PVT tabvle No.2 .200 700 1.190 .60 / .400 1500 1.295 .60 / .622 2350 1.400 .60 / .686 2570 1.430 .60 / .746 2800 1.465 .60 / .804 2990 1.490 .60 / .900 3290 1.535 .60 / 1.050 3750 1.605 .60 / 1.358 4600 1.745 .60 6500 1.700 .60 / 1.882 5970 1.970 .60 / 2.285 7020 2.140 .60 7500 2.126 .60 / / Live oil PVT table No.3 .200 770 1.190 .60 / .400 1610 1.300 .60 / .622 2460 1.405 .60 / .686 2700 1.435 .60 / .746 2920 1.470 .60 / .804 3110 1.495 .60 / .900 3430 1.535 .60 / 1.050 3900 1.595 .60 6500 1.530 .60 / 1.358 4850 1.720 .60 / 1.882 6470 1.930 .60 / 2.285 7720 2.090 .60
- 242. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 242 of 499 08/04/99 8000 2.081 .60 / / Live oil PVT table No.4 .200 830 1.195 .60 / .400 1700 1.305 .60 / .622 2600 1.410 .60 / .686 2840 1.440 .60 / .746 3060 1.470 .60 / .804 3270 1.495 .60 / .900 3600 1.535 .60 6500 1.470 .60 / 1.050 4120 1.595 .60 / 1.358 5130 1.715 .60 / 1.882 6850 1.920 .60 / 2.285 8170 2.070 .60 8500 2.060 .60 / / Live oil PVT tables 5, 6, 7 & 8 default to table 4 / / / / PVTW -- Water PVT table No 1 5000 1.0000 3.0E-6 0.3 0 / --Water PVT Tables 2-8 default to table No. 1 --because API tracking affects only the oil phase/ / / / / / / ROCK -- Rock compressibility table 1 50003.5E-06 / -- Rock compressibility tables 2-8 default to table 1 / / / / /
- 243. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 243 of 499 08/04/99 / / GRAVITY -- 8 tables of surface API gravity 40.0 1.16 0.824 / 38.7 1.16 0.824 / 36.4 1.16 0.824 / 34.5 1.16 0.824 / 31.9 1.16 0.824 / 29.7 1.16 0.824 / 26.8 1.16 0.824 / 24.0 1.16 0.824 / SOLUTION APIVD --8 values of API versus depth 10800 40.0 11100 38.7 11350 36.4 11500 34.5 11670 31.9 11740 29.7 11810 26.8 11920 24.0 /
- 244. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 244 of 499 08/04/99 Rock Compressibility Figure 80: Rock compressibility • Rock compressibility must be specified since the pore volume varies under pressure • If rock compressibility is reversible and the same everywhere use the ROCK keyword. No RUNPSEC data is needed in this case. • If not, use the rock compaction option • Set the compressibility and hysteresis options using ROCKCOMP in RUNSPEC • Use ROCKTAB or ROCKTABH to define the rock compaction data, including pore volume and transmissibility multipliers versus pressure • ROCKTAB is used to define reversible compressibility • ROCKTABH is used to define irreversible compressibility i.e. compaction hysteresis. • Use ROCKNUM to assign regions of different rock type in conjunction with multiple ROCKTAB or ROCKTABH tables • The OVERBURD keyword can be used in either case to specify rock overburden tables PP V V where P V V C ilityCompressib ∂ ∂ = ∂ ∂ ∂ ∂ −= φ φ 11 1 D e p t h Pressure (psia) Fluid (hydrostatic) pressure Overburden (hydrostatic + rock) pressure 14.7 φ Overburden pressure P For reversible, non-hysteretic compressibility use ROCK --Reference Compressibility --Pressure --Use ROCKNUM array for multiple --rock compressibilities
- 245. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 245 of 499 08/04/99 Rock Compressibility The pore volume varies with pressure as ( ){ }SRSR PPCPVPV −−= exp EQ. 40 Which is represented in ECLIPSE as ( ) ( ) − +−−≅ 2 1 22 SR SRSR PPC PPCPVPV EQ. 41 where the superscripts R and S refer to reservoir and surface pressures, respectively and C is the rock compressibility. ECLIPSE uses this approximate form. The ROCK keyword is used to set a uniform compressibility within each PVT region i.e. the number of tables following ROCK must be the same as the number of PVT tables used, as set by NTPVT in RUNSPEC keyword TABDIMS. If the 43rd switch of OPTIONS is set the rock compressibility tables are associated with saturation regions (SATNUM) instead of PVT regions (PVTNUM). ROCKTAB and ROCKTABH are used to set reversible and hysteretic rock compressibility, respectively. Either keyword is followed by NTROCC tables, as set in RUNSPEC keyword ROCKCOMP. Each table consists of columns of pressure, pore volume multiplier and corresponding transmissibility multiplier.
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- 248. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 248 of 499 08/04/99 Purpose of Saturation Functions Figure 81: Required saturation function data for the PROPS section • The minimum data required is capillary pressure and relative permeability for each active phase • The data is entered in tabular form as functions of saturation • This portion of the course is restricted to saturation functions and endpoint scaling in general. • ECLIPSE has no facilities for calculating rock property data from user-defined correlations.
- 249. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 249 of 499 08/04/99 Purpose of Saturation Functions The saturation function specification has several purposes: • To specify the upper and lower limits on the saturation of each active phase. This is used at a later stage to determine the initial saturation of each phase in the gas, oil and water zones • To specify capillary pressures so that the initial transition zone saturation of each phase can be calculated • To provide the relative permeability data required to calculate fluid mobility and solve the flow equations between cells and from cell to well and vice versa. All the data must be supplied in tabular form. ECLIPSE has no facilities for calculation of rock property data based on input correlations during simulation. If correlations are to be used the data must be generated beforehand using a pre-processor such as GRID and included in the ECLIPSE data file in tabular form.
- 250. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 250 of 499 08/04/99 Saturation Functions Figure 82: Saturation function keyword families • Saturation functions are tables of relative permeability and capillary pressure • Data must be specified for any active fluid • This data is used to determine the reservoir initial oil, water, and gas saturations • The minimum data required depends on the phases present Family1 SWOF Krw, Krow, Pcowvs. Sw@connategas SGOF Krg, Kgog, Pcogvs. Sg@connatewater SLGOF Krg, Kgog, Pcogvs. Sl @connatewater Family2 SWFN Krw, PcwvsSw In3-phaseor oil-water systemsthisisat connategas SGFN Krg, Pcgvs. Sg In3-phaseor oil-gassystemsthisisat connatewater SOF3 Kro, KrgvsSo SOF2 KrovsSo SOF32D KrovsSwandSg
- 251. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 251 of 499 08/04/99 Saturation Functions A saturation function is a table of relative permeability and capillary pressure versus saturation. This must be supplied for all the phases present in the simulation for two reasons: • During initialisation ECLIPSE uses the upper and lower values of saturation from each table to determine the initial saturation distribution • Relative permeability and capillary pressure are essential to calculate interblock flow • There are two sets of keywords that may be used to input saturation function data. They are as shown in Figure 82 Saturation Function Definition The rules for table structure and design are: • Each takes the form of multiple columns of data • There must be the same number of entries in each column of any given table. • The number of rows of data in each table must be at least two and no greater than NSSFUN in the TABDIMS keyword in the RUNPSEC section. • If multiple tables are in use their number must be specified using NTSFUN in the RUNPSEC section. • Phase saturation and the relative permeability of the displacing phase should be between 0 and 1 and increase monotonically down the column, excepting the SOF2, SOF3 and SOF32D keywords. • The relative permeability of the displaced phase should be between 0 and 1 and decrease monotonically down the table column, excepting the SOF2, SOF3 and SOF32D keywords. • Capillary pressures should be positive or zero and level or decreasing down the table. • Saturation values may not be defaulted • Defaulted relative permeability values will be interpolated by ECLIPSE. • Defaulted relative permeability or capillary pressure values must be specified using 1*, 2* or 3*; they may not be left blank
- 252. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 252 of 499 08/04/99 • Each table is terminated by a forward slash (/) and each keyword may contain multiple tables. • The entire table may be defaulted using a forward slash, provided it is not the first. • So+Sw+Sg=1 always. This check is applied by ECLIPSE in a number of different forms to the endpoints of the saturation tables. Saturation Function Keyword Family 1 These are SWOF, SGOF and SLGOF.A description of each follows. SWOF This keyword may be used in runs containing both oil and water. If gas is also an active phase the oil/gas saturation functions must be input with either SGOF or SLGOF. SWOF --1 2 3 4 --Sw krw krow Pcow 0.2 0.00 0.90 4.0 0.3 0.05 0.75 2.0 0.4 1* 0.55 1.0 0.5 2* 0.5 0.6 3* 0.7 0.40 0.00 0.10 / i.e. columns of water saturation, water relative permeability, oil relative permeability when only oil and water are present and water-oil capillary pressure. The oil/water relative permeability is the two-phase relative permeability. This table should be interpreted as oil-water relative permeability at the connate gas saturation. This point is rarely significant since connate gas saturation is usually zero. If mobile gas is present the oil/water relative permeability at the maximum oil saturation must be the same as the oil-gas relative permeability at the minimum gas saturation. That is, krow at So=1- Swco equals krog at Sg=0. SGOF This keyword can be used in runs with oil and gas as active phases. If water is also active the oil/water saturation functions must be input using SWOF. SGOF --1 2 3 4 --Sg krg krog Pcog
- 253. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 253 of 499 08/04/99 i.e. columns of gas saturation, gas relative permeability and oil/gas relative permeability at the connate water saturation. This table should be interpreted as two-phase oil/gas relative permeability at the connate water saturation. If mobile water is present the oil/gas relative permeability at the connate gas saturation should equal the oil/water relative permeability at the maximum oil saturation. That is krog at Sg=0 equals krow at So=1-Swco. SLGOF This keyword may be used in runs having oil and gas as active phases. If water is also active, then the oil/water saturation functions must be input using SWOF. SLGOF --1 2 3 4 --Sl krg krog Pcog i.e. columns of liquid saturation, gas relative permeability, oil/gas relative permeability and oil/gas capillary pressure. Saturation Function Keyword Family 2 These are SWFN, SGFN, SOF3, SOF2, SOF32D. A description of each follows. SWFN This is used to specify the water saturation function. SWFN --1 2 3 --Sw krw Pcow 0.2 0.00 4.0 0.3 0.05 2.0 0.4 1* 1.0 0.5 1* 0.5 0.6 2* 0.7 0.40 0.10 / i.e. columns of water saturation, water relative permeability and oil/water capillary pressure. This table should be interpreted as the water relative permeability in the presence of a displaced phase, measured at the connate saturation of a third phase which may or may not be present. For instance, in an oil/water simulation, SWFN represents the oil/water relative permeability. In a three-phase run, SWFN represents the oil/water relative permeability at the connate gas saturation.
- 254. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 254 of 499 08/04/99 SGFN This is used to input gas saturation functions. SGFN --1 2 3 --Sg krg Pcog i.e. columns of gas saturation, gas relative permeability and oil/gas capillary pressure. This table should be interpreted as the gas relative permeability in the presence of a displaced phase, measured at the connate saturation of a third phase which may or may not be present. For instance, in an oil/gas simulation, SGFN represents the gas/oil relative permeability. In a three-phase run, SGFN represents the gas/oil relative permeability at the connate water saturation SOF3 This is used to input three-phase oil saturation function data. SOF3 --1 2 3 --So krow krog i.e. columns of oil saturation, oil/water relative permeability at the connate gas saturation and oil/gas relative permeability at the connate water saturation. SOF32D This is used to input three-phase oil saturation function data. It is an alternative to the SOF3 keyword and allows the user to input oil relative permeability in a table as a function of both water and gas saturation. A table of SOF32D data is required for each set of saturation functions specified in NTSFUN (see the TABDIMS keyword in the RUNSPEC section). For example, with NTSFUN=1 SOF32D --First table --The first line is a series of water saturation values 0.22 0.27 0.32 0.42 0.47 0.52 0.57 0.72 0.78 / --Each successive row contains gas saturation followed by kro --at the given Sg and corresponding Sw in the first row --terminated by a forward slash 0.00 1.00 0.625 0.345 0.113 0.083 0.053 0.023 0.002 0.000 / 0.05 0.555 0.337 0.210 0.078 0.047 0.021 0.004 0.000 / 0.10 0.330 0.212 0.106 0.042 0.019 0.003 0.002 0.000 / 0.15 0.215 0.103 0.069 0.017 0.003 0.002 0.001 0.000 / 0.20 0.100 0.065 0.031 0.002 0.002 0.001 0.000 / 0.25 0.060 0.025 0.014 0.001 0.001 0.000 /
- 255. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 255 of 499 08/04/99 0.30 0.020 0.012 0.001 0.001 0.000 / 0.35 0.010 0.001 0.001 0.000 / 0.40 0.000 0.000 0.000 / / end of table 1 SOF2 This is used to input two-phase oil relative permeability data. SOF2 --1 2 --So kro 0.2 0.90 0.3 0.75 0.4 0.55 0.5 1* 0.6 1* 0.7 0.00 / i.e. oil saturation versus oil relative permeability. This should be interpreted as the oil relative permeability in the presence of one other phase.
- 256. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 256 of 499 08/04/99 Three-Phase Relative Permeability Figure 83: Default three-phase oil relative permeability calculation • The default ECLIPSE method is a linear sum of the two-phase relative permeabilities weighted by the fraction of the cell occupied by each. • The default ECLIPSE method assumes full segregation within the cell. • The modified STONE1 and STONE2 methods are also available wrowgrogro HkHkk += wcowg wcow w SSS SS H −+ − = wcowg g g SSS S H −+ = STONE1 and STONE2 are also available. Use keywords STONE1 and STONE2 respectively. WATER OIL GAS Swco 1-So -Swco So 1-So In the Eclipse default model, fractions of mobile gas and water are: For the three-phase oil rel. perm. use a simple mixing rule:
- 257. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 257 of 499 08/04/99 Three-Phase Relative Permeability Eclipse Default The ECLIPSE default three-phase relative permeability calculation is a weighted sum of the two-phase relative permeabilities. It assumes full segregation of fluids within the cell. Although this is rare, the model is robust and has been used extensively and found adequate. Modified STONE1 An alternative three-phase relative permeability model available in ECLIPSE is a modification of the first model suggested by Stone in 1970 [4]. The STONE keyword activates this calculation. A more comprehensive explanation can be found in the ECLIPSE 100 TECHNICAL APPENDICES. Modified STONE2 The third three phase relative permeability calculation option available in ECLIPSE is a modification of Stone’s second model proposed in [5]. The STONE2 keyword activates this calculation. The STONE2 method may produce negative values of oil relative permeability. In this event, ECLIPSE resets the calculated value to zero. A more comprehensive explanation can be found in the ECLIPSE 100 TECHNICAL APPENDICES.
- 258. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 258 of 499 08/04/99 Saturation Function Scaling Figure 84: Significant saturation endpoints • The aim is to supply relatively few generic saturation functions • The saturation functions are transformed and applied to the existing rock types • There are three main types of scaling: • Scaling of the saturation axis for relative permeability and capillary pressure modification (“endpoint scaling”) • Scaling of relative permeability values (“vertical scaling”) • Capillary pressure scaling • All saturation functions are a type of pseudofunction because they are all scale- dependent • Saturation function scaling is the simplest means of pseudofunction generation. SWL SWCR SWU krwkrow Pcow SOWCR SGL SGCR krg krog Pcog SOGCR SGU
- 259. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 259 of 499 08/04/99 Saturation Function Scaling The purpose of saturation function scaling is to supply a small number of saturation functions with a generic form that applies to a number of rock types. The endpoints, or maximum and minimum values, of the generic curves do not of course apply to every rock type. Saturation function scaling then transforms the generic curves so that they may be applied to the existing rock types. The transformation is in general linear. The implementation of each type of scaling is slightly different
- 260. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 260 of 499 08/04/99 Endpoint Scaling Figure 85: Effect of saturation scaling • Saturation scaling is a linear transformation of the saturation axis • This is usually known as endpoint scaling • Saturation table endpoint s are supplied on a cell-by-cell basis or as a function of depth
- 261. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 261 of 499 08/04/99 Endpoint Scaling Saturation scaling is a linear transformation of the saturation axis as follows t l t u t u s l s u ss u SS SS SS SS − − = − − EQ. 42 Where the superscripts s and t denote scaled and tabular values, respectively and subscripts u and l denote upper and lower saturation endpoints, respectively. Scaled upper and lower saturation values are endpoints supplied by the user whereas the tabular values are read by ECLIPSE from the generic saturation functions. Rearranging EQ. 42 gives BASS S += EQ. 43 for a nominated phase. ECLIPSE calculates and stores the coefficients A and B. During saturation function lookup ECLIPSE uses the transformed value Ss instead of S. How to Implement Endpoint Scaling In a three-phase model there are a number of significant saturation endpoints which may be endpoint scaled. These endpoints may be set on a cell-by-cell basis or within boxes: • SWL is the connate water saturation, often denoted as Swco. This is the lowest water saturation value in any given water saturation function and is often termed the irreducible water saturation. • SWCR is the critical water saturation, often denoted Swcr. This is the highest water saturation in any given table for which water is immobile (krw =0). • SWU is the maximum water saturation, often denoted Swu. This is the highest water saturation value in any given water saturation function. • SGL is the connate gas saturation, often denoted as Sgco. This is the lowest gas saturation value in any given gas saturation function • SGCR is the critical gas saturation, often denoted Sgcr. This is the highest gas saturation in any given table for which gas is immobile (krg =0).
- 262. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 262 of 499 08/04/99 • SGU is the maximum gas saturation, often denoted Sgu. This is the highest gas saturation value in any given gas saturation function. • SOWCR is the critical oil-water saturation, often denoted Sowcr. This is the largest oil saturation at which oil is immobile in water. • SOGCR is the critical oil-gas saturation, often denoted Sogcr. This is the largest oil saturation at which oil is immobile in gas. NOTE that in EQ. 42 only two endpoints are used by default for each phase. These are the critical and maximum saturations and the critical oil/water and oil/gas saturations. The SCALECRS keyword can and should be used during endpoint scaling to preserve the relative permeability at the critical saturations of oil and gas. See 2-Point and 3-Point Endpoint Scaling, p.263. As an alternative the endpoints may vary as a function of depth using the ENPTVD keyword. Its syntax is ENPTVD --1 2 3 4 5 6 7 8 9 --Depth SWL SWCR SWU SGL SGCR SGU SOWCR SOGCR and it must contain at least two rows of data. There may be a number of ENPTVD tables, each separated by a forward slash. Each ENPTVD table is assigned to a set of generic saturation functions using the ENDNUM keyword in the REGIONS section. Endpoint scaling (EPS) is activated using the ENDSCALE keyword in the RUNPSEC section. The default EPS options within ENDSCALE are: • ‘NODIR’ that is the EPS is not directional by default. The same saturation table is used for flow in the X (or I), Y (or J) and Z (or K) directions. If directional EPS is active (‘DIRECT’ option within SATOPTS) then endpoints must be assigned to each cell face. The keywords used for this are the same as the endpoint keywords below but with a suffix X, X-, Y, Y- Z or Z-. • ‘REVERS’ that is endpoint scaling is reversible by default. The same table is used whether flow is from I to I+1 or from I to I-1. If EPS is irreversible the endpoints are entered under the appropriate directional endpoint keywords as above. Alternatively, they may be entered as functions of depth using the directional versions of ENPTVD, which are ENPTVDX, ENPTVDX-, ENPTVDY, ENPTVDY-, ENPTVDZ and ENPTVDZ-.
- 263. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 263 of 499 08/04/99 2-Point and 3-Point Endpoint Scaling By default ECLIPSE preserves the relative permeability at two points. For each phase these are: krw SWCR & SWU krg SGCR & SGU krow SOWCR & (1-SWL-SGL) krog SOGCR & (1-SWL-SGL) When for example the oil/water saturation functions are scaled, this usually leads to: altered water relative permeability at the minimum mobile oil saturation and altered oil/water relative permeability at the minimum mobile water saturation. This directly influences water cut. Similar comments apply to gas-oil ratios. To prevent this, the three-point scaling option can be enabled with the SCALECRS keyword. A graphical example of the difference between two- and three-point EPS is shown in Figure 86. Figure 86: Two-Point and Three-Point Endpoint Scaling Three-point EPS preserves the relative permeability at the following saturations: krw SWCR, (1-SOWCR-SGL) & SWU krg SGCR, (1-SOGCR-SWL) & SGU krow SOWCR, (1-SWCR-SGL) & (1-SWL-SGL) 2 pt 3 pt Unscaled Scaled Krw at (1-SOWCR-SGL) changes Krw at (1-SOWCR-SGL) fixed Krow at (1-SWCR-SGL) changes Krow at (1-SWCR-SGL) fixed
- 264. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 264 of 499 08/04/99 krog SOGCR, 1-SGCR-SWL) & (1-SWL-SGL) In gas-water runs the following endpoints are used in three-point EPS: krw SWCR, (1-SGCR) krg SGCR, (1-SWCR) & SGU Limiting three-Point Endpoint Scaling In some cases where three-point EPS is used the water relative permeability curve can become almost vertical, as in the figure below. Figure 87: SCALELIM keyword effect SCALELIM allows the user to specify a minimum value for SWU-(1-SOWCR). This is in the interest of preventing convergence problems that may be caused by vertical or near- vertical relative permeability curves. SCALELIM applies only to the water relative permeability. SCALELIM = SWU-(1-SOWCR) krw Sw
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- 266. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 266 of 499 08/04/99 Vertical scaling Figure 88: Vertical saturation function scaling • Vertical scaling is a multiplier applied to grid cell relative permeability • It is applied at the maximum and the critical or irreducible saturation phase saturation • It may honour the relative permeability at the critical saturation of the displacing phase • The scaling can be applied on a cell-by-cell basis or as a function of depth RUNSPEC ENDSCALE ’NODIR’ ’REVERS’ / PROPS EQUALS --Array Value KRW 0.95 / KRWR 0.95 / KRG 0.95 / KRGR 0.95 / KRORW 0.95 / KRORG 0.95 / /
- 267. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 267 of 499 08/04/99 Vertical scaling Vertical scaling of relative permeability is a scale factor applied to the grid cell relative permeability. The available options are • Scaling the relative permeability at the maximum phase saturation. For oil and gas this is usually at the connate water saturation. For water this is at the maximum water saturation. The keywords used to do this are KRW, KRG and KRO • Additionally the relative permeability at the critical saturation of the displacing phase may be honoured. The keywords used to do this are KRWR, KRGR, KRORW and KRORG. As an alternative, depth variation may be specified using the ENKRVD keyword, which takes the form ENKRVD --1 2 3 4 5 6 7 8 --Depth krw krg kro krw at krg at kro at kro at -- Socr or Sgcr Socr or Swcr Sgcr Swcr Endpoint scaling must be enabled in the RUNPSEC section using the ENDSCALE keyword. Consider the effect upon oil. If the KRO keyword is used the relative permeability is multiplied as follows after any scaling of saturation endpoints KRO k k k t ro t ro ro max = EQ. 44 Where kro t is oil relative permeability read from the supplied saturation table kro t max is the highest oil relative permeability in the supplied saturation table KRO is the oil relative permeability supplied by the user in the KRO keyword. The relative permeability is taken at either the maximum saturation in the table or at SWL, if specified. If the KRORW or KRORG keywords are specified then the scaling honours the relative permeability at the critical saturation of the displacing phase. The critical saturation is • 1-SWCR for KRORW • 1-SGCR for KRORG
- 268. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 268 of 499 08/04/99 A more comprehensive description may be found in the ECLIPSE 100 TECHNICAL APPENDICES in the chapter titled “Saturation Table Scaling” as well as in the ECLIPSE 100 REFERENCE MANUAL under the appropriate keyword. NOTE that if directional and/or reversible EPS is enabled, then cell face relative permeabilities are set by one of two ways: firstly on a cell-by-cell basis using directional relative permeability keywords KRWX/X-/Y/Y-/Z/Z-, KROX/X-/Y/Y-/Z/Z- , KRGX/X-/Y/Y-/Z/Z-, KRORWX/X-/Y/Y-/Z/Z- and KROGX/X-/Y/Y-/Z/Z-. Secondly, as a function of depth using the ENKRVDX/X-/Y/Y-/Z/Z- keywords.
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- 270. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 270 of 499 08/04/99 Capillary Pressure Scaling Figure 89: Capillary pressure scaling • There are several ways to scale capillary pressure • Capillary pressure scaling is a multiplier applied to the capillary pressure • The Leverett J Function correlates capillary pressure to permeability and porosity • Capillary pressure may be a function of pressure via the interfacial tension • Capillary pressure scaling is also a part of saturation endpoint scaling. Refer to the section named Endpoint Scaling on p.260. éVertical Pc scaling by a designated factor Use the PCW, PCG keywords éHorizontal Pc scaling Use SWLPC, SGLPC éThe Leverett J Function Pc=UPc t σ(φ/Κ)0.5 Use the JFUNC keyword in the GRID section to activate oil / water / gas J function scaling éPressure dependence Pc α σ and σ=σ(P) Use STOW, STOG for IFT vs. pressure
- 271. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 271 of 499 08/04/99 Capillary Pressure Scaling Vertical Capillary Pressure Scaling The maximum capillary pressure value within a given grid cell can be scaled on a cell by cell basis. The maximum values are specified with the PCW and PCG keywords for the oil/water and oil/gas capillary pressures, respectively. Using the water/oil case as an example, the capillary pressure is modified to maxt cow t cowcow P PCW PP = EQ. 45 Where Pcow is the modified capillary pressure Pcow t is the capillary pressure from the saturation function Pcow tmax is the maximum capillary pressure supplied in the saturation function PCW is the maximum capillary pressure permitted, as set in the PCW keyword. Horizontal Capillary Pressure Scaling The capillary pressure can be scaled horizontally, independently of the relative permeability. The method of scaling is the same as two-point saturation function scaling (see the notes on page 263). Capillary pressure endpoints are specified using SWLPC and SGLPC for water and gas, respectively. The option is enabled by the ENDSCALE keyword in the RUNSPEC section. The Leverett J Function The J function is a capillary pressure correlation to porosity and permeability. The dimensionless J function takes the place of the capillary pressure curves entered using the SGFN, SWFN, SWOF, SGOF or SLGOF keywords. The capillary pressure is calculated from K UPP t cc φ σ= EQ. 46 Where Pc is the capillary pressure U is a constant which value is set depending on the choice of FIELD, METRIC or LAB units
- 272. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 272 of 499 08/04/99 Pc t is capillary pressure from the input saturation function σ is the interfacial tension (IFT) K is the cell permeability, taken as ( )yx KKK += 5.0 φ is the cell porosity The capillary pressures are multiplied by a factor of K U φ σ=multiplier EQ. 47 The J function options is activated with the JFUNC keyword, which has the syntax JFUNC --1 2 3 --Flag σow σog NOTE that the JFUNC keyword is placed in the GRID section, not the PROPS section. The first item may be ‘WATER’, ‘GAS’ or ‘BOTH’ which activates the J function option for either or both oil and gas. σow is the oil/water IFT and σog is the oil/gas IFT. The resulting capillary pressures can be reported using the ENDPT mnemonic in the RPTPROPS keyword. Pressure Dependent Interfacial Tension If the IFT depends on pressure, the STOW and STOG keywords provide a means of entering the dependence. ECLIPSE then applies a scale factor to the capillary pressure as follows ( ) )(P )( r ef ot coc P PPP σ σ = where Pc(Po) is the modified capillary pressure Pc t is the capillary pressure provided in the input saturation functions σ(Po) is the IFT at the oil pressure σ(Pref) is the IFT at the reference pressure The modified capillary pressure Pc(Po) may then be further scaled by the Leverett J function. The STOW and/or STOG keywords may only be used if the ‘SURFTENS’ option in SATOPTS is active in the RUNPSEC section. The format of each keyword is STOG
- 273. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 273 of 499 08/04/99 --1 2 --Oil phase oil/gas --pressure IFT and STOW --1 2 --Oil phase oil/water --pressure IFT The number of rows in either table should not exceed NPPVT specified in the RUNSPEC keyword TABDIMS.
- 274. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 274 of 499 08/04/99 Output Control Figure 90: PROPS section output control • RPTPROPS is the only PROPS section output control keyword • A full listing of available PROPS section keywords can be found in the ECLIPSE 100 REFERENCE MANUAL • The INIT keyword in the GRID section requests an initial file which contains PVT and saturation function data. RPTPROPS --Controls output from the PROPS section --Output is directed only to the PRT file --Available mnemonics are listed in the --Eclipse 100 Reference Manual --Pre-96a format with integer controls is still usable INIT --Saturation functions and PVT data is contained --in the INIT file and can be loaded and displayed --in Graf
- 275. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 275 of 499 08/04/99 Output Control PROPS Section Output Using RPTPROPS The sole output control keyword used specifically in the PROPS section is RPTPROPS. Output is to the PRT file (or LOG file) only. It takes two types of argument The pre-96a format uses a series of integers and multiple default values. From ECLIPSE version 96a the arguments may take the form of mnemonics enclosed in quotes. For instance RPTPROPS ‘SWFN’ ‘ENDPT’ ‘STOG’ ‘STOW’ / is equivalent to RPTPROPS 1* 1 6* 1 4* 1 / The pre-96a format is compatible with subsequent releases of ECLIPSE. PROPS Section Output Using INIT The .INIT or initial file also contains the PVT and saturation functions. The saturation function data consists of unscaled tables (i.e. as input by the user) as well as endpoint scaling information. If scaled saturation functions are viewed within GRAF, the endpoint scaling is applied within GRAF to reproduce the curves used by Eclipse during the simulation. The PVT data consists of the tables input by the user plus a certain amount of extrapolated data. For live oil and wet gas data, ECLIPSE extrapolates an extra ten data points on each undersaturated curve. This is output to the initial file. The initial file is not created by default and is requested by inserting the INIT keyword anywhere in the GRID section.
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- 278. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 278 of 499 08/04/99 Purpose of the REGIONS Section Figure 91: Example REGIONS section data • The REGIONS section is optional • The REGIONS section divides the reservoir according to variations in reservoir characteristics or for reporting purposes • Most REGIONS section keywords take the form XXXNUM • For each type of region a cell is assigned a region number between 1 and the maximum allowed number of regions. • A few XXXNUM keywords do not belong in the REGIONS section • The REGDIMS keyword in RUNSPEC is used to set the upper limits on the numbers of regions.
- 279. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 279 of 499 08/04/99 Purpose of the REGIONS Section The optional REGIONS section is used for two purposes: • To assign specific properties or characteristics to cells or groups of cells. The properties are defined by tables elsewhere in the ECLIPSE data file. • To report on the fluids in place in specific parts of the reservoir For example, if the reservoir contains three different oils three sets of PVT tables would be supplied, one per region. These tables are understood to be numbered in the order of entry in the data file. Each grid cell is assigned a number between 1 to 3, depending upon the table we want the cell to use. By default every region number for each cell is 1. This number is referred to as the region number or PVT number (or PVTNUM which is the keyword used to assign these values to each cell). Cells assigned the value of 1 will use the first PVT table. Those assigned the number 2 will use the second table and those assigned the number 3 will use the third table. If there is only one PVT table, PVT regions do not need to be assigned since 1 is the default for each cell. In this case, the REGIONS section isn’t needed and can be optionally left out. Different types of regions are assigned to each grid cell to assign each cell to different types of tables.
- 280. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 280 of 499 08/04/99 Regions Keyword Types Figure 92: REGIONS Section Keywords • Region definition keywords are used to assign region numbers to each cell. This is usually to associate a table of properties with a cell or group of cells • The numbers of these types of regions is set in the RUNSPEC section • Reporting regions are parts of the reservoir for which fluid-in-place reports are produced • Additional fluid-in-place regions additional to the FIPNUM regions may be defined. The total number of fluid-in-place regions is set using REGDIMS in RUNSPEC. • Directional keywords are used for anisotropic cell properties such as directional relative permeability • All the above may be applied using the operator keywords • The output controls regulate reports in the PRT and INIT files • FLUXNUM and RESVNUM are used in the GRID section. Region definition keywords: XXXNUM e.g. PVTNUM Reporting regions FIPNUM Additional reporting regions FIPXXXXX Directional keywords: XXXNUMX/X-/Y/Y-Z/Z- Operators EQUALS, ADD, COPY, BOX ENDBOX Output Control RPTREGS, BOUNDARY INIT, RPTSCHED Exceptions FLUXNUM, RESVNUM
- 281. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 281 of 499 08/04/99 Regions Keyword Types Region definition keywords The most commonly used of these are EQLNUM, PVTNUM and SATNUM. EQLNUM associates equilibration regions with cells or groups of cells. PVTNUM, which is used to associate sets of PVT tables with specific cells. Since each PVT region contains fluids of different density, it follows that they must be equilibrated separately. So, each PVT region must correspond to an equilibration region, even if all the PVT regions have the same set of fluid contacts. The converse does not apply, however: a single set of fluids may have several different contacts. The multiple fluid contacts are each specified with a separate record in the EQUIL keyword, each separated by a forward slash (/). Duplicate records of fluid contact data after the first record can be defaulted in EQUIL. For example, a dead oil-water model with two oil types may use PROPS section keywords PVDO <table 1> / / <table 2> / / PVTW <table 1> / / / table 2 defaults to table 1 RSCONSTT <table 1> / / table 2 defaults to table 1 / and in the REGIONS section PVTNUM <PVTNUM definition>/ / COPY ‘PVTNUM’ ‘EQLNUM’ / / and in the SOLUTION section EQUIL <table 1> / / table 2 defaults to table 1
- 282. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 282 of 499 08/04/99 / The numbers of PVTNUM and EQLNUM regions, two of each in this case, is set using NTPVT in TABDIMS and NTEQUL in EQLDIMS, respectively. SATNUM is used to associate saturation functions with cells or groups of cells. The number of SATNUM regions is set using NTSFUN in TABDIMS. Fluid in Place Regions Fluid in place regions may be defined using FIPNUM, which takes an integer value for every cell in the current box. Additional fluid-in-place regions may be defined using FIPXXXXX where XXXXX is a user-defined mnemonic. The FIPNUM and FIPXXXXX regions may overlap. The total number of these regions must be set in NTFIP in REGDIMS in the RUNPSEC section. As an example, consider a 20*5*10 model. The boxes I=1 to 10 and I=11 to 20 are separate fault blocks whose fluids in place need to be reported separately and a report of fluids in place for each layer is also needed. These regions would be defined as follows: In the RUNPSEC section REGDIMS --NTFIP NMFIPR 10 10 / and in the REGIONS section REGIONS EQUALS --Array Value I1 I2 ’FIPNUM’ 1 / ’FIPNUM’ 2 11 20 / / FIPLAYER --Fiplayer is an extra fluid in place region which --takes the value 1 to 10 --FIPLAYER=1 for layer 1 100*1 --FIPLAYER=2 for layer 2 100*2 --FIPLAYER=3 for layer 3 100*3 --FIPLAYER=4 for layer 4 100*4 --FIPLAYER=5 for layer 5
- 283. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 283 of 499 08/04/99 100*5 --FIPLAYER=6 for layer 6 100*6 --FIPLAYER=7 for layer 7 100*7 --FIPLAYER=8 for layer 8 100*8 --FIPLAYER=9 for layer 9 100*9 --FIPLAYER=10 for layer 10 100*10 / Reports on both FIPNUM and FIPLAYER are written as tables in the PRT file if the ‘FIP=3’ mnemonic is used in RPTSCHED. Directional Keywords The directional keywords of the form XXXNUMX, XXXNUMX-, XXXNUMY, XXXNUMY-, XXXNUMZ, XXXNUMZ- are active if anistropic properties are in use, such as directional relative permeability. Their usage and syntax is the same as for the XXXNUM keywords mentioned above. Operators The REGIONS sections keywords are often of the form KEYWORD <1 value per cell> / but repeat values can be assigned using the operators EQUALS, ADD, COPY, BOX, ENDBOX to reduce the amount of shorthand. Also, the GRID pre-processor can generate any keyword which takes a single value per cell, including REGIONS keywords. These can be incorporated in the REGIONS section using the INCLUDE keyword. Output Controls • The mnemonics available as part of the RPTREGS keyword are used to request tabular output of REGIONS numbers to the PRT file. Pre-96a formats of RPTREGS which use a series of integers and explicit default values are compatible with later releases of ECLIPSE which utilise mnemonics in quotes to request output. • BOUNDARY is used to restrict output to the PRT file to a single defined box of cells. • The INIT keyword requests an INIT file, which contains all of the region definitions except for the additional FIPXXXXX fluid-in-place regions.
- 284. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 284 of 499 08/04/99 • The RPTSCHED keyword must be placed in the SCHEDULE section, not the REGIONS section. The mnemonic ‘FIP=3’ requests output of tabular reports on all of the fluid-in-place regions. • The keywords FLUXNUM and RESVNUM belong in the GRID section. FLUXNUM is used to define flux regions in the ECLIPSE 200 FLUX BOUNDARY OPTION and RESVNUM is used to define independent reservoir regions in ECLIPSE 100.
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- 286. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 286 of 499 08/04/99 Purpose of the SOLUTION Section Figure 93: Function of the SOLUTION section • The SOLUTION section defines the conditions at the beginning of the simulation • This is not necessarily the same as the conditions at the end of geological time, or before production • Initial conditions can be defined by equilibration, enumeration or restart • Analytical aquifers are defined in the SOLUTION section but discussed in a separate section of the ECLIPSE 100 USER COURSE • SOLUTION section data can be written to the PRT and restart files. Water
- 287. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 287 of 499 08/04/99 Purpose of the SOLUTION Section The SOLUTION section is used to define the initial conditions of the simulation. These are: • initial pressure and phase saturation for each grid cell • initial solution ratios, that is gas-oil and/or oil-gas ratio for each cell • depth dependence of reservoir fluid properties, which are API, saturated GOR, bubble point, saturated OGR and dew point versus depth. • oil and gas re-solution rates • initial analytical aquifer conditions. This is discussed in more detail in another section of the ECLIPSE 100 USER COURSE The manner these are specified depends on the choice of equilibration, enumeration or restart. Each will be discussed in turn.
- 288. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 288 of 499 08/04/99 Equilibration Figure 94: Block centre equilibration • In equilibration the contacts and a datum depth and pressure are specified • Hydrostatic equilibrium is assumed • Equilibration is appropriate for initially undrilled reservoirs with flat contacts. • There may be an entry level capillary pressure • The black oil EOS is used to calculate the hydrostatic pressure of each phase everywhere • Phase saturation in each zone is taken from the saturation functions in the PROPS section • In the transition zones Sw and Sg are set by reverse lookup of the capillary pressure curves supplied as part of the saturation functions. Pressure Depth GOC OWC FWL (Pcow=0) TZ TZ Datum GAS ZONE: Sg=SGMAX, i.e max. gas from saturation functions Sw =SWMIN, i.e. connate water, Swco from saturation functions So=1-SWMIN-SGMAX OIL ZONE: Sg=SGMIN, usually zero, from saturation functions Sw=SWMIN, i.e. connate water, Swco, from saturation functions So =1-SWMIN-SGMIN, usually So =1-Swco WATER ZONE: Sg=SGMIN, usually zero, from saturation functions Sw=SWMAX, i.e. max water, from saturation functions So=1-SWMAX-SGMIN, usually So=1-Swmax. Reverse lookup of Pcow curves to find Sw in TZ Pcow=Po-Pw Pcog=Pg-Po Pcow Sw Swi Swi applied to cell centre
- 289. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 289 of 499 08/04/99 Equilibration The equilibration option for setting initial pressures and saturations is based upon the saturation functions, fluid contacts and datum depth and pressure. If the pressure is known at a datum depth in the oil zone, then the black oil EOS for oil o s gs s or o B R )()( )( ρρ ρ + = EQ. 48 and the hydrostatic pressure of the oil phase ∫+= 2 1 12 )()( h h gdhhPhP ooo ρ EQ. 49 may be iteratively solved for oil phase pressure everywhere. Here (r) and (s) denote reservoir and surface conditions, respectively and ρo is oil density, h represents depth. Given the fluid contacts, the gas and water EOS may be solved in a similar manner to eventually yield the initial hydrostatic pressure of each phase everywhere in the reservoir. In practice, ECLIPSE calculates the phase pressures at 100 depth points evenly distributed throughout the reservoir. This may be altered by changing the NDPRVD setting in the EQLDIMS keyword in the RUNPSEC section. Since the calculation is iterative and relies on correctly locating the 100 depth points at which the pressure is calculated, it may in some cases be necessary to adjust NDPRVD to correct convergence problems in the equilibration calculation. Initial Phase Saturation Once the initial pressure has been calculated ECLIPSE assigns phase saturations in each zone. This does not include the transition zones, which are discussed below. The phase saturations are taken from the saturation endpoints defined within the saturation functions in the PROPS section, and oil saturation is always calculated from water and gas saturation. So: • In the gas zone Sg is at a maximum. This is SGU, the highest gas saturation in the input gas saturation function. Sw is at a minimum, SWL, the lowest water saturation in the input water saturation function table, i.e. connate or irreducible water saturation Swco. The oil saturation is then So=1-SGU-SWL.
- 290. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 290 of 499 08/04/99 • In the water zone Sw is at a maximum. This is SWU, the highest water saturation in the input water saturation function. This value is often 1. Sg is at a minimum, SGL, the lowest gas saturation in the input gas saturation function table, i.e. connate gas saturation Sgco. This is usually zero. The oil saturation is then So=1-SWU-SGL. Usually So=1-Swco. • In the oil zone both water and gas are at minimum values. Sg=SGL=Sgco and Sw=SWL=Swco. The oil saturation is then So=1-SWL-SGL. Usually, So=1-Swco. Initial Phase Saturation in the Transition Zone In the transition zone the phase saturation is governed by capillary pressure. The definitions of capillary pressure are wocow PPP −= EQ. 50 And ogcog PPP −= EQ. 51 which can be readily calculated at any depth as the difference between the hydrostatic pressures of the phases. ECLIPSE then uses reverse lookup of the capillary pressure curves in the input saturation functions to determine the transition zone water and gas saturations. In theory the capillary pressure curve for water extends to Pcow→∞ at Sw=0. In practice the capillary pressure curve should terminate at Swco to ensure that there is no discontinuity in Sw at the lowest water saturation in the saturation function. Consider a tilted cell intersecting the OWC as in Figure 94. The cell saturation is assigned by calculating the cell centre depth and assigning initial Soi, Swi and Sgi to the cell centre as calculated above and shown in Figure 94. This method provides a completely stable initial solution in which the phase saturation is consistent with the hydrostatic pressure. This is known as centre-block equilibration.
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- 292. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 292 of 499 08/04/99 EQUIL Keyword Usage Figure 95: EQUIL keyword parameters • In single-phase, oil-water and gas-water models the GOC is ignored • In single-phase and oil-gas models the OWC is ignored • In condensate runs initially above the dew point the OWC should be set to the same depth as the GOC • If there is only free gas with vaporised oil the GOC can lie below the formation bottom • If there is no mobile water initially the OWC can lie below the formation bottom. • The accuracy option in item 9 defaults to -5, giving level block equilibration as discussed. If N<0 or N>0 then equilibration is termed level block and tilted block equilibration, respectively. é In 3-phase and oil/water runs, EQUIL parameters are: EQUIL --1 2 3 4 5 6 --Datum Pressure OWC Pcow GOC Pcog --Depth @ Datum depth @ OWC Depth @ GOC --7 8 9 --Rs vs Depth Rv vs depth Accuracy --or Pb vs depth or Pd vs depth option --table index table index -10<=N<=10 é In gas-water runs, EQUIL parameters are: EQUIL --1 2 3 4 5 6 --Datum Pressure GOC Pcog Not Not --Depth @ Datum depth @ GOC Used Used --7 8 9 --Rs vs Depth Rv vs depth Accuracy --or Pb vs depth or Pd vs depth option --table index table index -10<=N<=10 --doesn’t apply
- 293. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 293 of 499 08/04/99 EQUIL Keyword Usage The EQUIL keyword is used to implement this type of equilibration. It is unusual because the items following EQUIL are interpreted differently depending on the phases present. In three-phase and oil/water models the parameters are as shown in Figure 95.
- 294. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 294 of 499 08/04/99 Block Centre Equilibration Figure 96: Block Centre Equilibration • Saturations are assigned at cell centres • Cells intersecting the OWC contain too much water or too much oil • The OWC is effectively jagged • The initial oil in place estimates could be estimated more accurately • Block centre equilibration is not the default method OIL ZONE: Sg=SGMIN, usually zero, from saturation functions Sw=SWMIN, i.e. connate water, Swco, from saturation functions So=1-SWMIN-SGMIN, usually So=1-Swco WATER ZONE: Sg=SGMIN, usually zero, from saturation functions Sw=SWMAX, i.e. max water, from saturation functions So=1-SWMAX-SGMIN, usually So=1-Swmax. OWC from block centre equilibration. Saturations for entire cells are assigned to cell centres. OWC TZ Cell centre In centre block equilibration the 9th Item of EQUIL = 0 The default value is -5.
- 295. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 295 of 499 08/04/99 Block Centre Equilibration Consider a cell intersecting the OWC during block centre equilibration, as in Figure 94. Since ECLIPSE assigns saturation for the entire cell based on the depth of the cell centre, a number of cells with centres above the OWC will in part lie in the water zone. Likewise, a number of cells having centres below the OWC will in part lie in the oil zone. The estimate of initial oil in place (OIP) will be inaccurate due to this, which is ultimately caused by representing the reservoir as discrete cells in the region of the OWC. NOTE that although block centre equilibration may provide an inaccurate estimate of oil in place, the initial state of the reservoir model will be stable (excluding other effects) because the pressures, saturations and capillary pressures are all consistent.
- 296. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 296 of 499 08/04/99 Level and Tilted Block Fine Grid Equilibration Figure 97: Level and Tilted Block Equilibration • Level and tilted block equilibration subdivide cells at the OWC during initialisation • Saturations are calculated for subdivisions of each cell • Saturations of subdivisions are combined to give an overall cell saturation • Level block equilibration uses average saturation • Tilted block equilibration uses pore volume weighted average saturation • Options are determined by the ninth item of the EQUIL keyword i=1 i=2 i=3 i=2N-1 i=2N OWC TZ NEQUIL N PV SPV N Sw Tilted N S N S Level N i i N i wi N i ww i i = > = < = ∑ ∑ ∑ = = = )9( 0 2 1 : 0 2 1 : 2 1 2 1 2 1 Block centre equilibration OWC Water saturation is calculated in 2N sub-cells during equilibration. In level block integration the average is used In tilted block integration sub-cell saturations are pore volume weighted. Tilted or level block integration OWC Level or tilted block equilibration require quiescence RUNSPEC EQLOPTS ’QUIESC’ /
- 297. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 297 of 499 08/04/99 Level and Tilted Block Fine Grid Equilibration Fine grid equilibration is a refinement of block centre equilibration designed to improve estimates of initial oil in place. Setting the ninth item of the EQUIL keyword to a nonzero value will invoke either level or tilted block integration: • Setting the ninth item of EQUIL positive gives tilted block integration • Setting the ninth item of EQUIL negative gives level block integration The limits upon N are-10<N<10. Each cell intersecting the OWC is subdivided during equilibration into 2N sub-cells. The phase saturation in each of these sub-cells is then calculated exactly as described above for block centre equilibration. In level block integration the sub-cell saturations are averaged. In tilted block integration the sub-cell saturations are pore volume weighted before averaging. Figure 97 illustrates the procedure. Level and titled block integration can significantly improve the OIP estimate, particularly if the cells intersecting the OWC are large and highly inclined. The cell saturations, however, are not the same as for block centre equilibration. The cell saturation is therefore inconsistent with the prevailing capillary pressure and the result is an unstable initial state. If a model using fine grid equilibration is run with no injection or production, the reservoir fluids will flow and eventually stabilise in hydrostatic equilibrium. The result will be the same as for block-centre equilibration. Two corrections must be made to guarantee stability and accurate OIP estimation. They are Quiescence and the Mobile Fluid Correction. Quiescence The object of quiescence is to stabilise the reservoir fluids in models using fine grid options (level or titled block integration). Quiescence can be described in a number of ways: • Application of endpoint scaling to the capillary pressure curves of only those cells intersecting the OWC and GOC as required to prevent flow from cell to cell in the absence of production and injection. • Modification of the water and gas hydrostatic pressure gradients to force the capillary pressure into consistency with the prevailing saturation. The former is the way quiescence is implemented in ECLIPSE.
- 298. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 298 of 499 08/04/99 Keyword Usage To activate quiescence use the ‘QUIESC’ switch in the EQLOPTS keyword in the RUNPSEC section. Note that quiescence has no effect in cases where block centre equilibration is used (i.e. when the 9th item of EQUIL is zero).
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- 300. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 300 of 499 08/04/99 Mobile Fluid Correction Figure 98: Mobile Fluid Correction • Saturations are assigned at cell centres • ECLIPSE calculates immobile oil based on saturation functions • Below the OWC ECLIPSE finds some immobile oil • Below the OWC there is really only residual oil • Eclipse overestimates the immobile oil • The mobile oil is then underestimated • The mobile fluid correction compensates for this effect Sw=(1-SOWCR) OWC Sw Depth C B A DWater zone Transition zone Mobile fluid correction requires RUNSPEC EQLOPTS ’MOBILE’ / Sw=SWL E
- 301. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 301 of 499 08/04/99 Mobile Fluid Correction Consider a cell intersecting the OWC, with the cell centre above the contact, as in Figure 98. ECLIPSE assigns saturations at the cell centre i.e. the fact that part of the cell is below the OWC is ignored. So, when the amount of mobile oil in the cell is calculated, ECLIPSE assumes by default that the portion of the cell below the OWC contains mobile oil, as does the rest of the cell. The default calculation is as follows. The pore volume is DCBAV +++= EQ. 52 Where A+B is the oil volume C+D is the water volume The oil in place is A+B and the oil saturation is V BA So + = EQ. 53 The immobile oil saturation is calculated by lookup from the saturation tables as V CB SOWCR + =−1 EQ. 54 Which ignores the fact that area C lies below the OWC. The mobile oil saturation Somob is So-(1-SOWCR) i.e. V CB V BA Somob + − + = EQ. 55 Or V CA Somob − = EQ. 56 But the correct mobile oil saturation is A/V. Hence the fine scale equilibration options produce underestimates of the initial mobile OIP although the fluids in place estimate is comparatively accurate.
- 302. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 302 of 499 08/04/99 To calculate the correct sweep for cells intersecting the OWC, ECLIPSE uses a facility based on endpoint scaling, which operates by calculating the mobile and critical phase saturation for each sub-cell. The cell mobile phase saturation is determined and the cell critical saturation is modified such that the correct sweep is preserved. A more detailed description can be found in the ECLIPSE 100 TECHNICAL APPENDICES in the section on SATURATION TABLE SCALING. Keyword Usage The mobile fluid correction is activated using the ‘MOBILE’ switch in the EQLOPTS keyword in RUNSPEC. It is only relevant if fine grid equilibration is also active.
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- 304. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 304 of 499 08/04/99 Transition Zone Endpoint Variation Figure 99: Transition Zone Endpoint Variation • The depth at which dry oil is taken is often known accurately • Water is immobile at shallower depths • This is implemented by setting a threshold saturation • If the saturation is less than the threshold, the critical saturation is set equal to the phase saturation • If the saturation is greater than the threshold, it is unchanged • The overall effect is to immobilise phases up to a certain threshold saturation Sw Swcr Swco Default behavour Behavour with TZONE To activate water "freezing" use TZONE --Oil Water Gas F T F / in the PROPS section
- 305. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 305 of 499 08/04/99 Transition Zone Endpoint Variation In some reservoirs the phase saturation needs to be initially immobile provided it is less than a certain threshold value. Endpoint scaling could be used to implement this (see the ENPTVD keyword). It is, however, more convenient to set a constant critical saturation with depth and alter the critical phase saturation of individual cells, regardless of phase mobility. This also has the advantage of allocating the correct initial mobile fluid in place. The facility is invoked using the TZONE keyword in the PROPS section, Keyword Usage The TZONE keyword syntax is TZONE --1 2 3 --OIL WATER GAS The values of each item should be set to T or F to activate or deactivate the facility.
- 306. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 306 of 499 08/04/99 Matching Initial Water Distribution Figure 100: Matching Initial Water Distribution • OIP depends very strongly on initial water distribution • The default ECLIPSE initialisation gives abrupt variations in water saturation • Actual water saturation distribution with height is often smooth • SWATINIT can be used to set initial water saturations on a cell-by-cell basis • SWATINIT is used in the PROPS section Depth Eclipse Initial Sw Observed Initial Sw GOC Free Water Level Above OWC Sw=SWL from sat fns Depth Below OWC Sw=SWU from sat fns Above OWC Sw varies smoothly Define Sw using SWATINIT array in PROPS section Below OWC Sw=SWU from sat fns TZ Top
- 307. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 307 of 499 08/04/99 Matching Initial Water Distribution The initial water saturation distribution is one of the most significant factors in determining the OIP. A water saturation distribution is often known from direct measurement by open hole logs and/or other downhole methods. Capillary pressure, on the other hand, is often more difficult to estimate accurately enough to yield consistency with observed water saturation. ECLIPSE provides a facility for adjustment of capillary pressure in order to honour an initial water saturation distribution. The initial cell water saturation is input using SWATINIT in the PROPS section and ECLIPSE applies endpoint scaling to the capillary pressure curves as required to stabilise the water. There are, however, some limitations to the function of SWATINIT: • Water saturation values that cannot be honoured because they are below the contact will be overwritten with SWU when ECLIPSE later equilibrates the simulation. Pc=0 below the contact, so Sw=1 there also. • If a cell is given a saturation corresponding to zero capillary pressure then the Pc curve is left unscaled • If SWATINIT is not greater than the connate water saturation then the capillary pressure is left unscaled. • The SWATINIT saturation may not be honoured exactly if fine grid equilibration is in use.
- 308. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 308 of 499 08/04/99 Enumeration Figure 101: Initial conditions defined by enumeration • Initial conditions my be set explicitly • The initial pressures must be set for each cell • Initial saturation of each active phase, except oil must be set in each cell • Initial solution ratios (Rs and / or Rv) must be defined in each cell. • Capillary pressure and phase saturation must be consistent to ensure stable initial conditions • All other relevant solution variables must also be specified, such as tracer concentration. • Enumeration may be appropriate in reservoirs with initially tilted contacts or non- equilibrium situations. Phase Combination Enumeration Keywords OIL, GAS, DISGAS, WATER PRESSURE, SWAT, SGAS, RS OIL, GAS, DISGAS PRESSURE, SGAS, RS OIL, WATER PRESSURE, SWAT OIL, GAS PRESSURE, SGAS GAS, OIL, VAPOIL PRESSURE, SGAS, RV GAS, OIL, VAPOIL, WATER PRESSURE, SGAS, SWAT, RV GAS, WATER PRESSURE, SGAS, SWAT OIL, GAS, VAPOIL, WATER PRESSURE, SGAS, SWAT, RV OIL PRESSURE GAS PRESSURE, SGAS WATER PRESSURE, SWAT
- 309. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 309 of 499 08/04/99 Enumeration As an alternative to equilibration, the initial conditions may be specified explicitly for every grid cell if the available data is sufficient in quantity and quality. Once the phase options have been chosen in the RUNPSEC section, enough data must be provided to calculate the initial solution for each phase. Data checks carried out by ECLIPSE ensure that this is done. The full list of keywords used in the SOLUTION section for enumeration is: PRESSURE, SWAT, SGAS, RS, RV. As an alternative to PRESSURE on a cell-by-cell basis, the pressure can be specified as a function of depth using PRVD. Oil saturation is calculated from gas and water saturation. The necessary keywords for each phase combination are listed in Figure 101. If one of the keywords is specified, all must be specified. It is not possible to, for instance, specify the saturations and expect ECLIPSE to calculate the pressure. Enumeration is not appropriate for input data of poor or inconsistent quality. As an example, consider the initial water saturation distribution. This may be estimated by downhole sampling of water saturation in all the reservoir formations and subsequently either extrapolated to create maps, or a bespoke correlation may be calculated to generate the initial Sw. throughout the reservoir. The capillary pressures must be consistent with the water saturations or else the initial solution will not be stable. Since, however, the water saturation is measured at a relatively small scale and extrapolated to reservoir scale, the capillary pressures must be subject to the same upscaling process. This may be very difficult and once completed, any adjustment of initial water saturation in the interests of history matching would be followed by adjustment of the upscaled capillary pressures.
- 310. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 310 of 499 08/04/99 Initial Solution Ratios Figure 102: Initial solution ratios • Dissolved gas concentration, Rs or its depth variation i.e. RS or RSVD • Vaporised oil concentration, Rv or its depth variation i.e RV or RVVD • Bubble point and / or dew point depth variation i.e. PBVD and/or PDVD Pb at Rs=0.77Pb at Rs=0.241 Bo µo PVTO --Rs Pb Bo µo 0.13700 1214.70 1.17200 1.97000 / 0.19500 1414.70 1.20000 1.55600 / 0.24100 1614.70 1.22100 1.39700 / 0.28800 1814.70 1.24200 1.28000 / 0.37500 2214.70 1.27800 1.09500 / 0.46500 2614.70 1.32000 0.96700 / 0.55800 3014.70 1.36000 0.84800 / 0.66100 3414.70 1.40200 0.76200 / 0.77000 3814.70 1.44700 0.69100 / 4214.70 1.44050 1* / 4614.70 1.43400 0.69700 / / Depth Pressure GOC Pg Po Pb Pd
- 311. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 311 of 499 08/04/99 Initial Solution Ratios The initial solution ratios are required as part of the equation of state for the oil and gas phases. Density calculation is impossible without them. They may be specified either on a cell by cell basis using either or both of the following, depending on which phases are active: RS, the solution gas-oil ratio RV, the vaporised oil-gas ratio The same information may be entered as a function of depth using either or both of RSVD and RVVD. These are tables of solution gas-oil ration and vaporised oil-gas ratio versus depth. One of either or both is needed for each equilibration region. As an alternative to RSVD and RVVD the bubble point and dew point variation with depth may be set using PBVD and PDVD. One of either or both is required for each equilibration region. NOTE that if RSVD or PBVD is not specified in a model where it is applicable, the datum depth in the first item of EQUIL must be the depth of the GOC. In this case the undersaturated GOR is set to the saturated value at the GOC by PVT table interpolation. NOTE also that if RVVD or PDVD is not specified in a model where it is applicable, the datum depth in the first item of EQUIL must be the depth of the GOC. In this case the undersaturated GOR is set to the saturated value at the GOC by PVT table interpolation
- 312. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 312 of 499 08/04/99 Restarts Figure 103: History matching restart runs • A restart run uses the output from a previous simulation to define the initial conditions • The restart file from one simulation is read to define the initial solution in another simulation • Restarts are similar to enumeration inasmuch as the solution variables are set for each cell. • Restart file output contains a complete description of the state of the simulation at the time of output, with some exceptions, notably VFP curves. Prediction PeriodHistory Period Restart RunBase Run Present day Time Field production rate
- 313. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 313 of 499 08/04/99 Restarts The purpose of a restart is to begin a simulation at any specified time without repeating earlier simulations whose results are already known. The successful conclusion of a history match is not necessarily at the present day. A number of simulations may be run to examine subsuquent production. There is no point in repeating the computational steps of the history match because the answer is always the same. Using restart files then becomes a means of reducing computing overheads. Usually, a restart file is written at the end of the history match and used as a starting point for simulations of subsequent production scenarios. ECLIPSE restart files contain a complete description of the simulation at the time of output. This includes pressure, saturation and solution ratios for each grid cell as well as • surface facilities such as pipelines and separators • wellhead locations, completion locations and definitions • flow rate targets and As a rule, all available information is written to the restart file. The exceptions to this rule are: • Flow correlations in the form a of VFP curves (VFPPROD, VFPINJ) • Reporting instructions (RPTSCHED, RPTRST) • Any section keywords (COLUMNS, DEBUG, ECHO, EXTRAPMS, FORMFEED, INCLUDE, MESSAGES, NOECHO, NOWARN and OPTIONS) • Annual scheduling files used in the ECLIPSE 200 Gas Field Operations Model (GASBEGIN, GASEND and any keywords in between) • Keywords for the ECLIPSE 200 Reservoir Coupling option (SLAVES, DUMPCUPL, and USECUPL) • Well PI scaling tables (PIMULTAB) ECLIPSE has facilities to read the contents of a restart file and continue simulating from the date of the restart file. There are two ways to do this, known as full and fast restarts, respectively. • A fast restart reads the RUNPSEC, GRID, EDIT, PROPS and REGIONS sections from a SAVE file. The SAVE file is generated during the history match and is in coded form so that, for instance, transmissibilities do not have to be recalculated. The RPTSCHED
- 314. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 314 of 499 08/04/99 or RPTRST keywords should also be used to request output of a restart file at the end of the history match. • A full or flexible restart reads a complete data file, which is a modified copy of the history match data file. Restart runs are often used to model distinct stages of field development during the prediction phase. The restart run is not necessarily a prediction model. For instance, a history match may be performed in several phases, each restarting from a previous match. For this reason the model that generates a restart file is usually called the base case, the model that uses the restart file is called the restart run. Figure 104: Multiple restarts during prediction Time Field production rate Prediction Rest 1 Rest 2 Rest 3Base Rejected prediction scenarios History
- 315. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 315 of 499 08/04/99 How to Create a Full Restart Run Figure 105: Steps in creating a full restart run • Ensure that a restart file is written at the conclusion of the history match. Suppose the history match dataset is named HIST.DATA • Choose a date from which to restart the simulation and ensure that a restart file is output at that date by using RPTSCHED or RPTRST. Run the simulation. Examine the PRT file at that date and note the sequence number of the restart file written. If the sequence number is, say, ten, then restart file number ten is required, i.e. HIST.X0010. • Copy HIST.DATA to the prediction dataset, say PRED.DATA • In PRED.DATA remove or comment out the EQUIL keyword and all the aquifer information from the SOLUTION section. • In PRED.DATA insert the following in the SOLUTION section RESTART –-Root Sequence é Ensure a restart is written by Eclipse at the chosen date. Use RPTSCHED and/or RPTRST é Check output dates in the PRT file é Copy the base case to the restart data file é In the restart replace equilibration and aquifers with RESTART é Insert SKIPREST in the SCHEDULe section. Alternatively, delete timestepping keywod up to the restart date. é Keep VFP tables é Add more timestepping keywords
- 316. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 316 of 499 08/04/99 -- number HIST 10 / • In PRED.DATA insert the keyword SKIPREST in the SCHEDULE section immediately after any VFP tables, if any, and in any case before the well definition keywords. Alternatively, delete or comment out all keywords up to the date of the restart, except for VFPPROD and VPFINJ, if they are present. The SKIPREST keyword instructs ECLIPSE to ignore any simulator advance and well definition and control keywords up to the time of the restart. • Extend the simulation into the future by adding extra DATES and/or TSTEP keywords before the END keyword. This will provide a base prediction, i.e. a model in which the well controls are the same as those in force at the end of the history match. Run PRED.DATA. How to Create a Fast Restart Run Figure 106: Steps in creating a fast restart é Ensure a restart is written by Eclipse at the chosen date. Use RPTSCHED and/or RPTRST é Check output dates in the PRT file é Copy the base case to the restart data file é In the restart delete everything up to the SUMMARY or SCHEDULE keyword é Insert LOAD and RESTART keywords é Insert optional SUMMARY section é Insert SKIPREST in the SCHEDULE section. Alternatively, delete timestepping keyword up to the restart date. é Keep VFP tables é Add more timestepping keywords
- 317. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 317 of 499 08/04/99 • Ensure that a SAVE file is written by the base run. The SAVE keyword in the GRID section of HIST.DATA generates the SAVE file, named HIST.SAVE. This file contains the contents of the RUNSPEC to SOLUTION sections of HIST.DATA inclusive, in coded form. For the sake of argument, suppose the history match dataset is named HIST.DATA • Choose a date from which to restart the simulation and ensure that a restart file is output at that date by using RPTSCHED or RPTRST. Run the simulation. Examine the PRT file at that date and note the sequence number of the restart file written. Say it is restart file number ten, i.e. HIST.X0010. • Copy HIST.DATA to PRED.DATA. Delete everything from PRED.DATA up to the SUMMARY keyword. If there is no SUMMARY section, delete everything up to the SCHEDULE keyword. • Insert the following at the beginning of PRED.DATA LOAD HIST / RESTART HIST 10 / • Insert the keyword SKIPREST in the SCHEDULE section of PRED.DATA immediately after any VFP tables, if any, and in any case before the well definition keywords. Alternatively, delete or comment out all keywords up to the date of the restart, except for VFPPROD and VPFINJ, if they are present. The SKIPREST keyword instructs ECLIPSE to ignore any simulator advance and well definition and control keywords up to the time of the restart. • Extend the simulation into the future by adding extra TSTEP and/or DATES keywords before the END keyword. This will provide a base prediction, i.e. a model in which the well controls are the same as those in force at the end of the history match. Run PRED.DATA. Flexible vs. Fast Restarts Fast and flexible restarts have their respective advantages and disadvantages. The following comments may be of use. • A fast restart uses the same RUNSPEC switches and options as base case. If extra options are to be used in the restart run, the RUNSPEC section of the base case should be changed to ensure enough memory is allocated. For instance, if infill wells are to
- 318. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 318 of 499 08/04/99 be drilled, the WELLDIMS keyword in the base case dataset should allow for enough of them • The input and output styles of a fast restart run are the same as for the base case. This is likely to cause inconvenience if the output styles are different: the restart run will not be able to read output from the base run by default. Users should take case to ensure that the input and output styles are the same for base case and restart runs. Refer to the @convert macro in the section “Utility Macros”, p.66 for more information. • Note that the most direct way to tell at what simulation date a restart file was written is to read the .PRT or .LOG file. • The time taken by ECLIPSE to process the RUNSPEC to REGIONS sections of a data file is usually a small part of the time taken to run a simulation. Using a fast restart will reduce the computing overhead significantly only in the most large and complex of models. • It is much easier to use SKIPREST in the SCHEDULE section instead of deleting or commenting out keywords by hand.
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- 320. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 320 of 499 08/04/99 Output Control Figure 107: SOLUTION section output control • RPTSOL is the only SOLUTION section output control keyword • A full listing of available SOLUTION section keywords can be found in the ECLIPSE 100 REFERENCE MANUAL RPTSOL ’SOIL’ ’EQUIL’ ’RESTART=2’ / Tabular and printed data in the PRT file Initial conditions in the restart file
- 321. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 321 of 499 08/04/99 Output Control The sole output control keyword used specifically in the SOLUTION section is RPTSOL. Output is to the PRT file (or LOG file) as well as to a restart file. It takes two types of argument The pre-96a format uses a series of integers and multiple default values. From ECLIPSE version 96a the arguments may take the form of mnemonics enclosed in quotes. For instance RPTSOL ‘PRES’ ‘RV’ ‘RESTART=2’ ‘EQUIL’ / is equivalent to RPTSOL 1 4* 1 2 1* 1 / The pre-96a format is compatible with subsequent releases of ECLIPSE. All the RPTSOL parameters direct output to the PRT file and then LOG file if the simulation is running in the background, except for the 7th switch or RESTART mnemonic. If this is set to at least 1 or the mnemonic ‘RESTART=2’ is used, ECLIPSE outputs a restart files containing the initial conditions, provided the simulation has been advanced by at least one timestep. If the output is multiple, this file has the extension .X0000 or .A0000, otherwise it has the suffix .UNRST or .FUNRST as normal.
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- 324. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 324 of 499 08/04/99 Aquifer Modelling Facilities Figure 108: Aquifer definition • Aquifers can be modelled as numerical, analytical, grid or flux aquifers. • Grid and numerical aquifers are specified in the GRID section • Any grid or numerical aquifer NNCs are specified in the GRID section • Analytical and flux aquifers are specified in the SOLUTION section • Analytical aquifer NNCs are also specified in the SOLUTION section. • Different aquifer types may be used in a model but Carter-Tracy and Fetkovich aquifers cannot be used in the same model. • The number of aquifers and the maximum number of cells to which they are connected is specified in AQUDIMS in the RUNSPEC section. Grid Cell Aquifers Numerical Aquifers Analytical Aquifers: Fetkovich Carter-Tracy Flux Aquifers
- 325. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 325 of 499 08/04/99 Aquifer Modelling Facilities There are several ways to specify aquifers in ECLIPSE: • As a grid cell aquifer. To do this: - • Choose cells beneath the OWC to function as an aquifer • Multiply their pore volume as necessary using MULTPV. • Input any extra connections to the oil and/or gas zone with explicit NNCs using the NNC keyword. • As a numerical aquifer. To do this: - • Nominate a number of grid cells, using the keyword AQUNUM, to function as an aquifer • Input the NNCs to the reservoir using AQUCON. • As an analytical aquifer. To do this: - • Create an aquifer using keywords ACUCT (Carter-Tracy aquifer) or AQUFET or AQUFETP (Fetkovich aquifer) • Join them to the reservoir using the AQUANCON keyword. • As a flux aquifer. To do this: - • Create an aquifer of constant flux per unit area using the AQUFLUX keyword • Join it to the reservoir grid by NNCs defined in the AQUANCON keyword. NOTE that aquifers connected to cells above the OWC will flow into the oil zone. In numerical aquifers this takes place because the interblock mobility is taken from the upstream (aquifer) cell, not the downstream cell in which the water relative permeability may be zero. Analytical aquifer flow is independent of relative permeability.
- 326. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 326 of 499 08/04/99 Grid Cell Aquifers Figure 109: Grid cell aquifer definition • Cells in the water leg of the simulation grid are used as an aquifer • Grid cell aquifers are defined in the GRID and/or EDIT sections. • Pore volume multipliers may be applied and their properties altered in the GRID and/or EDIT sections. • Cell pressure can be reported during the run. • The aquifer will behave like a finite aquifer by default. K=1 BOX --I1 I2 J1 J2 K1 K2 1 1 2 8 1 1 / EQUALS ’MULTPV’ 10000 / / ENDBOX J I Grid aquifer cells Oil zone Inactive cells
- 327. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 327 of 499 08/04/99 Grid Cell Aquifers Aquifers can be incorporated directly into the simulation grid in a number of ways but the method has a number of limitations. The simulation grid can be extended artificially below the OWC. This is a valid approach when modelling aquifers that are small compared to the oil zone. This has the flexibility that goes with the usage of the entire suite of GRID section keywords to modify the aquifer properties to match the simulation to the measured aquifer characteristics. The major disadvantage is that the phase pressures, saturations and solution ratios are solved in the extra aquifer cells as for any other cell, which may dramatically increase the run time if the aquifer contains many cells. In principle aquifers much larger than the oil zone may be defined by multiplying the pore volumes of the water zone cells. The disadvantages of this approach are • Throughput-related convergence problems are likely to occur if an aquifer cell pore volume is more than three orders of magnitude greater than the pore volume of any of its neighbours. • A great deal of time and effort has to be spent in designing a grid to represent the aquifer.
- 328. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 328 of 499 08/04/99 Numerical Aquifers Figure 110: Numerical aquifer definition • Several redundant cells or cells below the OWC are nominated as aquifer cells • Numerical aquifers are defined in the GRID section. • The cell properties are modified by the AQUNUM keyword • Cells are attached to the oil zone by NNCs defined in the AQUCON keyword • The number of numerical aquifers and NNC is defined in AQUDIMS in RUNSPEC K=1 GRID AQUNUM --1 2 3 4 5 6 7 8 9 10 11 12 --Aquifer I J K Area Length φ K Depth Initial PVT SAT --Id pressure table table 1 8 9 1 1E2 1E2 1 / 1 9 9 1 1E4 1E3 1 / 1 10 9 1 1E6 1E4 1 / / AQUCON --1 2 3 4 5 6 7 8 9 10 11 --Aquifer I1 I2 J1 J2 K1 K2 Face Trans Trans Connection --Id mult option option 1 1 1 2 8 1 1 ’I-’ / / J I Numerical aquifer cells Oil zone Inactive cells NNCs to Oil Zone
- 329. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 329 of 499 08/04/99 Numerical Aquifers The user is free to select a number of cells to function as an aquifer. In Figure 110 cells (8-10, 9, 1) have been nominated. They are joined to one another and the reservoir in the order of entry in the AQUNUM keyword and form a single aquifer. The order of connections is (10, 9, 1) flows into (9, 9, 1) (9, 9, 1) flows into (8, 9, 1) (8, 9, 1) flows into the reservoir. The AQUNUM keyword automatically sets zero transmissibility multipliers between the chosen aquifer cells and their neighbours in the grid to prevent unwanted flows into adjacent portions of the grid. Note that aquifer cells cannot be deactivated by keywords including ACTNUM and MINPV. The cell properties including dimensions, depth, porosity, permeability and regions definitions are unaltered by default. Despite the fact that these and other quantities are set using AQUNUM, they must still be defined elsewhere with the standard GRID and REGIONS section keywords. The choice of cell dimensions is significant. In Figure 110, cell pore volumes increase progressively from the oil zone to cell (10, 8, 1) by a factor no greater than 103 between connected cells. This is intended to minimise throughput-related convergence problems. It is often recommended to place an extra row of cells to act as a buffer between the aquifer itself and the oil zone for the same reason. This is unnecessary if the aquifer has been designed to minimise throughput-related convergence problems from the outset. The initial aquifer pressure is usually defaulted to ensure it is in hydrostatic equilibrium with the rest of the simulation grid after initialisation. Instability may nevertheless arise. Consider Figure 111. The OWC is at a depth, which does not coincide with a cell centre depth. The attached aquifer is joined to the entire lateral faces of several cells. There is a difference between the OWC depth and the aquifer depth, i.e. a hydrostatic pressure difference between the aquifer and oil zone. Water will flow into the reservoir from the aquifer in the absence of injection and production and the reservoir pressure will drop until equilibrium is reached. Although this is normally a very minor effect since the height difference is small, users are strongly recommended to design reservoir grids to avoid this. The effect may become very significant if: • A large number of aquifer cells are connected to the oil zone
- 330. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 330 of 499 08/04/99 • The grid cells are large • The initial aquifer pressure is not defaulted and is significantly different from the pressure at the OWC. Figure 111: Model instability from poor aquifer design The effect is not restricted to numerical aquifers. The oil zone-aquifer NNCs are defined using AQUCON. Non-neighbour connections must be enabled and the RUNSPEC NONNC keyword should not be used. The transmissibility between cell (8, 8, 1) and the rest of the reservoir is defined according to the rules outlined in an earlier section on Cartesian grid transmissibility and is defined as: gridaq TTT 111 += EQ. 57 where aq aqaq aq l Ak T 2 = OWC Hydrostatic pressure difference (ρw -ρo )gh
- 331. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 331 of 499 08/04/99 EQ. 58 Where kaq, Aaq and laq are the permeability, cross-sectional area and length, respectively, of cell (8, 8, 1) and Tgrid is calculated as usual. Transmissibility multipliers may be applied to these connections in the 9th item of AQUCON. Item 8 of AQUCON specifies which face of cell (8, 8, 1) is joined to the aquifer. The options are I+, I-, J+, J-, K+ and K- which represent the direction of increasing and decreasing I, J, and K index, respectively. In Figure 110 the I- face of any cell is at the left and I+ face is at the right. The connection option in item 11 determines whether aquifers are permitted to connect to cell faces that are already joined to other active cells. The default is ‘NO’. The alternative is used in hydrogeological modelling to allow aquifers to be joined to the interiors of simulation grids in simulations of groundwater propagation within fractures of insignificant size compared to the grid cells.
- 332. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 332 of 499 08/04/99 Fetkovich Aquifers Figure 112: Fetkovich aquifer definition • Fetkovich aquifers are defined in the SOLUTION section. • The aquifer properties are defined by the AQFET or AQUFETP keywords • Fetkovich aquifers are attached to the oil zone by NNCs defined in the AQUANCON keyword • The total number of analytical aquifers and aquifer NNCs is defined in AQUDIMS in RUNSPEC • Fetkovich and Carter-Tracy aquifers cannot be used in the same run ( )aiiaiwwi hhgPPJQ −+−= (ρα The aquifer inflow is: From material balance the aquifer pressure response is ( )aawta PPVCW −= 00 Integrating these gives Define Fetkovich Aquifers with RUNSPEC AQUDIMS SOLUTION AQUFET --or AQUFETP AQUANCON ( )( ) ( ) ∆− ∆−− −+−= 0 0 exp1 wt wt aiiaiai VC tJ VC tJ hhgPPJQ ρα
- 333. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 333 of 499 08/04/99 Fetkovich Aquifers Fetkovich aquifers are based on a pseudo-steady state productivity index and material balance between aquifer pressure and cumulative influx. The flow is modelled by the equations in Figure 112 where the subscripts a and i denote the aquifer and grid cell i, respectively. Qai is the inflow rate from aquifer to cell i Jw is the aquifer productivity index; αi is the area fraction for cell i; Pa is the aquifer pressure at time t Pi is the cell pressure at time t ρ is the aquifer water density hi and ha the cell depth and aquifer datum depth, respectively Wai is the cumulative influx from aquifer to cell i. Ct is the total aquifer compressibility Vw0 is the initial aquifer volume Pa0 is the initial aquifer pressure The aquifer flow in Figure 112 is very similar to the familiar well inflow performance equation. The relationship of aquifer to reservoir is very similar to the relationship of reservoir to well. Solution of the radial diffusivity equation in which the well is treated like a reservoir whilst the reservoir is treated like an aquifer provides results analogous to the familiar results obtained for wells. The consequence is that, given the same boundary conditions, the aquifer PI is virtually identical in form to a well PI. Fetkovich aquifers can effectively represent a wide range of aquifer types from the steady state infinite aquifer which provides constant pressure support to the “pot” aquifer, which is small compared to the reservoir and whose behaviour is determined by the reservoir influx. If the aquifer has a large time constant, it responds slowly to variations in reservoir pressure and the behaviour approaches that of a steady state aquifer. If the PI is large so that the time constant is small, the behaviour approaches that of a “pot” aquifer which is close to pressure equilibrium with the reservoir at all times. The topic is also discussed in the ECLIPSE 100 TECHNICAL APPENDICES. Fetkovich aquifers can be specified using in two ways AQUFET is used to specify a single aquifer connected to one reservoir face: AQUFET --1 2 3 4 5 6
- 334. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 334 of 499 08/04/99 --Datum Initial Initial rock+ PI PVTW --depth pressure volume water table -- @ datum compressibility No. --7 8 9 10 11 12 13 14 --I1 I2 J1 J2 K1 K2 Face Initial -- Salt concn AQUFETP and AQUANCON are used to specify multiple Fetkovich aquifers and/or aquifers connected to more than one reservoir face. AQUFETP --1 2 3 4 5 6 --Id Datum Initial Initial rock+ PI -- depth pressure volume water -- @ datum compressibility --7 8 --PVTW Initial --table No. Salt concn AQUANCON --1 2 3 4 5 6 7 8 9 --Id I1 I2 J1 J2 K1 K2 Face Influx -- coefficient --10 11 --Influx Connection --coefficient option --multiplier AQUFETP is followed by up to NANAQU records of analytical aquifer data, where NANAQU is defined in AQUDIMS in the RUNSPEC section. Refer to the section titled Numerical Aquifers for a discussion on the individual items in each record. AQUANCON specifies the connection data for the aquifer(s). The items that are common to the AQUCON keyword are discussed in the section on Numerical Aquifers. The aquifer influx coefficient determines the total communication between the aquifer and cells to
- 335. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 335 of 499 08/04/99 which it is joined. The default for each cell is its face area. The influx coefficient multiplier may be applied to the influx coefficient of each aquifer-cell connection.
- 336. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 336 of 499 08/04/99 Carter-Tracy Aquifers Figure 113: Carter-Tracy aquifer definition • Carter-Tracy aquifers are defined in the SOLUTION section. • The aquifer properties are defined by the AQCT keyword • The pressure response is defined by an influence function, which may be entered with the AQUTAB keyword. • Carter-Tracy aquifers are attached to the oil zone by NNCs defined in the AQUANCON keyword • The total number of analytical aquifers and aquifer NNCs is defined in AQUDIMS in RUNSPEC • Fetkovich and Carter-Tracy aquifers cannot be used in the same run a tw c kc rC T 1 2 0φµ = The main parameters governing Carter-Tracy aquifer behaviour are the time constant Tc , which is t/tD , and the aquifer influx constant β. 2 02 rChc tθφβ = The pressure drop at the aquifer boundary is )(0 DD a a tP Q PP β =− ( ) ( )[ ]{ }tPittPibaQ iai −∆+−=α and the average flow rate to cell i from time t to t+∆t is To define Carter-Tracy aquifers use RUNSPEC AQUDIMS SOLUTION AQUCT AQUTAB AQUANCON Influence Function
- 337. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 337 of 499 08/04/99 Carter-Tracy Aquifers Carter-Tracy aquifers use tables of dimensionless time td versus dimensionless pressure Pd(td)to determine the amount of influx. The model approximates a fully transient model. Limiting cases of the Carter-Tracy aquifer model can represent steady state or “pot” aquifers. It has the advantage that intermediate behaviour can also be simulated, i.e. an aquifer which behaves as a steady state aquifer at first but gradually approaches the behaviour of a “pot” aquifer. The flow is modelled by the equations in Figure 113, where ka is the aquifer permeability φ is the aquifer porosity µw is aquifer water viscosity Ct is the total aquifer compressibility r0 is the aquifer inner radius (or reservoir outer radius) c1, c2 are constants h is aquifer thickness θ is the angle subtended by the aquifer boundary to the centre of the reservoir (the influence angle) Qa is aquifer flow rate Pa0 is the initial aquifer pressure P is the average water pressure at the aquifer/reservoir boundary αi is the area fraction tD and PD are dimensionless time and pressure, respectively a, b are functions of time, β, Tc, dimensionless pressure. The topic is discussed in more detail in the ECLIPSE 100 TECHNICAL APPENDICES. Carter-Tracy aquifers are specified using AQUCT, AQUTAB and AQUANCON. AQUCT --1 2 3 4 5 6 7 --Id Datum Initial K φ rock+ External -- depth pressure water radius -- @ datum comp. --8 9 10 11 12 --Thickness Influence PVTW Influence Initial -- angle table No. fn table No. salt concn
- 338. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 338 of 499 08/04/99 The radius is the external radius of the reservoir, or the internal radius of the aquifer. The influence angle is the angle subtended by the aquifer at the aquifer-reservoir boundary. Item 11 is a pointer (default value 1) to an influence function defined in AQUTAB. AQUTAB consists of columns of dimensionless time and dimensionless pressure. Table number 1 is the default and cannot be altered by the user. It represents a constant rate terminal aquifer as given by van Everdingen and Hurst.
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- 340. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 340 of 499 08/04/99 Flux Aquifers Figure 114: Flux aquifer definition • Flux aquifers are defined in the SOLUTION section. • The aquifer has no properties as such • The flow rate is specified directly by the user. It may be negative, representing flux out of the reservoir. • As regards the RUNSPEC section, flux aquifers are treated the same as analytical aquifers. • Flux aquifers are defined using AQUFLUX • Connections to the reservoir are created using AQUANCON. • Flux aquifers cannot be used with the AQUFET keyword. iiaai mAFQ = A constant flux aquifer has water flow To define a flux aquifer use RUNSPEC AQUDIMS SOLUTION AQUFLUX AQUANCON SCHEDULE AQUFLUX
- 341. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 341 of 499 08/04/99 Flux Aquifers The water flow Qai into grid cell i from a flux aquifer is as shown in Figure 114 where Fa is the flux Ai the area of the connecting cell block, from the cell geometry mi is an aquifer influx multiplier. The AQUFLUX keyword contains up to NANAQU records of data, each consisting of an aquifer identification number and the flux. The flux can be modified during the simulation by re-entering AQUFLUX in the SCHEDULE section.
- 342. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 342 of 499 08/04/99 Output Control Figure 115: Output control • Summary quantities are requested in the normal manner • RPTGRID can output numerical aquifer definitions and NNCs. • RPTSCHED can output Fetkovich or Carter-Tracy aquifer status • RPTSOL can output analytic aquifer data and individual connection data Summary Quantities AAQR, FAQR, FAQT, AAQT, AAQP Print file Data RPTGRID, RPTSCHED, RPTSOL
- 343. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 343 of 499 08/04/99 Output Control • The AAQP aquifer pressure summary quantity applies only to Fetkovich aquifers • Other SUMMARY quantities report instantaneous and cumulative aquifer influxes. • The AQUNUM and AQUCON mnemonics in RPTGRID output numerical aquifer definitions and NNCs, respectively, in tabular form to the PRT file • The AQUCT or AQUFET or AQUFETP mnemonics in RPTSCHED output status reports on Fetkovich or Carter-Tracy aquifers in tabular form to the PRT file. • The AQUFET or AQUFETP or AQUCT or AQUANCON mnemonics of RPTSOL output analytic aquifer data to the PRT file in tabular form. If any of these is set to 2 (e.g. ‘AQUFET=2’) then additional data on the aquifer-grid cell connections is written to the PRT file.
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- 346. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 346 of 499 08/04/99 Purpose of the SUMMARY Section Figure 116: SUMMARY Section Purpose • The SUMMARY section is where output to generate line plots is specified • The data is contained in the summary files • The data may be quantities relating to blocks (grid cells), wells, completions, groups, regions, inter-region quantities or the entire field • Data is requested using simple mnemonics
- 347. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 347 of 499 08/04/99 Purpose of the SUMMARY Section The SUMMARY section is used only to request output of certain simulation results. These are mostly quantities which may be drawn in 2D line plots. The output quantities are specified according to mnemonics made up of four or five characters. The following rules apply to most of the mnemonics but there are some exceptions. All mnemonics in use are listed in the ECLIPSE 100 REFERENCE MANUAL. First character The first character is the main identifier and is one of F Field G Group R Region W Well B Block (i.e. grid cell) C Connection Second character The second character specifies the fluid and is one of O Oil W Water G Gas V Volume at reservoir conditions T Tracer L Liquid i.e. volume at surface conditions Third character The third character specifies the flow type and is one of P Production I Injection F Flow Fourth character The fourth character specifies instantaneous or cumulative flow and is one of R Rate T Total
- 348. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 348 of 499 08/04/99 Fifth character The fifth character is special. L Liquid H History G Gas Some mnemonics that follow the above convention are FOPR Field Oil Production Rate GVPR Group Volume Production Rate RTIT Region Tracer Injection Total WWPT Well Water Production Total BOFT Block Oil Flow Total COFR Connection Oil Flow Rate A few exceptions are: WBHP Well Bottom Hole Pressure FWCT Field Water CuT ROIP Region Oil In Place BPR Block PRessure BOSAT Block Oil SATuration WWCT Well Water Cut BAPI Block API FAQR Field AQuifer Influx Rate FPR Field Average PRessure These each have a history equivalent, available in history matching runs e.g. WBHPH, FWCTH, WWCTH, FPRH etc.
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- 350. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 350 of 499 08/04/99 Additional Parameters Figure 117: Additional SUMMARY mnemonic parameters • SUMMARY section mnemonics take extra parameters depending on what is needed to specify the reported quantity é FIELD quantities take no extra parameters e.g FOPR Field Oil Production Rate é Region quantities associated with inter-region flow take pairs of region numbers e.g. ROFT 1 2 / Region Oil Flow Total between 1 and 2 é Other region quantities take a list of region numbers e.g. RWIP 1 2 3 / Region Water In Place in regions 1, 2, 3. é Group quantities take a list of group names e.g. GVPR ’PLAT-A’ ’PLAT-B’ / Group Voidage Production Rate for PLAT-A and PLAT-B é Well quantities take a list of well names e.g. WTHP ’P11’ ’P21’ ’I20’ / Well Tubing Head Pressure for P11, P21, I20. é Block quantities take a list of grid block I, J, K indices e.g. BGKR 1 1 1 / 1 2 1 / / Block Gas relative permeability for (1,1,1) and (1,2,1) é Connection quantities take a well name and grid block I, J, K indices e.g. COFR ’P21’ 2 1 1 / ’P21’ 2 1 2 / / Connection Oil Flow Rate for (2,1,1) and (2,1,2) in well P21
- 351. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 351 of 499 08/04/99 Additional Parameters Field quantities Field quantities take no additional parameters and require no terminating forward slash. Region quantities Keywords requesting output of flows between regions must be followed by a list of pairs of region numbers. For instance RWFT 1 3 / 2 3 / / requests output of the total water flow between regions 1 & 3, and regions 2 & 3. The final forward slash is significant. Other region quantities can be followed by a list of region numbers. For instance, ROIP 5 7 12 / requests output of the oil in place in regions 5, 7 and 12. Group quantities Group quantities can be followed by a list of group names enclosed in quotes and terminated with a forward slash. A blank list requests output for all groups. As an example GOPR ‘PLAT1’‘PLAT2’ / or GOPR / are equivalent if there are only two groups in the model. Wildcard characters (*) are not permitted as keyword parameters. Well quantities The syntax is the same as for group quantities Block quantities Block quantities are followed by a list of cell I, J, K indices, each line terminated by a forward slash and the list terminated with another forward slash. For instance, BOSAT
- 352. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 352 of 499 08/04/99 1 1 1 / 8 1 5 / 9 12 3 / / Connection quantities Connection quantities are followed by a list of well names in quotes and completion I, J, K indices, each terminated by a forward slash. The list is terminated by another forward slash. For instance, CGOR ‘P1’ 10 1 1 / ‘P2’ 20 1 1 / /
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- 354. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 354 of 499 08/04/99 Output Controls and Additional Keywords Figure 118: SUMMARY section output control keywords • Additional keywords do not always follow the rules for SUMMARY section mnemonics • Anisotropic relative permeability keywords • Reservoir Volumes • Oil Recovery Efficiencies • Oil Recovery Mechanisms • Analytic Aquifer Quantities • Brine Option Keywords • Brine Option Keywords • Simulator Performance Keywords • Output Control Keywords • A full listing of each keyword class can be found in the ECLIPSE 100 REFERENCE MANUAL. Anisotropic relative permeability Reservoir volumes Oil recovery efficiencies Oil recovery mechanisms Analytic aquifer quanities Brine option quantities Simulator performance keywords Output controls
- 355. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 355 of 499 08/04/99 Output Controls and Additional Keywords Anisotropic relative permeability keywords When any of the following options have been enabled in the RUNPSEC section: • Directional relative permeability (‘DIRECT’ in SATOPTS) • Directional endpoint scaling (‘DIRECT’ in ENDSCALE) • Vertical equilibrium (VE) • Two-point upstreaming for miscible flood (‘TWOPOINT’ in MISCIBLE) A number of mnemonics for output of cell oil, water and gas relative permeabilities for each cell face are permitted. An example is BWKRI- for cell water relative permeability in the downstream direction Reservoir Volumes A number of keywords reporting pore volumes at reservoir conditions are available. These include the total pore volume and pore volumes containing the various reservoir fluids. Oil Recovery Efficiencies The oil recovery efficiencies are used as figures of merit for estimation of overall reservoir performance. They include such quantities as (Initial oil in place – current oil in place)/(initial mobile oil w.r.t. water), which provides a measure of the fraction of mobile oil recovered. Oil Recovery Mechanisms The oil recovery mechanism keywords quantify the amounts of stock tank oil produced by rock compaction, water influx, gas influx, oil expansion, solution gas, free gas, traced water and other water influx. Analytic Aquifer Quantities Analytic aquifer quantities are often used to assist in history matching aquifer performance. They are pressure and instantaneous and cumulative rates. Brine Option Keywords Brine option keywords are used in conjunction with the brine tracking option. This option uses tracers to model the progress of water of varying salinity through the
- 356. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 356 of 499 08/04/99 reservoir. An example of its application may be in following the progress of scale- forming agents through the reservoir. Simulator Performance Keywords ECLIPSE advances by a number of discrete timesteps between reporting dates. The progress of the simulation is determined by the convergence tolerances specified by the user. The simulator performance can be estimated by examining the convergence reports in the PRT file but the SUMMARY keywords provide a means of viewing the performance graphically. The most commonly used are • TCPU current CPU usage in seconds • STEPTYPE an integer representing the reason for selecting the timestep length. This may be used to identify the moment of onset of convergence problems. • TIMESTEP the timestep length Output Control Keywords ALL outputs a basic selection of field, group and well data for all wells and groups in use. This is a total of approximately 70 mnemonics and should be used with care if disk space is limited. DATE outputs the date as three quantities: DAY, MONTH, YEAR. RUNSUM outputs the summary data in tabular form at the end of the PRT file. This is output at the conclusion of the simulation run, so if the run is unexpectedly terminated, this will not be produced. SEPARATE outputs tabular summary data to a separate run summary (RSM) file. LOTUS requests output in a format compatible with LotusTM software such as Lotus 1-2- 3. RPTONLY requests output only at reporting times. By default the summary data is written at every timestep. RPTSMRY requests a listing in the PRT file of the keywords used. MONITOR requests output required by GRAF for run-time monitoring NARROW increases the number of columns per page in the RUNSUM output by using narrower columns as in pre-97a versions of the software.
- 357. THE SCHEDULE SECTION– HISTORY MATCHING
- 358. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 358 of 499 08/04/99 Purpose of the SCHEDULE Section Figure 119: SCHEDULE section contents • All of the well data • All of the surface facilities • Fluid flow correlations in tabular form for calculating pressure drops in wells and flow lines • Timestepping and simulator convergence controls • Maximum gas re-solution and oil re-evaporation rates • Reporting controls • Simulation advance and termination keywords
- 359. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 359 of 499 08/04/99 Purpose of the SCHEDULE Section ECLIPSE has very many features relating to well controls and surface facilities. To discuss them all is well beyond the scope of this course. There are approximately sixty different keywords that may be placed in the SCHEDULE section; ECLIPSE 200 options provide more. This course is intended to provide a grounding in the most commonly used features and keywords plus the ability to use the ECLIPSE 100 REFERENCE MANUAL and TECHNICAL APPENDICES as guides to more complex modelling. The SCHEDULE section is used to specify the means of production and injection for the entire model, advance the simulation and specify any other data that depends on time. For example, wells are drilled at a particular time, production and/or injection rates change as time goes on and completions are opened or shut at particular times during the history of the reservoir. These actions must be specified within ECLIPSE at the time they take place. In the other major sections of the ECLIPSE data file the order of keywords is largely unimportant; in the SCHEDULE section it is crucial because the order in which events take place in the field has to be preserved. For instance, the keyword defining wellhead locations must precede the keyword defining the locations and properties of the well connections. The rules on keyword order are too specific to discuss in detail, but in general the order of keywords is the same as the order of events in the production plan. Any restrictions on specific keywords are explained in the ECLIPSE 100 REFERENCE MANUAL. A large part of the contents of the SCHEDULE section is often imported from other applications. For instance, fluid flow correlations are generated in VFPI and included wholesale in the SCHEDULE section. Such applications will not be discussed in any detail although an overview of the data they may provide is included where appropriate.
- 360. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 360 of 499 08/04/99 History Matching Versus Prediction Figure 120: History matching and prediction regimes • History matching and prediction are fundamentally different • The object of history matching is to improve reservoir characterisation. This gives confidence in production estimates made during the later prediction phase • In history matching well rates are known but reservoir characteristics are uncertain • In prediction the reservoir has been characterised but future well rates are simulated. • Workover dates are in general unknown and are performed automatically when production constraints are breached. • History match SCHEDULE sections usually contain detailed well controls over many specific time periods. Workover dates are known and are input at specific times • Prediction SCHEDULE sections usually contain physical and economic constraints on wells and groups applicable for extended periods of production. • Refer to the section titled “The SCHEDULE Section – Prediction”, p.431 for information on keywords specifically used in prediction mode. Reservoir Description Performance Prediction Mathematical model Recovery Mechanism Computer Model Sensitivity Analysis History Match Perfomance depends on quality of reservoir description Interpreted geology, geophysics, petrophysics, production logs, well tests, etc.
- 361. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 361 of 499 08/04/99 History Matching Versus Prediction History Matching During history matching the engineer specifies measured production and injection rates for a reservoir which has been producing for a period of time. Although other reservoir characteristics such as permeability, layering structure, aquifer strength and individual well performance are specified as normal in the remainder of the data file, they are in general uncertain. So, the simulated past performance of the reservoir, that is the well rates calculated by ECLIPSE up to the present day, will in general not correspond to the measured rates specified by the user. History matching then becomes an exercise in identifying those reservoir properties subject to the greatest uncertainty and adjusting them to bring the simulated and measured rates to an acceptable degree of correspondence. History matching is often an iterative process, in which steps are repeated a number of times with variations in reservoir characterisation. There are no precise rules for conducting a history match but the methodology is well known, although it is beyond the scope of this course to discuss it in any detail. Other courses provided by GEOQUEST examine history matching methodology in more detail A schematic example of the SCHEDULE section of a history matching dataset, featuring most of the facilities that may be used during a history match is shown in Figure 121. Prediction Prediction is an exercise in optimising future production and takes one of two forms: • It may follow directly from a history match using the reservoir descriptions estimated during history matching. The history matching and prediction runs may be separate data files. The history match outputs sufficient data in a restart file to continue the simulation into the future. The prediction dataset contains the same reservoir description as the history match but initialises using the restart file output from the history match. • It may predict the production from undrilled structures. In each case the reservoir description used is taken to be the best available. Also, the production controls are different from the history match, with one exception. The base prediction is the continuation of the history match into the future using the well controls
- 362. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 362 of 499 08/04/99 in force at the end of the history matching period. This is the simplest way to run the field since the surface facilities remain unchanged and no workovers take place. Supplementary predictions using a variety of different production strategies are used to improve the oil recovery and reduce production costs. For each prediction case, an aspect of the surface facilities or well management policy is changed and the case is compared to the base prediction. ECLIPSE has a very wide range of well, group and surface facility modelling features and it is likely that several will be invoked during recovery optimisation to model events such as drilling infill wells, modifying facilities constraints and limited access to mobile drilling rigs. The section titled “The SCHEDULE Section – Prediction”, p.431 describes the general structure of the SCHEDULE section of a prediction dataset, featuring many of the facilities within ECLIPSE for prediction mode modelling. Many of the keywords are common to history matching and prediction. The essential keywords that are not explained in the prediction section are described in this section.
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- 364. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 364 of 499 08/04/99 History Match SCHEDULE Section Structure Figure 121: History match dataset structure • The scheme above is general and not all keywords are required • The list is not comprehensive; there are about 60 ECLIPSE 100 SCHEDULE section keywords. The above are most often used in history matching. • Many of the above are also used in prediction mode. • The keywords should be presented in the above order • Some of these are mandatory; some partially duplicate the functions of others; some are not relevant to all types of simulation • Keywords take effect from the date of the previous DATES keyword • The following sections describe the use of each keyword above in turn. Not all keywords are described in exhaustive detail • For further information on keyword structure or technical methods refer to the ECLIPSE 100 REFERENCE MANUAL or ECLIPSE 100 TECHNICAL APPENDICES --VFP tables for pressure reporting VFPPROD, VFPINJ --Well & completion definition WELSPECS, COMPDAT, COMPRP COMPVE --Measured Production and injection rates WCONHIST, WCONINJE, WCONINJ --Simulator control parameters TUNING, TUNINGL, NEXTSTEP --Output control RPTSCHED, RPTRST --Cell GOR &/or OGR increase rates DRSDT, DRVDT --Simulator advance to 1st rate change DATES --Comment separating periods of different flow rate --Manual workovers; PI modification COMPDAT, COMPRP, WELPI WPIMULT --Shut-ins or opening wells WELOPEN --Modified production and injection rates WCONHIST, WCONINJE WELTARG --Simulator control parameters TUNING, TUNINGL, NEXTSTEP --Output control modification RPTSCHED, RPTRST --Simulator advance to second rate change DATES --Comment separating periods of different flow rate --Workovers COMPDAT, COMPRP, WELPI WPIMULT --Shut-ins or opening wells WELOPEN --Modified production and injection rates WCONHIST, WCONINJE WELTARG --Simulator control parameters TUNING, TUNINGL, NEXTSTEP --Simulator advance to third rate change DATES --End of simulation, perhaps at present day END
- 365. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 365 of 499 08/04/99 History Match SCHEDULE Section Structure Figure 121 illustrates the SCHEDULE section structure of a typical history matching dataset. Since the structure of the SCHEDULE section reflects the sequence of events in the field, the details of the structure shown are bound to vary from model to model. Some, however, are mandatory such as the wellhead location and completion specification keywords and should be placed in the SCHEDULE section in the order shown. Keyword order is described here for several keywords and in more detail in the ECLIPSE 100 REFERENCE MANUAL. The keyword sequence shown is intended as a guide to help acquaintance with the major features of the SCHEDULE section. Also, some of the keywords shown have very similar effects to others; one of the alternatives would generally be used, not both. For instance, COMPRP and COMPVE both describe partially penetrated completions but may not be applied to the same well in a given dataset. Likewise, WELPI and WPIMULT are both well productivity or injectivity modifiers. The structure of most keywords in the SCHEDULE section is as follows: KEYWORD <record 1 > / <record 2 > / … … … <record n> / / where each record often refers to an individual well and is terminated by a forward slash. The final forward slash terminates the keyword. All keywords take effect from the end of the previous simulation step. For instance, all of the actions described from the VFPPROD to the DRVDT keyword inclusive in Figure 121 will be in force from the start date in the RUNSPEC section to the beginning of the date specified in the first DATES keyword. Everything specified in that interval remains in force until the end of the simulation unless it is altered at a later stage. So, the actions specified by the COMPDAT to RPTRST keywords between the first and second DATES keywords will only alter some or all of what has gone before. The following sections describe the most commonly used keywords in the order they have been presented in Figure 121, and the mandatory items of these keywords are emphasised. Not every keyword description is comprehensive because detailed write-
- 366. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 366 of 499 08/04/99 ups are available in the ECLIPSE 100 REFERENCE MANUAL. The keyword descriptions are generally supplemented by explanatory material on keyword function and the behaviour of ECLIPSE.
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- 368. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 368 of 499 08/04/99 VFP Curve Specification Figure 122: VFP curve specification • History matching relies on matching observed rates of each flowing phase • Wells are rarely controlled by BHP or THP during a history match • Vertical Flow Performance (VFP) curves represent wellbore fluid flow correlations • For producers VFP curves define the relationship between BHP and THP at a given flow, GOR, OGR, WCT and ALQ • For injectors VFP curves define the relationship between BHP and THP at a given flow and ALQ • Tables of VFP curves are generally used to compare observed and simulated pressures. • VFP tables are created externally to ECLIPSE using a package such as VFPI because they are too complex to create and modify without a pre-processor • Each VFPPROD or VFPINJ keyword is followed by a single table which may be applied to a number of producers or injectors or else pipeline segments --Multidimensional table of BHP vs Flow (e.g. Qo), Water Fraction (e.g. WCT) --Gas Fraction (e.g. GOR), THP and ALQ -- These should NEVER be hand edited VFPPROD 1 7.00000E+03 ’LIQ’ ’WCT’ ’GOR’ / 2.00000E+03 5.00000E+03 1.00000E+04 1.70000E+04 3.00000E+04 / 2.00000E+02 5.00000E+02 1.00000E+03 / 0.00000E+00 2.00000E-01 4.00000E-01 7.00000E-01 9.00000E-01 / 7.70000E-01 1.00000E+00 1.50000E+00 / 0.00000E+00 5.00000E-01 / 1 1 1 1 8.82057E+02 7.76876E+02 1.30267E+03 2.18912E+03 4.20843E+03 / 2 1 1 1 1.25903E+03 1.16634E+03 1.55410E+03 2.53417E+03 4.27927E+03 /
- 369. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 369 of 499 08/04/99 VFP Curve Specification The production of fluids from a well is calculated from the standard inflow performance relationship ( )ghPPPIQ bhpcellpp ρ+−= EQ. 59 where Qp is the phase flow, PIp is the productivity or injectivity of the phase, Pcell the connecting cell pressure, Pbhp the BHP and ρgh the hydrostatic head correction. The lower the BHP, the greater the production, but the amount of fluid that can be drawn up the wellbore decreases as the BHP decreases. Wellbore hydraulics are used during simulation to model that contribution to fluid flow. Vertical Flow Performance (VFP) tables are multidimensional tables of tubing flow properties. They represent the dynamics of fluid flow and are based on correlations. VFP tables are quite general in structure and are used to determine pressure losses in • Wells • Flow lines • Chokes • Pumps • Compressors This can apply to vertical, slanted or horizontal sections of pipe. VFP Table Generation To use the VFPI program the user must specify • The tubing description • The flow correlations used to model the pressure drop • Fluid PVT properties • Fluid flow rates • The pressure at one end of the tubing VFPI is an interactive program written in C++ and is part of the ECLIPSE software suite. VFP correlation generation and VPFI program usage is a subject beyond the scope of this course; only the basic aspects will be covered here. For more detailed information, refer to the VFPI USER GUIDE or approach your local Training Administrator for information on user courses in VFPI.
- 370. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 370 of 499 08/04/99 Production Well VFP Table Structure A production well VFP table consists of BHP versus: • Flow, FLO, of the main produced phase • Tubing head pressure, THP • Water fraction, WFR • Gas fraction, GFR • Artificial Lift Quantity, ALQ. This is commonly used to represent discrete levels of compression or gas lift increments. The water fraction and gas fraction do not necessarily represent water cut and GOR. Their definition depends upon the type of production and production control required. For an oil producer, typically • Flow, FLO = oil rate or liquid rate • Water fraction, WFR = Water Cut, WCT • Gas Fraction, GFR = Gas-oil ratio, GOR or Gas-liquid ratio. If the RSCONST keyword is in use the GFR cannot be gas-liquid ratio. • ALQ = a number representing increments of gas lift or the level of pumping A gas well should have • Flow, FLO = gas rate • Water fraction, WFR = water-gas ratio • Gas fraction, GFR = oil-gas ratio • ALQ = a number representing the degree of compression These tables are entered using the VFPPROD keyword. Each table requires a separate VFPPROD keyword. The table number is contained in the VFPPROD keyword. The WCONPROD, WLIFT and WELTARG keywords assign or reassign the VFP table to a production well. Injection Well VFP Table Structure An injection well VFP table is simpler than a production well VFP table since only one phase is flowing. The injection well VFP table consists of BHP versus • Flow, FLO = phase flow rate • Tubing head pressure, THP. These tables are entered using the VFPINJ keyword. VFPINJ can only enter one table at a time so each table requires a separate VFPINJ keyword The table number is contained
- 371. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 371 of 499 08/04/99 in the VFPPROD keyword. The WCONINJ, WCONINJE and WLIFT keywords assign or reassign the VFP table to an injector. Pipeline Segment VFP Table Structure • If the VFP table refers to part of a production pipeline, it is entered in the ECLIPSE dataset using VFPPROD as usual and is assigned to a pipeline segment using the GRUPNET keyword in the ECLIPSE 200 NETWORKS MODULE • If the VFP table refers to part of an injection network, it is entered in the ECLIPSE dataset using VFPINJ as usual and is assigned to a pipeline segment using the GRUPNET keyword in the ECLIPSE 200 NETWORKS MODULE VFP Table Usage in ECLIPSE Figure 123: VFP table usage in Eclipse The VFP table for an oil producer under THP control represents BHP for a given THP, flow rate, water cut and GOR. This is the set of conditions under which the well may flow. The reservoir, however, must supply fluids at rates compatible with the well flowing conditions. The fluid supply from the reservoir is determined by the inflow performance relationship (IPR). Where this intersects the VFP curves, the fluid can flow from reservoir to wellhead. If the intersection point does not lie on one of the supplied VFP curves, ECLIPSE interpolates linearly between adjacent curves as necessary. This
- 372. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 372 of 499 08/04/99 may, however, arrive at a different THP, which leads to a BHP different from that required by the IPR at the given flow rate. The new BHP affects the IPR since the water cuts and GORs of the open connections will be affected. This in turn requires that a new VFP curve be interpolated from the supplied curves. The solution process is in fact iterative and usually leads to two roots; ECLIPSE will use the root having a higher flow rate. How to Set up VFP Tables in Eclipse • Select the wells to be placed under THP control • Select the flow lines in which pipeline losses are considered significant • Allocate chokes, pumps and compressors to the wells as necessary. • Identify the upper and lower limits of BHP, THP, Q, GFR, WFR and ALQ • Create the tables in VFPI, having gathered the other necessary information • Tabulated VFP curves often converge towards an asymptotic value at high flow rates. If the plots of BHP versus Qp for various THPs cross, this means that there are two possible THPs for a given BHP. This may be legitimate if the BHP has been set artificially high to indicate supersonic flow or breach of erosion velocity limits. Otherwise, the cause should be established and the tables altered to remove the crossing curves as they are highly likely to cause convergence problems in ECLIPSE. • Export the tables from VFPI and INCLUDE them in the ECLIPSE dataset • If the tables contain legitimate crossing curves insert the VFPCHK keyword to set a threshold pressure above which intersections between VFP curves will not be treated as erroneous. • VFP tables are interpolated linearly by default. In some instances this can artificially place emphasis on those points closest to the tabulated VFP curves in the ALQ dimension. To enable cubic spline interpolation of the VFP tables insert the VFPTABL keyword. This is intended for use in situations where the choice of ALQ is critical, such as in the ECLIPSE 200 GAS LIFT OPTIMISATION facility. • Set maximum THP limits for each well as necessary using WTHPMAX. • Insert the EXTRAPMS keyword to provide messages in the event of VFP table extrapolation. In the event of well convergence problems, this may assist in identifying whether extrapolations of VFP tables into regimes of unrealistically low or high flow rate or pressure are leading to convergence problems.
- 373. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 373 of 499 08/04/99 • Assign VFP tables to wells and / or flow lines using WCONPROD, WCONINJ, WCONINJE or GRUPNET as appropriate. • If matching well performance, the WVFPDP keyword can be used to modify the flowing BHP at a given THP. This is done by either adding a fixed pressure (which may be negative) to the BHP calculated from the VFP tables, or by scaling the BHP linearly according to a user-defined scale factor.
- 374. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 374 of 499 08/04/99 Drilling a Well: WELSPECS Figure 124: General well specification • WELSPECS is equivalent to drilling a well • Properties of the well as a whole are set with WELSPECS • WELSPECS must precede other keywords referring to the drilled well. • Wells will be opened in the order they are specified in WELSPECS; this is the automatic drilling queue. Drilling queues can also be created manually using QDRILL. • The maximum number of wells drilled must be specified in the RUNSPEC section using the WELLDIMS keyword WELSPECS --1 2 3 4 5 6 --Well Group Wellhead Wellhead BHP Flowing --Name Name I location J location Datum Phase Name Group I J Middle location location/ --7 8 9 10 11 --Drainage Inflow Xflo when Xflo when Fluid --Radius Equation Shut in Flowing PVT -- table --12 13 --Fluid FIP --Density calc Region
- 375. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 375 of 499 08/04/99 Drilling a Well: WELSPECS The WELSPECS keyword is required prior to any other data for the well. It is used in history matching and prediction runs. Wells drilled by WELSPECS during the history matching phase do not need to be re-specified if the simulation progresses to prediction mode. Some of the notes on the keyword do not apply to history matching runs; this is clarified where appropriate. WELSPECS specifies the I, J location of the wellhead, its name and the group to which it belongs. WELSPECS must be specified for each well and may be placed at the beginning of the SCHEDULE section or else at the time at which a well comes on stream. WELSPECS may contain any number of records separated by a forward slash; an additional forward slash terminates the WELSPECS keyword. The record contents are: Well name. Mandatory. This must be no longer than 8 characters and need not be enclosed in inverted commas. Name of the group to which the well belongs. Mandatory. This must be no longer than 8 characters and need not be enclosed in inverted commas. The group named FIELD is always present and cannot be used here. In history matching the user is often concerned with individual well rates. Thus, there is usually a need for only one group containing all the wells. If, however, wells have been amalgamated into so-called “super-wells”, a hierarchy needs to be created and the phase flow rates of the groups containing wells only are matched to observed flows. In this case and in prediction runs where there may be a complex hierarchy note that no group may contain wells as well as groups. A well can be re-assigned to a different group during the simulation by specifying WELSPECS with a different group name. I – location of the well head. Mandatory. J- location of the well head. Mandatory. For vertical wells the I and J locations of the well head are only used for reporting purposes. For friction wells the I and J locations of the well head are taken as the location of the heel of the well and define the order in which the well connections are arranged. This influences the calculation of frictional pressure drops along the wellbore. BHP datum depth. This is the reference depth from which the well BHP is measured and should be either:-
- 376. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 376 of 499 08/04/99 • Situated close to or at one of the perforations. • Set to the reference depth of the well VFP curve. If defaulted or set to a negative value this is set equal to the centre depth of the uppermost connecting grid block. Preferred phase of the well. Mandatory. OIL or O WATER or W GAS or G LIQ or L This need not be enclosed in inverted commas. The item can be abbreviated; only the first letter is significant. The preferred phase influences the well productivity or injectivity index calculation via the mobility. The phase flow for a well having a single connection is given by: PPIQp ∆= . EQ. 60 PMTQ pwjp ∆= EQ. 61 )( ghPlPMTQ bhpcelpwjp ρ+−= EQ. 62 where Mp is the phase mobility, Tw transmissibility from well to connecting cell and ∆P the drawdown. The drawdown contains contributions from the cell pressure, Pbhp is the BHP in the wellbore at the connection and the remaining term is the hydrostatic head correction between the connection depth and the BHP reference depth. The subscript p refers to produced or injected phase. Production Well Mobility For producers the mobility of the produced phase into the completion is given by p rp p K M µ = EQ. 63
- 377. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 377 of 499 08/04/99 Injection Well Mobility For injectors, however, the phase mobility can be calculated in one of two ways. The default is ++= g rg w rw o ro p p KKK B M µµµ 1 EQ. 64 where Mp is the mobility of the phases displaced by injection. If this were calculated in the same manner as the produced phase mobility then, for instance, injection of water into a cell having a water saturation below the critical water saturation could not take place since water mobility would be zero. In reality, the saturation of the injected phase in the near-wellbore region would be high. Then, most of the pressure drop occurs close to the wellbore and the injectivity varies until the grid block is flooded out. If the grid block is much larger than this region, the calculated injectivity is incorrect until the entire block is flooded out. The COMPINJK keyword allows users to deal with this problem by influencing phase mobility via the well relative permeability. This improves accuracy in cases where: • The well injects fluid with mobility significantly different from that of the grid block • The grid blocks are large and • The well is not subject to crossflow The relative permeability of the injected phase is given a constant value kr(p,*) while the relative permeabilities of the other phases are set to zero. The injector well mobility in any given connecting grid block is then pp r p B pk M µ ,*)( = EQ. 65 NOTE that an injection well with a fixed kr(p,*) value must not be allowed to crossflow because this will result in multiphase injection. In this event, ECLIPSE resets the crossflow flag in item 10 of WELSPECS to prevent this.
- 378. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 378 of 499 08/04/99 Drainage radius. This is used in the productivity or injectivity calculation and is also known as the Peacemann radius. The instantaneous well productivity or injectivity (PI) is printed in the well reports if requested using RPTSCHED. NOTE. The PI reported in the .PRT and/or .LOG file is valid if the drainage radius is known. Otherwise, the PI is grid cell size dependent If this item is set to zero the pressure equivalent radius of the connecting grid block will be used. For multiple connections the well PI is given by ∑= j pjwjMTPI EQ. 66 Where the subscript j refers to the well connections. The calculation of connection transmissibility Twj is discussed in Connection Specification: COMPDAT, p.384. If a negative drainage radius is specified here the well reports contain the potential well flow rate, which is the flow in the absence of all constraints except for BHP and THP. Well inflow equation. This invokes a special inflow equation to model free gas flow between the well and connecting cells:- • R-G The Russell Goodrich Equation • P-P The gas pseudo-pressure equation • STD or NO The standard inflow equation, which is the default. This need not be enclosed in inverted commas; only the first character is significant. The significance of this term is in alternative calculation of the flow between well and connecting cell to compensate for flow regimes, which may be encountered in the near- wellbore region of high-rate gas wells. The finite difference forms of the diffusivity equations on which reservoir simulation is based are approximate: among the assumptions made is low compressibility. This may not be valid in the vicinity of a high-rate gas well at high pressure. Instruction for automatic shut-in • STOP Allow crossflow when the well is shut in at the surface. • SHUT Prohibit crossflow, isolating the well from the formation. This is the default.
- 379. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 379 of 499 08/04/99 Crossflow while flowing flag • YES Allow crossflow during flow, which is the default • NO Prohibit crossflow during flow. PVT table This points to the PVT table used to calculate wellbore fluid properties. ECLIPSE considers the fluid within the wellbore to be a uniform mixture. The calculation of the hydrostatic head at formation level and the conversion of reservoir flow rate to surface rate depend on the choice of formation volume factor. If a zero value is entered here (which is the default) ECLIPSE will use the PVT table assigned to the lowest cell in which the well is completed. Type of density calculation for wellbore hydrostatic head. • SEG Segmented density calculation. The flowing mixture density is calculated between each adjacent pair of connections. Compared to the alternative, this is more accurate if different mixtures of fluids enter the wellbore at various connections but is an explicit calculation. This is the default. • AVG Average density calculation. The flowing mixture density is uniform at formation level and is calculated implicitly. Fluid-in-place (FIP) region number. A number of well control modes in which the well is subject to control from a higher level in the group hierarchy require calculation of net voidage, which in turn requires that the well be assigned to a specific FIP region to which it contributes voidage. If a zero value (which is the default) is entered here the average hydrocarbon conditions in the field will be used. If a negative value is entered here the FIP region number of the lowest connected grid cell will be used. If a positive number is entered, this will be taken as the required FIP region number. During a history match models may be run under a regime of voidage replacement i.e. replacement of all produced fluid volumes at reservoir conditions. The calculation of voidage is based on the fluid-in-place calculation. So, in order to calculate the voidage at group or field level, each well has to be assigned to a particular fluid-in-place region. This is also needed for injectors to specify the right amount of voidage replacement at group or field level. Refer also to the section on Group Controls
- 380. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 380 of 499 08/04/99 Gas Flow in Wells Figure 125: Flow in gas wells • A number of distinct flow regimes exist in gas wells depending on the BHP • The ECLIPSE default is most appropriate for pressures above 3500 psia • For other regimes the inflow performance for free gas needs to be modified • The back pressure equation is used at low pressure • The Russell Goodrich Equation is a refinement of the back pressure equation • At intermediate pressures the pressure is replaced by the pseudopressure m(P) 2000 3500 PQ α)(PmP →2 PQ α P/µz P (psia)
- 381. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 381 of 499 08/04/99 Gas Flow in Wells Low Pressure gas wells Free gas compressibility is given by z P zP Cg ∂ ∂ += 11 EQ. 67 Where z is the real gas z factor. At pressures up to approximately 2000 psia, the free gas compressibility is dependent largely on pressure alone P Cg 1 ≈ EQ. 68 where Cg is measured in (psia)-1 . At a pressure of 1000 psia gas compressibility is therefore approximately 10-3 (psia)-1 , which is three orders of magnitude higher than a typical oil or water compressibility. Most simulators treat reservoir fluid compressibilities as being relatively small and do not account for such high compressibilities. ECLIPSE can include this effect only for flow between completion and connecting cell by using a modified form of Darcy’s Law for compressible fluids: )P-PC(=q 2 BHP 2 resg EQ. 69 where qg is the surface gas flow rate , Pres the average static pressure in the drainage area and Pbhp the flowing bottom hole pressure. The coefficient C contains all other contributions including gas viscosity, permeability to gas flow, temperature, net thickness etc. As it stands EQ. 69 does not account for near-wellbore turbulent flow. The following modified version does and is known as the back pressure equation. )P-PC(=q n2 BHP 2 resg EQ. 70 NOTE. This only applies to the flow between each connection and the connecting cells. Highly compressible flow in the reservoir grid is not accounted for. Non-Darcy flow in the reservoir is also not accounted for. The Russel Goodrich Equation The Russel Goodrich equation is
- 382. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 382 of 499 08/04/99 +− S r r )P-P( z2 1 T25152P khT =q w e 2 BHP 2 res sc sc s 4 3 ln µ EQ. 71 Note this equation has the form of the backpressure equation with n = 1 and S+ 4 3 - r r 1 z2 1 TP252152 khT=C w esc sc ln µ EQ. 72 ECLIPSE uses a simplified form of this equation, which has greatest error at large values of drawdown The Gas Pseudopressure The inflow performance for a gas well can also be written using the pseudo pressure. This pseudo pressure is defined as: dp z P 2=m(p) P P∫ 0 µ EQ. 73 Where P = pressure, psia P0 = some arbitrary low base pressure, psia µ = viscosity at pressure P, cP z = dimensionless z factor at pressure P. In other approaches the approximation 2 PQα EQ. 74 Holds reasonably well provided the product µz remains constant. This assumption is most difficult to defend in the pressure range between approximately 2000 to 3500 psia. The replacement of P by m(P) deals implicitly with the variations in z factor and viscosity. Although using m(P) in place of P will always give better results, the extra accuracy is not usually needed below 2000 psia or above 3500 psia.
- 383. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 383 of 499 08/04/99 Standard Inflow Equation For pressures higher than approximately 3500 psia the gas pseudopressure is very nearly linear in P. The approximation PQα i.e. the standard inflow equation, is accurate enough for most purposes.
- 384. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 384 of 499 08/04/99 Connection Specification: COMPDAT Figure 126: Specifying connections using COMPDAT • COMPDAT is required for all wells and cannot precede WELSPECS • Locations and properties of connections are specified using COMPDAT • A connection is the combination of all completions located in a single grid block • The well will only produce or inject if it has open connections • This can be used as a workover keyword to modify connection properties, and open and shut them • The maximum number of connections per well must be specified in the RUNSPEC section using the WELLDIMS keyword COMPDAT --1 2 3 4 5 --Well I J K K --Name Upper Lower ’P*’ 1* 1* 1 10 --6 7 8 9 10 --Open/ Saturation Connection Wellbore Effective --Shut Table Factor Internal Kh -- Diameter OPEN 1* 1* 0.583 / --11 12 13 14 --Skin D Penetration Pressure Equivalent --Factor Factor Direction Radius --Record of data for well I20 I20 1* 1* 1 5 OPEN 1* 1* 0.583 / /
- 385. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 385 of 499 08/04/99 Connection Specification: COMPDAT The COMPDAT keyword is used to specify which cells the well is connected to. A connection is the sum of all of the completions or perforations that happen to be located in the grid cell. COMPDAT is also used to specify the properties of each connection so that the completions that make up the connections can be meaningfully combined and the engineer can use completion data from other sources. The keyword is followed by any number of records, each terminated by a forward slash; an additional forward slash terminates the COMPDAT keyword. The record contents are: Well name or well name root. Mandatory. A well name root , ending with an asterisk (*) can be used to refer to several wells in one record I – location of the connecting grid block(s). If a default, zero or negative value is entered ECLIPSE will use the I – location of the well head entered in WELSPECS. J– location of the connecting grid block(s). If a default, zero or negative value is entered ECLIPSE will use the J – location of the well head entered in WELSPECS K – location of the upper connecting grid block. Mandatory. K – location of the lower connecting grid block. Mandatory. This is a convenient format for specification of vertical wells since only the I and J locations and a range of K indices need to be specified. To specify a horizontal well one record per connection has to be used, where the upper and lower K indices are the same and I and J vary from connection to connection. Note that ECLIPSE lacks the geometrical information to place a connection anywhere other than the centre of the cell and treats the well as if perforated throughout the cell from one cell face to the opposite face. If well trajectory data is imported from other applications such as SCHEDULE or GRID, the same applies. In effect, ECLIPSE shifts connections to the centres of the nominated cells. This cannot be compensated for directly and causes a number of potential problems such as those listed below. These are discussed in more detail later in this section. Alteration of the hydrostatic head term in the well inflow performance relationship on account of change of depth of the connection. The most direct way to correct this is to
- 386. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 386 of 499 08/04/99 build a Local Grid Refinement (LGR) around the well such that the connection depths remain unchanged when the well is completed in the LGR. Altered water breakthrough times. Since the connection is moved within the cell, the time taken for a waterfront to reach the connection will change. This has to be dealt with by specifying a different well connection saturation table as described below. This should not be modelled by changing the critical water saturation of the cell as that alters the flow to neighbouring grid cells. Modified well connection factor. This is equivalent to introducing partial penetration where none exists and is discussed below. The following data then applies to each connection with K – locations between the upper and lower values specified Open/shut flag. • OPENThe connection is open to flow (the default) • SHUTThe connection is closed • AUTOThe connection is closed initially but will be opened when another connection in the well is closed by an automatic workover. AUTO connections are opened every time the well is worked over in the order they are set in COMPDAT. Such connections are also opened when production rate targets must be met if the REPERF action is selected while using the Group Production Rules defined in the PRORDER keyword. Saturation table for connection relative permeabilities. If default, zero or negative this is set to the saturation table of the connecting cell. It may be necessary to refer to non-default relative permeability tables here to deal with effects such as delayed water breakthrough on account of non-central location of the connection in the cell. If the Vertical Equilibrium option is active (keyword VE in the RUNSPEC section) the end-points of the saturation table are used to calculate the contact depths and relative permeabilities at the well connection. If hysteresis is active (keyword SATOPTS in the RUNSPEC section) the table referred to here applies to drainage and imbibition. Use the COMPIMB keyword to nominate a different saturation table for imbibition at the well connection.
- 387. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 387 of 499 08/04/99 Connection transmissibility factor. This is also known as the well connection factor. If a zero, default or negative value is set here ECLIPSE will calculate a connection factor based on the remaining items in this record from the following. g w e wj qDS r r cKh T ++ = ln θ EQ. 75 Which is derived on the assumption of steady-state cylindrical flow from a homogenous medium into a vertical wellbore. The Peacemann radius re, also known as pressure equivalent radius is given by ( ) ( ) xy xy e KK DYKDXK r + + = 22 28.0 EQ. 76 This is the radius at which the pressure in a steady-state homogeneous vertical cylindrical system is the same as the cell pressure. If the x and y permeabilities and cell dimensions are identical, xre ∆≅ 2.0 EQ. 77 The Peacemann radius will fall within a cell if the aspect ratio of the cell is low. If the cell is long and narrow, for instance, a connection factor will be calculated that reflects flow from a location beyond the connecting cell. Output of Twj and Kh can be requested using RPTSCHED. If a no-flow barrier is modelled as a cell with zero permeability this will produce a nonsensical well connection factor. Alternative means for modelling shales and other no-flow barriers should be used. If a well is located at the edge of a Cartesian grid block or next to a column of inactive cell then its PI should be halved using WPIMULT. If it is located at the corner of a Cartesian grid or does not flow in all directions for another reason, its PI should be quartered or reduced as appropriate using WPIMULT. A well connection in the outer-most block of a radial grid will be treated as a connection around the entire boundary of the block and the calculated connection factor will be much too large. If the well cannot be moved, then either add an extra ring of inactive cells around the model or supply an appropriate connection factor.
- 388. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 388 of 499 08/04/99 The actions taken by ECLIPSE in calculating the various quantities in the well connection factor depend on which are supplied and whether the values are positive • If Kh is default or negative and rw and Twj are set then Kh will be calculated from T and the remaining terms. Kh will only be used for reporting purposes • If Kh>0 and Twj is set the denominator term will be calculated from T and Kh • If Kh=0 and Twj is set, Kh will be replaced by the effective block Kh and the denominator will be calculated as if Kh had been set to >0 • Recalculation of Kh or the denominator term can be stopped by setting the 45th switch of the OPTIONS keyword to >0 provided that the connection factor is positive. This causes the denominator term to be calculated from the cell dimensions and wellbore radius. This achieves back-compatibility with pre-95a datasets if required. The denominator term will be used to calculate the well PI. If a positive values is entered for Twj this should include the effect of skin factor but exclude the effect of the D factor. The D factor is accounted for by mobility adjustment as described in the ECLIPSE 100 TECHNICAL DESCRIPTION. The default connection factor calculated by ECLIPSE is unlikely to be realistic Partial penetration will affect the Kh value. Ideally the effective Kh should be derived from well tests. Although connections are vertical by default, for horizontal or deviated completions, the cell dimensions used in EQ. 76 are altered as appropriate. Such completions will have a drainage radius containing a contribution from the block height. As this cannot be accounted for it may be appropriate to supply a connection factor Wellbore internal diameter at the connection. Mandatory. This is required to calculate Twj, the well PI and the effects of the D factor. Effective Kh of the connection. The default value is negative, in which case see above. Skin factor. This defaults to zero. Large negative skin factors may increase the effective wellbore radius to the pressure equivalent radius of the grid block. This causes high values of Twj, which may cause convergence problems. Warnings will be issued if the effective wellbore radius increases beyond half of re. If the effective wellbore radius is larger than re,. Twj becomes negative and an error results. Since the skin factor is an indirect
- 389. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 389 of 499 08/04/99 means of modelling other phenomena and a negative skin factor has no physical basis it may be appropriate to replace the negative skin factor by an increased permeability near the wellbore. D factor. This is used to model the flow-dependent skin factor arising in non-Darcy flow of free gas near the well. The skin factor S normally contains components representing formation damage or stimulation, well bore deviation, partial penetration and other contributions. The rate-dependent skin transforms the skin factor gqDSS +→ EQ. 78 Where qg is the free gas flow through the connection. The D factor is usually obtained for the well as a whole and multiplied by the total free gas flow rate. More precisely, the effect of non-Darcy flow depends on the flow rate at individual connections, so ECLIPSE calculates the non-Darcy skin from the connection flows rather than the well flow. If the well has more than one connection the D factor is scaled amongst them such that each connection has the same initial non-Darcy skin i.e. the connection D factors are inversely proportional to the connection free gas flow rates. Drawdown and free gas mobility are assumed the same in each connection for D factor scaling purposes. The connection D factor, if known, should be set in COMPDAT as a negative number. ECLIPSE applies this to the connection without scaling. The D factor can be set using the WDFAC keyword, in which case it is specified as a positive number. In this case the scaling described above is applied. Penetration direction • X • Y • Z – the default This applies to Cartesian grids. In radial grids only the Z direction is permitted. NOTE. ECLIPSE orders vertical connections by depth. For a horizontal or multilateral well the ordering is heel-to-toe starting from the well head location specified in WELSPECS. If more than one connection is a candidate for the heel, ECLIPSE selects the shallowest. If a unique sensible ordering cannot be found a warning is issued. When the
- 390. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 390 of 499 08/04/99 Wellbore Friction option is active the connection ordering should be specified using WFRICTN or WFRICTNL Pressure Equivalent Radius This is used in the calculation of individual connection transmissibility factors. If a positive value is entered here the pressure equivalent radius is set to this value instead of being calculated from grid block dimensions and properties according to Peacemann’s formula (EQ. 76, on page 387). The pressure equivalent radius is not used for connections in the innermost or outermost cells of a radial grid or LGR. The default is to calculate the pressure equivalent radius from Peacemann’s formula.
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- 392. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 392 of 499 08/04/99 Partial Completion: COMPRP Figure 127: Rescaling saturation tables at well connections: COMPRP • By default the perforation extends through the entire grid block • Partial completions are completions in which not all of the grid block is perforated and/or the well is not located at the grid block centre. • COMPRP is used to specify partial completions when Vertical Equilibrium is not in use • The top and bottom of the perforated interval are converted to gas and / or water saturations at which the well produces gas and / or water • COMPRP must not precede COMPDAT. • COMPRP has been largely superseded by COMPVE (see Partial Completion with VE: COMPVE)
- 393. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 393 of 499 08/04/99 Partial Completion: COMPRP COMPRP uses endpoint scaling to account for the location of perforations and the distribution of fluids in cells that are large compared to the perforation intervals. If a completion extends from the top to the bottom of the connecting grid cell we may expect water to be produced when the water saturation reaches the critical value, Swcr, in the absence of formation damage. If the completions do not extend to the bottom of the cell, no water production is expected until the contact reaches the lowest open completion. The water saturation in the cell is, however, evenly distributed, hence the critical water saturation must be modified to emulate the behaviour of an advancing water contact. Endpoint scaling of the well connection saturation table is the means chosen to do this. This is the purpose of the COMPRP keyword. Note that this applies in the case of dispersed flow. When the Vertical Equilibrium (VE) option is active, ECLIPSE tracks the fluid contacts in each grid cell and a different approach is taken to model partial penetration. Refer to the section on “Partial Completion with VE: COMPVE” for more information. COMPRP is followed by any number of records, each terminated by a forward slash. The set of records must be terminated by a forward slash. The record items are: Well name or well name root. Mandatory. A well name root ending in an asterisk (*) can be used to refer to several wells. I – location of connecting grid blocks. This defaults to zero, i.e. any I - value J – location of connecting grid blocks. This defaults to zero (i.e. any J – value) K – location of upper connecting grid block. This defaults to zero, which is taken as the uppermost connection of the well. K – location of the lower connecting grid block. This defaults to zero, the lowest connection of the well. Saturation table for relative permeability. A zero or positive value over-rides the saturation function specified in COMPDAT. A zero value will use the saturation table for the connecting cell. A negative value will not affect the saturation table number. This is the default.
- 394. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 394 of 499 08/04/99 If hysteresis is in use the table referred to here will apply to drainage and imbibition. Connection saturation table re-scaling is not allowed if the imbibition and drainage table numbers are different. The remaining items are the scaled values of the connate and critical water and gas saturations, Scaled value of the connate water saturation, SWMIN. This defaults to Swco and is ignored in problems not containing water. Scaled value of the maximum water saturation, SWMAX This defaults to 1-Sowcr in oil-water problems and 1-Sgcr in gas-water problems. It is ignored in problems not containing water. Scaled value of the critical gas saturation, SGMIN. This defaults to Sgcr and is ignored in problems not containing both gas an oil Scaled value of the maximum gas saturation, SGMAX. This defaults to 1-Sogcr-Swco and is ignored in problems not containing both gas an oil Refer to the keyword description in the ECLIPSE 100 REFERENCE MANUAL for a more comprehensive explanation of the interaction of this keyword with the endpoint scaling option for grid cells and representation of the effects of partial penetration.
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- 396. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 396 of 499 08/04/99 Partial Completion with VE: COMPVE Figure 128: Partial completions in VE and diffuse flow models: COMPVE • By default the perforation extends through the entire grid block • Partial completions are completions in which not all of the grid block is perforated • When Vertical Equilibrium (VE) is active ECLIPSE tracks the locations of fluid contacts in each grid cell. • The Vertical Equilibrium option is discussed in detail in the ADVANCED ECLIPSE 100/200 USER COURSE offered by GEOQUEST. • COMPVE sets the depths of well connections and cells when VE is in use. • COMPVE is also usable without the VE option. • COMPVE must not precede COMPDAT. Sw=1.0 Sw=1-Sor Sw=Swc OWC Htot Ho Hw DX DY Only clean oil is produced
- 397. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 397 of 499 08/04/99 Partial Completion with VE: COMPVE COMPVE is used to model the effect of partial penetration when VE is active. In VE the phase flows at a well connection depend on the contact depths and the relative permeabilities at the connection. The relative permeabilities depend on the connection top and bottom depths and the critical and maximum values of the flowing phase saturations. ECLIPSE tracks the contact depths in a VE run but the connection relative permeabilities and perforation intervals must be supplied. If COMPVE is not used, the top and bottom depths of each connection are set to the depths of the centres of the upper and lower cell faces, respectively. COMPVE can optionally recalculate the connection skin factor to account for partial penetration. COMPVE is followed by any number of records, each terminated with a forward slash. A forward slash terminates the keyword. Well name or well name root. Mandatory. A well name root ending in an asterisk (*) can be used to refer to several wells. I – location of connecting grid blocks. This defaults to zero, i.e. any I - value J – location of connecting grid blocks. This defaults to zero (i.e. any J – value) K – location of upper connecting grid block. This defaults to zero, which is taken as the uppermost connection of the well. K – location of the lower connecting grid block. This defaults to zero, which is taken as the lowest connection of the well. The following data applies all the connections in the well that match the location indices in items 2-5. Of a location index is defaulted to zero it plays no part in selecting the connections to which the following data applies. So, if the I and J locations are defaulted the data applies to all connections located between K1 and K2. If all four locations are defaulted the following data is applied to all of the well connections. Saturation table number for connection relative permeabilities. The endpoints of this table will be used to set the relative permeabilities in each saturation zone to calculate the mobilities at the well connection. If this item is zero or
- 398. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 398 of 499 08/04/99 positive it will over-ride the saturation table set in COMPDAT. If zero, the saturation table of the connecting cell will be used. If negative (which is the default) the saturation table specified in COMPDAT will be used. CVEFRAC This is the fraction of Vertical Equilibrium curves to be used in calculating relative permeabilities for the connection DTOP. Top depth of the top connection in the set matching the location indices in items 2-5. DBOT. Bottom depth of the bottom connection in the set matching the location indices in items 2-5. Flag to re-calculate the skin factor taking account of partial penetration. • NO is the default; the skin factor set in COMPDAT will be used • YES The skin factor will be calculated from Odeh’s correlation and will be used in place of that supplied in COMPDAT; the connection transmissibility will then be re- calculated. The well bore diameter must be set in COMPDAT. The skin factor and transmissibility will be recalculated every time a plug-back takes place. In cases of partial penetration the convergence of the fluid flow lines towards the perforated interval is different from the case of total penetration. This can be treated as an additional component of the skin factor. For a well subject to partial penetration the total mechanical skin factor is pd p t SS h h S += EQ. 79 where ht is the formation thickness hp is the perforation interval Sd is the damage skin factor Sp is the partial penetration skin factor Sp is calculated from a correlation .[6]
- 399. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 399 of 499 08/04/99 ( ) ( )[ ] ( ){ }wctprtpr rhh hp ht Sp lnln1.049.095.17ln135.1 825.0 +−−+ −= EQ. 80 Where h v t tpr K K h h = EQ. 81 += 753.22126.0exp t m wwc h z rr EQ. 82 zm is the distance between the middle of the perforated interval and the top or bottom of the formation, whichever is nearer rw is the wellbore radius All lengths are specified in feet. The connection factor is the derived using the new value of the skin factor. As partial penetration effects are contained in the new skin factor, the effective Kh should be based on the formation thickness ht, not the perforation interval hp. If the formation is divided vertically into two or more layers of grid blocks the skin factor is calculated separately for each completed layer. Then GTOPGBOTht −= EQ. 83 DTOPDBOThp −= EQ. 84 ( ) ( ){ }DBOTDTOPGBOTGTOPDBOTDTOPMINzm +−−+= 5.0,5.0 EQ. 85 Sd the damage skin factor. This defaults to zero. GTOP. Depth of the top of the grid cell at the position of the well connection. This is only relevant if the skin factor is to be recalculated for partial penetration and the well is
- 400. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 400 of 499 08/04/99 located off-centre in a sloping cell. The default is the depth of the centre of the top face of the connecting cell. GBOT. Depth of the bottom of the grid cell at the position of the well connection. This is only relevant if the skin factor is to be recalculated for partial penetration and the well is located off-centre in a sloping cell. The default is the depth of the centre of the bottom face of the connecting cell.
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- 402. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 402 of 499 08/04/99 Measured Well Production Rates: WCONHIST Figure 129: Historical rate specification using WCONHIST • WCONHIST is used to specify measured well rates for each flowing phase • The rates are not used as upper limits • Simulated and measured rates are reported for comparison • The rates are specified for many reporting periods, often at monthly intervals • WCONHIST cannot precede COMPDAT • WELTARG can be used to modify measured rates after WCONHIST; see the section on “Modifying Well Targets: WELTARG”, p.427 WCONHIST --1 2 3 4 5 --Well Open/ Control Observed Observed --Name Shut Mode Oil Rate Water Rate P1 OPEN ORAT 3000 / P21 OPEN ORAT 2000 / / --6 7 8 9 10 --Observed VFP ALQ Observed Observed --Gas Rate Table THP BHP
- 403. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 403 of 499 08/04/99 Measured Well Production Rates: WCONHIST At its simplest the WCONHIST keyword is used during history matching to set the measured phase flow rates for wells whose production is known. These measured flow rates set with WCONHIST are not used as upper limits during the simulation. For instance, if a well’s simulated water rate exceeds the value set in WCONHIST the well will not automatically be moved to control by water rate. This is because during history matching the engineer is investigating the mechanisms responsible for watering out of the well, not the surface facilities. During the early stages of history matching, the production rates calculated by ECLIPSE are unlikely to match the measured rates set in WCONHIST; both sets of rates may be output by ECLIPSE for comparison. An important application of WCONHIST is to set the correct voidage during the early stages of history matching. If the wells are under RESV control, the net voidage is known. With reference to the definition of compressibility P V V Ct ∂ ∂ = 1 EQ. 86 Where Ct is the total system compressibility. If Ct is approximately correct, WCONHIST defines the correct volume change if all wells are under RESV control. Then, the initial volume, V, is altered by the engineer to influence the simulated pressure drop and match it to the measured pressure drop. If the model contains an entire field, V is its volume. If the model is a single well, V refers to the volume within the well drainage radius. If the well is under LRAT control, it will produce at a rate equal to the sum of the surface flow rates of oil and water . If the well is under another control mode the phases will be produced according to their mobility ratios . WCONHIST can be followed by any number of records, each terminated with a forward slash. The keyword is terminated by a forward slash. The record items are: Well name or well name root. Mandatory. This must be no longer than 8 characters and is not case sensitive. Well status:- • OPEN or O The well is open for production. This is the default • SHUT or SH The well is isolated from the formation; crossflow is prohibited
- 404. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 404 of 499 08/04/99 • STOP or ST The well is stopped; crossflow is allowed. The combination of this flag and the shut-in and cross-flow ability flags in the section on “Drilling a Well: WELSPECS” determine the circumstances in which crossflow is allowed in the well.: The flags in WELSPECS determine whether crossflow is permitted before production (or injection) and after shut-in. The status flag in WCONHIST determines whether cross-flow is allowed during production. Control Mode. Mandatory. • ORAT Controlled by the observed oil rate • WRAT Controlled by the observed water rate • GRAT Controlled by the observed gas rate • LRAT Controlled by the observed liquid (oil + water) rate • RESV Controlled by the observed reservoir volume rate This keyword can be overwritten by the WHISTCTL keyword, which is a shorter alternative means of specifying history matching well control mode. Note that the control modes BHP and THP are absent. A history matching well’s THP is reported as zero unless VFP tables are in use. The BHP limit is set to 1 atmosphere (14.7 psi or 0 psia) when WCONHIST is first declared. A well might move to BHP control if its PI is poorly matched. This would suggest a poorly matched Kh or skin factor. If necessary, the BHP limit can be reset using WELTARG after WCONHIST. Observed oil production rate. This defaults to zero. Observed water production rate. This defaults to zero. Observed gas production rate. This defaults to zero. NOTE. At least one of these three items must be non-default. VFP table number. This defaults to whichever value was previously set.
- 405. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 405 of 499 08/04/99 If no VFP tables are in use the THP is not calculated and is reported as zero. If this is set to >0 the THP is calculated and reported but the well is not permitted to go to THP control. Artificial Lift Quantity (ALQ) to be used in THP calculation. This defaults to whichever value was previously set. If defaulted, the THP is not calculated. Observed THP. This defaults to zero; it is not a limit. Any value set here is used only for reporting purposes; the well will not be transferred to THP control if the tubing head pressure falls below the value set here. Observed BHP. This defaults to zero; it is not a limit. Any value set here is used only for reporting purposes; the well will not be transferred to BHP control if the tubing head pressure falls below the value set here. NOTE. The well may transfer to BHP control if the BHP limit is modified using WELTARG (after WCONHIST). This is to help ensure that a well does not move to BHP control before its PI has been properly matched. Change to BHP control at atmospheric pressure suggests that the well Kh or skin is poorly matched. NOTE: WHISTCTL can be used to modify history matching well control modes. WCONPROD can also be used during history matching; see the section on Setting Well Target Rates: WCONPROD, p.436
- 406. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 406 of 499 08/04/99 Well Injection Rates: WCONINJE Figure 130: Setting injection rate using WCONINJE • WCONINJE is used to set individual well injection rates during history matching and prediction • WCONINJE is also used to set injection pressure constraints during history matching • WCONINJ is an alternative, which does not permit group control. It is virtually obsolete. • A brief description of the items in the WCONINJE records follows. For a full description, see the keyword description in the ECLIPSE 100 REFERENCE MANUAL WCONINJE --1 2 3 4 5 --Well Injected Open or Control Surface --Name Phase Shut Mode Flow Rate I20 WAT OPEN RATE 8000 / / --6 7 8 9 10 --Reservoir BHP THP VFP Rs or --Flow Rate Target Target Table Rv
- 407. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 407 of 499 08/04/99 Well Injection Rates: WCONINJE WCONINJE is used to control rates and set limiting pressures for individual injection wells. The major differences between this and production control keywords such as WCONHIST arise because injectors are single phase and the changes between well control modes are generally more straightforward. WCONINJE has a facility for setting the vaporised oil concentration in injected gas (Rv) or dissolved gas concentration in injected oil (Rs). The keyword may be followed by any number of records. The contents of each record are: - Well name or root. Mandatory This must be no longer than 8 characters and is not case sensitive. Injector type i.e. injected phase. Mandatory. • OIL or O • WATER or W • GAS or G Open/shut flag • OPEN The well is open for injection. This is the default • SHUT The well is isolated from the formation; crossflow is prohibited • STOP The well is stopped; crossflow is allowed. • AUTO The well is initially SHUT but will be opened automatically as soon as constrints on drilling rate (WDRILTIM) rig availability (GRUPRIG) and maximum number of open wells (GECON) allow. The combination of this flag and the shut-in and cross-flow ability flags in the section on “Drilling a Well: WELSPECS” determine the circumstances in which crossflow is allowed in the well. Control mode. Mandatory. • RATE Controlled by surface volume rate target • RESV Controlled by reservoir volume rate target • BHP Controlled by BHP target • THP Controlled by THP target
- 408. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 408 of 499 08/04/99 • GRUP The well injects its share of a group or field target as set with GCONINJE. Surface flow rate target This defaults to infinity Reservoir volume flow rate target This defaults to infinity BHP target This defaults to 1.0E5 psia or 6895 barsa or 6804 atma. THP target NOTE. At least one of these four items must be non-default. VFP table This defaults to zero and should be left defaulted if not THP calculations are required. Rs or Rv of injected oil or gas as appropriate This defaults to zero.
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- 410. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 410 of 499 08/04/99 Simulator Control: TUNING, TUNINGL and NEXTSTEP Figure 131: Setting convergence criteria using TUNING and TUNINGL • TUNING is used to specify convergence, iteration and timestepping criteria for the global portion of the model • TUNINGL is used to specify the convergence, iteration and timestepping criteria for all of the LGRs in the model • NEXTSTEP sets the duration of the next timestep • Timestepping controls need alteration fairly frequently • Iteration controls seldom need adjustment • Convergence controls need adjustment only in highly unusual circumstance TUNING --Mnemonics represent Timestepping and convergence criteria --Record 1 contains timestepping controls --These are quite frequently set to non-default values --TSINIT TSMAXZ TSMINZ TSMCHP TSFMAX --TSFMIN TSFCNV TFDIFF THRUPT / --Record 2 contains time truncation and convergence controls --These should be altered only in extreme cases --TRGTTE TRGCNV TRGMBE TRGLCV XXXTTE --XXXCNV XXXMBE XXXLCV XXXWFL TRGFIP --TRGSFT / --Record 3 contains iteration controls --These seldom need adjustment --NEWTMX NEWTMN LITMAX LITMIN MXWSIT --MXWPIT DDPLIM DDSLIM TRGDPR XXXDPR/
- 411. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 411 of 499 08/04/99 Simulator Control: TUNING, TUNINGL and NEXTSTEP TUNING and TUNINGL The TUNING and TUNINGL keywords are used to specify the timestepping and convergence criteria for the simulator. They are identical, except that TUNING applies only to the global portion of the grid and TUNINGL to the LGRs, if any. TUNINGL applies all the set criteria to all of the LGRs i.e. all the LGRs must have the same timestepping and convergence criteria. The default timestepping and convergence criteria are different for global grids and LGRs because LGRs usually have much smaller grid cells and much higher throughputs than global cells. ECLIPSE does not simulate continuous periods of time. Output takes place at each DATES or TSTEP keyword; the interval between these keywords is subdivided into a number of timesteps. The timestep length is determined internally by ECLIPSE. The user can only regulate the timestep length by altering TUNING. The keyword syntax is TUNING <parameters> / <parameters> / <parameters> / and TUNINGL is similar. All three forward slashes must be specified even if the contents of one or more records remain defaulted. Non-Default TUNING Parameters The default values have been arrived at after more than a decade of experience and altering them is not necessary for the vast majority of problems. Altering TUNING can significantly increase the time required by the simulation and may even cause convergence problems. Situations in which non-default TUNING may, however, be necessary include: - Radial single well models. The innermost annulus of cells is likely to have a very low pore volume, i.e. the throughput of the cell may be large. Saturation changes are likely to be large over a timestep, so the minimum timestep length may need to be reduced. Well tests. Most well tests, especially DSTs have a very short duration, sometimes less than an hour. To model the frequent rate changes with sufficiently high temporal resolution the timesteps need to be very short, perhaps on the order of fractions of a minute. The
- 412. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 412 of 499 08/04/99 minimum timestep length will need to be reduced accordingly; the maximum timestep length may also need adjustment. Abrupt rate changes. When an action such as shutting in or opening a high rate well takes place, a sharp transient is generated which rapidly alters the flow patterns in the vicinity of the well. It may be necessary to reduce the timestep size and tighten the convergence criteria for a short period afterwards. Refer also to the chapter on Convergence, p.467for more information on choice of timestepping and convergence criteria. If convergence problems are being experienced, altering TUNING is unlikely to provide a solution. NEXTSTEP NEXTSTEP governs the length of only the following timestep (not reporting interval), which begins at the next DATES or TSTEP keyword. It is often used when a drastic action is taken such as shut-in or opening of a high rate well. In these circumstances the flow patterns and pressure gradients in the vicinity of the well change abruptly. In most cases ECLIPSE will reduce the timestep sizes automatically to cope with the change, but it may be necessary in some case to reduce manually the timestep immediately following the change.
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- 414. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 414 of 499 08/04/99 Output Control : RPTSCHED and RPTRST Figure 132: Output control using RPTSCHED • RPTSCHED is used to specify data written to the print file (.PRT) and the log file (.LOG) during the simulation • RPTSCHED governs the type and frequency of restart file output • RPTRST governs the frequency of restart files output and their contents. • Many quantities can be reported using either RPTRST or RPTSCHED. SCHEDULE RPTSCHED ’RESTART=2’ / TSTEP 10*180 / Outputs MODEL.X0001 to MODEL.X0010 --inclusive at 180 day intervals RPTRST ’BASIC=3’ ’FREQ=2’ / TSTEP 10*180 / Outputs MODEL.X0011, MODEL.X0013, --MODEL.X0015, MODEL.X0017, MODEL.X0019 --at 360 day intervals.
- 415. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 415 of 499 08/04/99 Output Control : RPTSCHED and RPTRST The output from the SCHEDULE section consists of various information written to the print (and optionally log) files, .PRT and .LOG plus periodic output of restart data. Restart data is used for either or both of two purposes: • To analyse simulation results on a cell-by-cell basis. Detailed discussions on how to analyse simulation results are beyond the scope of this course although tuition in the GRAF post-processor is an integral part of learning how to use ECLIPSE. • To initialise a simulation from the end of a previous simulation. This is discussed in the section on “Restart” p.312 The data in the PRT and LOG files is always ASCII, man-readable data and is generally in tabular form and falls into two categories: information which exists for every cell and tabular data. Examples are cell pressure and saturation, and well reports containing well flows, connection flows and layer flows, respectively. The restart data is written to the restart files. It is binary by default but may be formatted if the FMTOUT keyword is used in the RUNSPEC section. The restart data contains a complete description of the state of the model each reporting step and contains the following, among other data: • Pressure of each cell • If the model is three-phase, water and gas saturation as well as Rs for each cell. If the model contains wet gas then Rv is also included • If the model is two-phase, water or gas saturation for each cell plus the fixed Rs or Rv values. • Well location and completion data. This is the contents of WELSPECS and COMPDAT. • Group hierarchical structure. • Group and region cumulative flows. • Interblock flows (i.e. flows from cell to cell), fluids in place and phase potentials may optionally be written to the restart file. The restart data can be requested using two alternative formats. Both are valid and may be used in the same run RPTSCHED --Pre-95a fixed format. Current Versions of Eclipse still read this --1 2 3 4 5 Comment identifying position of items --Zero value requests no output of data for that item
- 416. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 416 of 499 08/04/99 --Request cell GOR in item 5 0 0 0 0 1 --Request restart at every report time in item 7 --Request well report in item 9 0 2 0 5 0 --Request solution summary and CPU information in items 11 and 12. 1 1 0 0 1 / Default everything else i.e. no output or RPTSCHED --More modern mnemonic-style output requests. ‘RS’ ‘RESTART=2’ ‘WELLS=2’ ‘SUMMARY’ ‘CPU’ ‘NEWTON’ / The first version requests output by integer parameters in specific positions; the second, more modern, uses mnemonics. The inverted commas are required. The seventh item or the RESTART mnemonic governs the frequency of restart output. This will be affected by the output style; restart information is written in a different manner if the file is unified or non-unified. The function of this mnemonic is: ‘RESTART=1’. Restart data is written at every report step. If the files are non-unified only the last one is kept; previous restart files are deleted. This reduces the disk space used. If the files are unified all of the restart data is preserved ‘RESTART=2’. Restart data is written at every report step and is kept whether the output is unified or non-unified. ‘RESTART=3’. As for ‘RESTART=2’ but interblock flows are added to the restart data ‘RESTART=4’. As for ‘RESTART=3’ but current fluids in place and phase potentials are added to the restart data. This keyword interacts in a complex manner with the RPTRST keyword. Refer to the ECLIPSE 100 REFERENCE MANUAL for a full description of RPTRST. NOTE. The first restart file is numbered one, e.g. MODELNAME.X0001. Restart file zero corresponds to the initial conditions in the model set either by equilibration, enumeration or a previous restart. Output of this file is requested with the RESTART mnemonic of the RPTSOL keyword (SOLUTION section). There must be at least one timestep (i.e. a TSTEP or DATES keyword) in the SCHEDULE section for restart file to be produced at time zero.
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- 418. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 418 of 499 08/04/99 Re-Solution and Re-Evaporation Rates: DRSDT & DRVDT Figure 133: Effect of zero gas re-solution rate DRSDT • The default re-solution rate of free gas into oil is infinity • The default re-evaporation rate of oil into gas is infinity • This applies within grid cells as well as to injected gas • These may be reduced if a mechanism is present to slow the processes • These should never be set to zero. A zero value means that the composition of the fluids can only change in one direction B DRSDT=0 DRSDT=∞ A
- 419. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 419 of 499 08/04/99 Re-Solution and Re-Evaporation Rates: DRSDT & DRVDT Under laboratory conditions gas comes out of solution when oil is subjected to pressure lower than the bubble point. If the pressure is raised without releasing any of the free gas, it re-dissolves into solution. DRSDT governs the rate of this re-solution only. It does not affect the rate of liberation of gas from oil below the bubble point. In reservoir conditions this can be represented by path A in Figure 133, which is reversible. This is equivalent to blowdown below the bubble point followed by re-pressurisation back to the initial pressure by injecting all of the produced gas back into the reservoir. If DRSDT is set to zero, the oil under reservoir conditions follows path B under the same scenario of blowdown and repressurisation. The gas does not re-dissolve in the oil, but remains free. This property is not described anywhere else in the ECLIPSE data file. In practice, DRSDT should never be set to zero. Gas resolution is, however, rarely instantaneous in practice, so DRSDT should not be set to the default value of infinity. In practice, engineers choose a value of DRSDT consistent with the observed re-solution rate. The significance of DRVDT is very similar, but applies to condensation and retrograde condensates. By default oil condensate evaporates instantly if the pressure is raised above the dew point and retrograde condensates evaporate if the pressure is dropped below the dew point. A zero value of DRVDT prevents this re-evaporation. Finite values of DRVDT are the norm and DRVDT should never be set to zero.
- 420. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 420 of 499 08/04/99 Simulation Advance and Termination: DATES, TSTEP & END Figure 134: Simulation advance and termination • The simulation start is at the beginning of the START keyword date in RUNSPEC. • DATES advances the simulation to the beginning of the day specified • TSTEP advances the simulation by a set number of days (hours in LAB units). • ECLIPSE advances the simulation by timesteps which length is chosen automatically • If using TSTEP the last of these timesteps will finish at the beginning of the set date • If using DATES the last of these timesteps will finish at the end of the final day • Output as requested in RPTSCHED will be generated at this time • Actions defined between two DATES or TSTEP keywords are effective from the date of the first, not the second • If using TSTEP during a history match, insert the actual date as a comment • END finishes the simulation and is compulsory. It does not have to be the last keyword, which eases editing problematic datasets DATES 1 JAN 1998 / Advance to 12:00 am on 1/1/98 1 JUN 1998 / Advance to 12:00 am on 1/6/98 / TSTEP 1 / Advance to 12:00 pm on 2/6/98 TSTEP 0.2 / Advance by 0.2 days END Conclude simulation
- 421. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 421 of 499 08/04/99 Simulation Advance and Termination: DATES, TSTEP & END TSTEP and DATES are the only keywords that may be used to advance the simulation through time. Any number of records terminated by a forward slash may follow the DATES keyword; a blank record (i.e. forward slash) then terminates the keyword itself. TSTEP is followed by a series of intervals measured in days; multiple values are allowed. No more than fifty are allowed in any one TSTEP keyword; fifty-one will cause an error. The SCHEDULE section is the only part of the dataset in which the order of the keywords is crucial. ECLIPSE advances the simulation from the start date to the first DATES or by the first TSTEP. Any actions following those keywords, such as workovers, shut-ins, TUNING changes etc., are read from the data file. Those actions take effect immediately, i.e. from the beginning of the second TSTEP or the end of the first DATES. In general DATES is easier o use during a history match because the well flow rates are known accurately over precise periods. Measured flow rates are also reported at precise times and dates, which often makes DATES more suitable than TSTEP. The END keyword is used to terminate the simulation and can be located anywhere in the SCHEDULE section.
- 422. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 422 of 499 08/04/99 Well Performance Matching Figure 135: Physical and Eclipse Models of Production Wells • Drainage radius defaults to pressure equivalent radius in ECLIPSE • Pressure equivalent radius depends on grid block size in ECLIPSE • Drainage radius from well testing may be much bigger than grid cell size • The well productivity or injectivity needs to be modified to reflect this • Drawdown is measured from grid block to well in ECLIPSE • Drawdown in the reservoir is measured from grid block to drainage radius • Corrections need to be made to well inflow performance equation to compensate for this. Pw Pw Pc, cell pressure P* average reservoir pressure rd re Physical Model Eclipse Model Pw, well BHP rd , re drainage radii
- 423. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 423 of 499 08/04/99 Well Performance Matching The well inflow performance is strongly affected by the choice of well parameters, notably the productivity index and drawdown. In the Eclipse well model these are estimated from grid block properties by default and may be quite inaccurate. It is a significant part of history matching to adjust the well parameters to achieve the correct inflow performance. Productivity Index Adjustment For a single completion, the productivity index for phase p is often written S r r cKh B K J w dpp rp p + = ln θ µ EQ. 87 Where: rd the well drainage radius rw is the wellbore radius and the remaining symbols have their usual meanings. In ECLIPSE this is replaced by default by S r r cKh B K J w epp rp pe + = ln θ µ EQ. 88 or ( ) ( ) + + = S r r S r r JJ w d w e pep ln ln EQ. 89 Where re is the pressure equivalent radius derived from the connecting grid block. The drainage radius rd is specified in the 7th item of WELSPECS. If it is defaulted the productivity index Jp used by Eclipse is equal to Jpe. Otherwise, if the engineer sets an explicit value of the drainage radius, the Eclipse default is replaced by that calculated in EQ. 89.
- 424. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 424 of 499 08/04/99 Drawdown Adjustment For a single completion the inflow performance relationship for phase p is often written ( )HPPJQ wpp +−= * EQ. 90 Where P* is the average reservoir pressure Pw the well BHP H the hydrostatic head between the datum point and the connection In ECLIPSE this is replaced by ( )HPPJQ wcppe +−= EQ. 91 Where Pc is the pressure of the connecting cell and the productivity index has already been adjusted. It follows that to match the observed performance the ECLIPSE productivity index in EQ. 91 must be further multiplied by a factor given by HPP HPP wc w +− +−* EQ. 92 There is no automated provision for this in ECLIPSE; the engineer has to estimate the factor from measured and/or simulated pressures and simulated productivity indices. Relevant quantities output by Eclipse are the summary vectors WBP, WBP4, WBP5 and WBP9. These are illustrated in Figure 136 and defined below.
- 425. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 425 of 499 08/04/99 Figure 136: Measures of Pressure in the Vicinity of a Well WBP is the pressure of the connecting cell WBP4 is the average pressure of the cells diagonal with respect to the connecting cell WBP5 is the average of WBP4 and WBP WBP9 is the average of WBP5 plus the cells neighbouring the connecting cell Each of these is corrected to the datum depth. Therefore, at any particular time the productivity index multiplier is, approximately, HWBHPWBP HWBHPWBP +− +−9 EQ. 93 WPI1 is the well productivity based on the value of WBP WPI4 is the well productivity based on the value of WBP4 WPI5 is the well productivity based on the value of WBP5 WPI9 is the well productivity based on the value of WBP9 This is applied at specific times during a history match using the keyword WPIMULT. WBP WBP4WBP9 WBP4 WBP4 WBP4 WBP9 WBP9WBP9 I J
- 426. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 426 of 499 08/04/99 Manual Workovers, Rate and PI Modifications Figure 137:A selection of manual workover keywords • Workovers in the History matching period take place at known times; they are manual and input by the engineer • Workovers in prediction mode are usually automatic and are carried out by ECLIPSE to satisfy physical and economic constraints. • Only Manual workovers are discussed here. --Open and shut wells at known times WELOPEN --Alter completion properties COMPDAT --Alter partial completions COMPRP, COMPVE --Alter well rate and pressure targets WELTARG -- WCONHIST --Modify Well PI WELPI, WPIMULT --Change cell transmissibility "MULT" family
- 427. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 427 of 499 08/04/99 Manual Workovers, Rate and PI Modifications Manually Opening and Shutting Wells or Connections: WELOPEN WELOPEN is a manual workover keyword WELOPEN closes or opens entire wells or specific connections previously specified with WELSPECS and COMPDAT To open a well and one or more of its connections, use two records – one for the well, one for the connections. Completion Workovers: COMPDAT COMPDAT defines the locations and properties of connections COMPDAT can be used at any stage after WELSPECS to modify or shut existing connections or open new ones Refer to Connection Specification: COMPDAT on p.384 for a full description of the keyword Partially Penetrated Completion Workovers: COMPRP, COMPVE COMPRP is used to define connections that partially penetrate grid cells COMPRP should only be used in models with dispersed flow, i.e. in which the VE option has not been activated. COMPRP must follow WELSPECS and COMPDAT COMPRP can be used at any point following WELPSPECS and COMPDAT to modify connection properties. Refer to the section titled “Partial Completion: COMPRP”, p.392 for a full description COMPVE is used to define connections that partially penetrate grid cells in models using VE COMPVE must follow WELSPECS and COMPDAT COMPVE can be used at any point following WELPSPECS and COMPDAT to modify connection properties. Refer to the section titled “Partial Completion with VE: COMPVE”, p.396 for a full description Modifying Well Targets: WELTARG WELTARG may supplement any of WCONHIST, WCONPROD, WCONINJ and WCONINJE WELTARG must follow one of these keywords Each record of WELTARG modifies a flow target i.e. a rate or a pressure constraint
- 428. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 428 of 499 08/04/99 WELTARG applies to producers or injectors There is no limit on the number of target rates that may be modified using WELTARG Producers and injectors can be specified in a single instance of WELTARG To modify more then one phase for a given well use separate records Well Pi Modification: WELPI and WPIMULT WELPI is used to explicitly set the productivity or injectivity of a well WELPI is most likely to be used for setting a PI measured from well tests WPIMULT multiples the current well PI by a set factor WPIMULT is more likely to be used in history matching to improve PI while dealing with other reservoir characteristics During history matching the PI has to be big enough to allow the well to produce at the specified rate without reaching the BHP limit. WPIMULT is cumulative unless connection factors are reset between two instances of WPIMULT COMPDAT will reset the WPIMULT value to 1.0 WELPI and WPIMULT must not be applied to a well at the same time i.e. there has to be a DATES or TSTEP keyword between them. Modelling Well Stimulation by means other than Skin Factor Change The ‘MULT’ keyword family can be used to modify transmissibility in the SCHEDULE section. Refer to the section on “Transmissibility modification ”, p.184 for a description of their usage. Since the cell properties have been converted to pore volume and transmissibility in the earlier GRID section, directly modifying the permeability is not allowed in the SCHEDULE section The ‘MULT’ keyword family does not affect the well connection factor; only the transmissibilities between neighbouring cells are altered To model stimulation of a well by means other than reducing the skin factor in COMPDAT, other workarounds need to used In a radial model the cells corresponding to I=2 i.e. the second ring of cells around the well, may be given altered transmissibilities. This effectively introduces altered permeabilities in the near-wellbore region, but not at the wellbore.
- 429. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 429 of 499 08/04/99 In any model, selected completions may be closed using COMPDAT, the well PI modified and the closed connections re-opened. This should take place over a relatively short time.
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- 431. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 431 of 499 08/04/99 THE SCHEDULE SECTION – PREDICTION
- 432. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 432 of 499 08/04/99 Prediction SCHEDULE Section Structure Figure 138: Structure of the SCHEDULE section in prediction mode • Many of these keywords are also used in history matching • Figure 138 shows a fairly comprehensive list of available prediction mode keywords • They should be inserted into the dataset in the order shown • This section deals with keywords that are not used in history matching • Keywords VPFPROD, VFPINJ, WELSPECS, COMPDAT, WCONINJ, WCONINJE, WELPI, WPIMULT, TUNING, TUNINGL, NEXTSTEP, RPTSCHED, RPTRST and END have been described in the section titled “The SCHEDULE Section – History Matching”, on p.357 --VFP tables for THP control VFPPROD, VFPINJ --Well and completion definition, inc. infill wells WELSPECS, COMPDAT, COMPRP, COMPVE --Production well targets WCONPROD, WELDRAW --Injection Well Targets WCONINJ, WCONINJE --Activate new wells as necessary QDRILL, WDRILTIM, WELSOMIN --Well PI Specification WELPI, WPIMULT --Automatic workover specification WCUTBACK, WORKLIM, WORKTHP, --Auto. work over specification contd. COMPLUMP, WPLUG --Place wells on pump or gas lift WLIFT --Periodic testing of shut wells WTEST --Time taken to perform automatic workovers WORKLIM --Well and completion economic limits CECON, WECON, WECONINJ --Tolerance for economic limits and targets WLIMTOL --Group hierarchical structure GRUPTREE --Distribute production amongst wells GCONPROD, GUIDERAT, WGRUPCON --Distribute amongst wells contd. PRIORITY, WELPRI --Distribute injection mongst wells GCONINJE, GUIDERAT, WGRUPCON --Distribute injection amongst wells contd. PRIORITY, WELPRI, WINJMULT --Satellite production and injection GSATPROD, GSATINJE --Group and field economic limits GECON --Simulator control parameters TUNING, TUNINGL, NEXTSTEP --Output control RPTSCHED, RPTRST --Simulator advance and termination DATES, TSTEP, END
- 433. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 433 of 499 08/04/99 Prediction SCHEDULE Section Structure The means of entering VFP tables and defining wellhead locations and completions are the same for prediction mode as for history matching mode. If the prediction dataset is a restart run all of the surface facilities and well definitions in force during the history match are already in place. This information is contained in the restart file. VFP tables are not stored in restart files. If VFP tables are to be used in a restart run, they have to be explicitly contained in the dataset. If the VFP table allocation changes at the end of the history match, the WELSPECS and/or GRUPNET keyword needs to be used at the beginning of the prediction. Any wells that turn from production to injection or vice versa need to altered as follows: • Reset the main flowing phase using WELSPECS. • Shut the well in using WCONPROD. Declare it as a SHUT well; do not simply set the rate to zero. • Define the injection rate targets using WCONINJ or WCONINJE. The converse applies for turnaround of injectors to producers. During the prediction phase ECLIPSE is required to calculate well rates subject to any other operational constraints. Wells are usually operated in one of two ways: • To produce as long as possible before going on to decline • To produce at their maximum rates for as long as possible. The way the well behaves depends on the control mode and whether it is subject to control from a superior level in the field hierarchy. This means that the well may be required to produce subject to constraints from downstream facilities such as gas handling plants or water knock-out plants. The simplest individual well controls are by either rate or pressure. If no production rate target is specified the well will produce as much as possible for as long as possible and will always be on decline. The well is said to be under pressure control i.e. operates subject to a BHP or THP limit If a target rate is specified the well will produce at the specified rate for as long as possible. Once the BHP or THP of the well reaches the pressure limit, the well will go on decline. The well is under rate control until the time it goes on decline, at which time it switches to pressure control.
- 434. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 434 of 499 08/04/99 The productivity index controls the time at which wells go on decline, which is why the BHP needs to be matched at the end of the history match. If a well is not operated correctly there will be a production discontinuity at the end of the history match or beginning of the prediction. The well will also change control mode. Typical rate controls are: • Oil rate control • Gas rate control • Water rate control • Liquid rate control • Voidage rate control If a well is under rate control this means that the well has been allocated a production target. If a well cannot produce at the target rate it will continue to produce under rate control provided it does not reach a pressure limit. If a well cannot produce at the target rate and reaches a limiting pressure it will be switched to pressure control using the constraints as the target value Typical pressure control modes are: • Tubing head pressure (THP) control • Bottom-hole pressure (BHP) control • Drawdown pressure control If a well is under pressure control it means that ECLIPSE will try to produce or inject at that set pressure or drawdown. Pressure control is usually used during predictions as it is not generally appropriate for history matching. For a well under pressure control, ECLIPSE has to calculate the rate. If the calculated rate exceeds the rate limit, the well will be moved to rate control using the rate limit as the target rate. Wells under THP control must have a VFP table.
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- 436. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 436 of 499 08/04/99 Setting Well Target Rates: WCONPROD Figure 139: The WCONPROD keyword • WCONPROD is used to allocate rate and pressure targets for producers in prediction mode • The rates are used as upper limits • Only simulated rates are reported • The rates are specified for many reporting periods, often at monthly intervals • WCONPROD cannot precede COMPDAT • WELTARG can be used to modify production targets after WCONPROD WCONPROD --1 2 3 4 5 --Well Open/ Control Oil Water --Name Shut Mode Rate Rate P1 OPEN ORAT 3000 1* --6 7 8 9 10 --Gas Liquid Reservoir BHP THP --Rate Rate Volume Limit Limit -- Rate 1* 1* 1* 2500 / --11 12 --VFP ALQ --Table --Record of data for well P21 P21 OPEN ORAT 2000 1* 1* 1* 1* 2500 / /
- 437. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 437 of 499 08/04/99 Setting Well Target Rates: WCONPROD WCONPROD is the most flexible keyword for setting the constraints for individual production wells. The default values for the possible control modes for production as well as injection wells are summarised in the table below Mode Production Well Default Injection Well Default BHP Atmospheric pressure Infinity THP Atmospheric pressure Infinity Oil Rate infinity Infinity Water Rate Infinity Infinity Gas Rate Infinity Infinity Liquid Rate Infinity Not Applicable Reservoir Volume Rate Infinity infinity Group Rate Fraction of group or field rate as determined by GCONPROD Fraction of group or field rate as determined by GCONINJE In order to produce the well control mode must be defined. One of the control modes should be chosen depending on which fluid accounts for the main production, or else either or both pressure limits. A value must then be set for the corresponding rate or pressure target. The values of the remaining rate and pressure targets can be defaulted or else assigned limits as required. The control mode can only be defaulted if the well is shut or stopped and is not in the drilling queue. ECLIPSE will govern the well flow according to the control mode chosen, provided that the limits on the other quantities are observed. Figure 140 represents the production from a 2D cross-section model with edge drive from a medium strength aquifer located some distance from the only production well and downdip. A water injector located downdip and operating at 2600 psi provides additional pressure support. The quantities reported are: • well oil production rate WOPR • well water production rate WWPR • well BHP WBHP • ell control mode (WMCTL) versus time.
- 438. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 438 of 499 08/04/99 Figure 140: Example of the effect of WCONPROD The production constraints for well P1 are set as shown in Figure 140. • well P1 is initially under oil rate control and remains so until approximately 1600 days. Its production potential is more than adequate to produce at this oil rate. During this period the water cut is steadily rising and the BHP dropping • At approximately 1600 days the BHP has reached the lower limit of 3000 psi. The advancing waterfront has reached the well but is not yet providing enough pressure support to raise the well BHP above 3000 psi. The well is moved to BHP control. • The BHP remains at 3000 psi while the water front advances. The oil production drops, water cut rises. • At approximately 2500 days the water production reaches the upper limit of 2000 stb/day. The well is switched to control by water rate. This is permitted because in so doing the BHP remains at least 3000 psi. WCONPROD -Well Open/ Control Qo Qw Qg Ql Qresv BHP THP -Name Shut Mode P1 OPEN ORAT 4000 2000 1* 1* 1* 3000 /
- 439. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 439 of 499 08/04/99 • Thereafter until approximately 3500 days the water production rate remains fixed, the oil production rate continues to decline and the BHP rises. The BHP is increasing because pressure support is still being received at the producer from the aquifer and injector. • At around 3500 days the pressure support is seen to decline at the well. The BHP drops steadily while the water production remains fixed at 2000 stb/day until 14,000 days • At 14,000 days the BHP has again reached the lower limit of 3000 psi. The aquifer and injector cannot maintain the pressure support and the well is switched to BHP control. • Water production declines steadily to the end of the simulation at 18,000 days. • No economic limits have been specified so there are no workovers or shut-ins.
- 440. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 440 of 499 08/04/99 Economic Limit Definition Figure 141: Application of economic limits • Economic limits may be applied at connection, well, group of field level • The actions taken when a limit is reached depend on the workover procedure specified in the relevant keyword • Different keywords are used at connection, well and field/group level. These are discussed in later sections. • Economic limits and automatic workovers are closely related; one triggers the other. Economic Limits can be applied to: éOil production rate Lower limit éGas production rate Lower limit éWater cut Upper limit éGas-oil ratio Upper limit éWater-gas ratio Upper limit The tests can be applied to: éField/ group production GECON éWell production WECON éIndividual connections (ratios only) CECON
- 441. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 441 of 499 08/04/99 Economic Limit Definition Economic limits are a means of altering the production policy in order to satisfy financial and facilities constraints. Financial calculations are not performed; the limits are applied to physical quantities such as oil rate and GOR. When an economic limit is reached, a range of actions can be taken depending on the level at which the limit is applied. These are summarised in Figure 142. Figure 142: Actions taken on violating economic limits • These actions take place at the beginning of the timestep following breaching of the economic limit and are usually referred to as automatic workovers. The various types of available workover are: • Do nothing - NONE • Shut the worst-offending connection - CON • Shut the worst-offending connection and all below it - +CON • Plug back the well from top or bottom – PLUG. See also “Plugging Wells Back: WPLUG”. Action Field/ Well Connect- Group ection Do Nothing? Yes Yes No Stop run? Yes Yes No Shut in if rate limit broken? Yes Yes N/A Open another well if rate limit broken? Yes Yes N/A Workover worst completion/well on exceeding a ratio? Yes Yes Yes Apply 2dary water cut limit on shut-in? No Yes No
- 442. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 442 of 499 08/04/99 Well Economic Limits, Automatic Workovers and Cutbacks Figure 143: A selection of automatic workover keywords • Automatic workovers are performed by ECLIPSE during prediction • They are intended to satisfy economic and physical production and injection constraints • WECON, WECONINJ and CECON invoke automatic workovers when wells or completions become uneconomic • The section on “Manual Workovers, Rate and PI Modifications” on p.426 discusses other types of workover --Economic Limits --Producer economic limits WECON --Injector economic limits WECONINJ --Connection economic limits CECON --Single well workover keywords:- --Group connections together COMPLUMP --Plugging back a well WPLUG --Time taken for automatic workover WORKLIM --Workover procedure if a well dies under THP control WORKTHP --Change VFP table and / or ALQ (retube and /or lift or pump) WLIFT --Periodic well test WTEST --Pressure-dependent injectivity multiplier WINJMULT --New well activation keywords:- --Set up drilling queue QDRILL --Set drilling duration WRILTIM --Minimum cell oil saturation for automatic opening WELSOMIN --Cycle wells on and off e.g. as in WAG processes WCYCLE --Cutbacks --Cut back producers and injectors WCUTBACK --Calculate oil rate from last month’s average GOR WGROPEN
- 443. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 443 of 499 08/04/99 Well Economic Limits, Automatic Workovers and Cutbacks ECLIPSE contains a large range of facilities for working over individual wells, setting economic limits and adjusting well rates by various means. This section describes the major features of some of the more commonly used facilities of this kind. The descriptions are not exhaustive; refer to the ECLIPSE 100 REFERENCE MANUAL and ECLIPSE 100 TECHNICAL APPENDICES for more comprehensive descriptions. Well Economic Limits Figure 144: The WECON keyword • WECON is used to have ECLIPSE automatically perform workovers and shut the well in when necessary • Workovers are performed when the water cut, GOR, OGR or rate limits breach the specified limiting values for the well • A workover is then performed automatically at the beginning of the next timestep • Once connections or wells are shut in they remain shut by default. • Wells can be re-opened by periodic testing using WTEST WECON --1 2 3 4 5 --Well Minimum Minimum Maximum Maximum --Name Oil Gas Water GOR -- Rate Rate Cut ’P*’ 1000 1* 0.5 1* --6 7 8 9 10 --Maximum Workover End Follow- Economic limits --WGR Procedure Run? On well apply to rates or -- name potentials? 1* CON NO / / --11 12 13 --Secondary Workover Maximum --Water cut proc. for Gas-liquid --limit 2ndary limit Ratio
- 444. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 444 of 499 08/04/99 • Wells can be re-opened if a secondary water cut limit is specified in WECON • The simulation run can be legally terminated if a well breaches an economic limit • Wildcards in the well name can be used to apply the economic limits to a number of wells • Workovers can take place if group economic limits are breached. Refer to the GECON keyword for more information. Connection Economic Limits: CECON Figure 145: The CECON keyword • CECON defines the economic limits for individual connections • CECON cannot precede COMPDAT • If connections are lumped together using COMPLUMP they must all be subject to the same limits in CECON. CECON -- 1 2 3 4 5 -- Well I J K1 K2 -- Name -- 6 7 8 -- Maximum Maximum Maximum -- WCT GOR WGR
- 445. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 445 of 499 08/04/99 Plugging Wells Back: WPLUG Figure 146: Plugback using WPLUG • When a well is subject to automatic plug-back a certain length of perforations is closed • Plug-backs alter the connection depths so the ratios of produced fluids changes in a VE run • If VE is not active the new perforation depths are converted into scaled saturation table endpoints • WPLUG sets the lengths of perforation that are closed off when wells are plugged back • Plugging back is one of the workover options in WECON, CECON, GCONPROD, GCONPRI, GCONSALE and WORKTHP. WPLUG -- 1 2 3 -- Well Length closed Length closed -- name from top from bottom -- on plug-back on plug-back
- 446. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 446 of 499 08/04/99 Workovers using WLIFT Figure 147: The WLIFT keyword for retubing wells • WLIFT performs a switching operation when one of the limits is reached • The switching operations are changing THP limit, VFP table (re-tubing) and changing ALQ (lifting or compressing) • WLIFT also defines the order in which the switching options are executed • The Production Rules also perform switching operations on breaching set limits. Refer to the PRORDER keyword. WLIFT --1 2 3 4 5 --Well Min Phase New New --Name Rate VFP -- Table ALQ --6 7 8 9 -- New Max New Max -- Efficiency WCT THP GLR -- Factor Limit
- 447. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 447 of 499 08/04/99 Well Testing: WTEST Figure 148: The WTEST keyword for well testing • By default wells or completions are not re-opened after closure • WTEST is used to regularly test wells with a view to re-opening them. • WTEST may reopen wells closed for physical and / or economic reasons. WTEST --1 2 3 --Well Test Closure --Name Interval reason --4 5 --Max Startup --Tests time
- 448. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 448 of 499 08/04/99 Cutting Wells Back: WCUTBACK Figure 149: The WCUTBACK keyword • WCUTBACK can be applied to producers and injectors. • Whenever one of the upper or lower limits is violated the target of the nominated phase is either reduced or increased. • When a well is cut back its control mode changes to the mode of the phase in item 7 • Because the target rate is re-defined after WCUTBACK takes action, the rate can exceed limits set in other keywords such as WCONPROD • To avoid this choose a phase for which no limit has been set elsewhere WCUTBACK --1 2 3 4 5 --Well Max Max Max Maximum --Name WCT GOR GLR WGR --6 7 8 9 10 --Cut-back Phase to Limiting Limiting Min --Factor Cut back Grid block Grid block WCT -- Pressure for Pressure for -- cut-back reversing -- cut-back -- --11 12 13 --Minimum Minimum Minimum --GOR GLR WGR
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- 450. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 450 of 499 08/04/99 Group Control Figure 150: Controlling production for a group of wells • Wells can be collected into groups • Wells are placed in groups using the WELSPECS keyword • Production of a group of wells is controlled using the GCONPROD keyword • Injection of a group of wells is controlled using the GCONINJE keyword • Producers and injectors should not be placed in separate groups • The FIELD group is always present • Wells are placed under group control by specifying the well control mode as GRUP in WCONPROD or WCONINJE Well Field Group
- 451. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 451 of 499 08/04/99 Group Control Collective control occurs when the flow target of a well depends directly on the flow rates of other wells. This is most commonly when injection rates are dependent on production volumes. Common types of group control include • Group / field production control. The overall oil, water, gas or liquid production rates are given specific targets at group and / or field level. The wells produce in proportion to a guide rate, subject to obeying their own rate and pressure limits. The guide rate defaults to the well production potential. • Re-injection. The injectors are set to re-inject a specific fraction of the stock tank water or gas production of a group or of the entire field. • Voidage replacement. Enough water or gas is injected to replace all or a specified fraction of the field or group voidage production. Voidage production is the deficit produced by injecting less fluid than is produced. It is expressed in terms of reservoir volume, so oil, water and gas cannot be separated. • Priority control. The overall oil, water, gas or liquid production rates are set at group and / or field level. Wells are opened in decreasing order of their priority until the overall target is met. Each well flows at its maximum rate except for the last one opened. The priority is either set explicitly or calculated periodically based on the ratios of phase flows.
- 452. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 452 of 499 08/04/99 Creating a Group Hierarchy: GRUPTREE Figure 151: The GRUPTREE keyword • Groups can belong to parent groups • Group hierarchy is defined using GRUPTREE • There is no limit to the number of levels in the hierarchy • A group may contain either wells or groups, but not both. GRUPTREE --1 2 --Son Father
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- 454. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 454 of 499 08/04/99 Group / Field Production Control: GCONPROD Figure 152: The GCONPROD keyword • Group production controls may apply to groups and / or the field • Target phase production rates are set • Production is apportioned between subordinate groups and wells according to their guide rates GCONPROD --1 2 3 4 5 --Group Control Oil Rate Water Rate Gas Rate --Name Mode Target Target Target FIELD ORAT 5000 1* 1* --6 7 8 9 10 --Liquid rate Workover Higher level Guide Guide rate --Target Procedure Control? Rate Phase 1* CON / / --11 12 13 --Proc. on exceeding Proc. on exceeding Proc. on exceeding --Water rate limit Gas rate limit Liquid rate limit
- 455. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 455 of 499 08/04/99 Group / Field Production Control: GCONPROD For a group or the field, a control mode is defined and targets are set for oil rate, water rate, gas rate and liquid rate. The targets are apportioned between subordinate groups in proportion to their guide rates. The group guide rate defaults to the sum of production potentials of the wells belonging to the group. The production rate targets are apportioned between wells in the same way as for groups. The controls are set using the GCONPROD keyword. NOTE. No well or group may violate its own rate or pressure limits. Groups and wells can be allocated set guide rates so that they contribute a specific proportion of a higher level target. For example, field oil rate target may be shared between groups in proportion to their liquid handling capacities. Guide rate may also be calculated periodically from the formula ( ) ( )FD A p p RERCB POT GR 21 )( ++ = EQ. 94 Where the coefficients A to F are entered using the keyword GUIDERAT. R1 and R2 are ratios of phase potentials, which depend on the nominated phase p.This formula is used if the guide rate definition in item 10 of GCONPROD is set to FORM. Individual well guide rates for group control may be set using the WGUPCON keyword. Production Target Infringements If a group / field cannot meet its production target, well in the drilling queue can be opened automatically, subject to the limits set in WDRILTIM, in an effort to maintain the production. If a group / field upper limit is exceeded a range of options are available: • Do nothing • Work over the worst offending well. If the violated target is a control target, then subordinate wells are cut back sufficiently to ensure the group rate target is observed. If the violated target is not a control target, a workover is applied to the worst-offending well. The worst offending well has the highest ratio of violating phase to the well’s preferred phase. • Close the worst offending well.
- 456. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 456 of 499 08/04/99 • Impose group / field production rate control at the violated limit. This amounts to cutting back subordinate wells sufficiently to ensure that the group target rate is honoured. If the violated target is a control target, then subordinate wells are cut back sufficiently to ensure the group rate target is observed. • Different workover procedures can be selected for individual phases on failing to meet a production target. Solution Method The order in which ECLIPSE solves for produced and injected fluids within a single group is • Solve for the production of any well operating at its control target • Share the remainder of the group’s target among the wells under group control in proportion to their guide rates. • If a well violates one of its own flow or pressure limits, take it out of group control and operate it at the violated limit. • Repeat if necessary. At field level the procedure is similar: Any group solved as above Production is solved for first by default. This allows the injection to be calculated afterwards, as opposed to estimated. The procedure is performed for the first NUPCOL Newton iterations
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- 458. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 458 of 499 08/04/99 Group Injection Control: GCONINJE Figure 153: The GCONINJE keyword • Group injection controls may apply to groups and / or the field • Target phase injection rates are set • Injection is apportioned between subordinate groups and wells according to their guide rates GCONINJE --1 2 3 4 5 --Group Phase Control Surface Reservoir --Name Mode Injection Volume -- Injection -- Target Target FIELD WAT VREP 1* 1* --6 7 8 9 10 --Re-injection Voidage Higher Guide Guide --Fraction Replacement Control? Rate Phase -- Fraction 1* 1 / /
- 459. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 459 of 499 08/04/99 Group Injection Control Injection group guide rates are similar to production guide rates. Defaulted group guide rates are set equal to the sum of injection potentials of subordinate wells and groups. There is no equivalent to the FORM option (see Group / Field Production Control: GCONPROD, p.454) for calculating production guide rates. Group injection controls and limits can be set using GCONINJE according to one of the following modes. Surface Injection Rate The injection rate of any phase at surface conditions Reservoir Volume Injection Rate This is the total reservoir volume injection rate of all injected phases. Re-injection In re-injection mode the group/field surface injection rate of the nominated phase will be controlled to equal the group/field production multiplied by a re-injection fraction. For the gas phase, any gas consumed by subordinate groups is first subtracted from the production rate. Voidage Replacement If the production consists of Vo stb of oil, Vw stb of water and Vg Mscf of gas, the total reservoir production V is ( ) )()()()( PBPRVVPBVPBVV gsogwwoo −++= EQ. 95 And the surface volume injection of water required to balance the production is )(PB V V w w =′ EQ. 96 While the surface volume of gas required is )(PB V V g g =′ EQ. 97 The pressure used to calculate the PVT parameters of the reservoir fluids is either the field hydrocarbon pore volume weighted average pressure or the average pressure of the
- 460. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 460 of 499 08/04/99 fluid-in-place region specified in the WELSPECS keyword. The field hydrocarbon pore volume weighted average pressure is given by ∑ ∑ − − = i iw pore i ioiw pore i SVi PSV P )1( )1( , ,, EQ. 98 Where Po,i is the cell oil pressure obtained at the previous timestep. The field injection of the top-up phase can be shared between groups in proportion to their net voidage rates. The net voidage is voidage production minus reservoir volume injection of the other injected phases. There can only be one top-up phase during the simulation.
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- 462. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 462 of 499 08/04/99 Priority Control Figure 154: Priority control keywords • Wells are allocated a priority • Wells are opened and brought on stream in decreasing order of priority until the group target is reached • All wells flow at their maximum rates except for the last one opened • All wells of lower priority remain shut in PRIORITY Calculate well priority numbers --1 2 3 4 5 6 7 8 9 --Calc Interval A B C D E F G H WELPRI Set priority number if not calculated from PRIORITY --1 2 --Well Name Priority Number GCONPRI Set group targets under priority control --1 2 3 4 5 --Group Oil rate Proc. on Water rate Proc. on --Name Limit Exceeding oil Limit Exceeding water -- Rate limit Rate limit ---6 7 8 9 10 11 --Gas rate Proc. on Liq. Proc. on Resv Balancing. --Limit Exceeding gas Rate limit Exceeding liq. Rate Fraction --- Rate limit Rate Limit Limit Limit GRUPTARG Re-set group production rate target or limit under priority control --1 2 3 --Group Target New --Name Definition Target
- 463. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 463 of 499 08/04/99 Priority Control Under prioritisation wells are opened one by one in order of decreasing priority until the group production rate target is met. All rates flow at their maximum rates. The last well to be opened is choked back to provide exactly the production required. This well is not subject to the economic constraints in WECON. Lower priority wells remain stopped or shut as defined in WELPSECS. Wells closed by the user or by automatic workovers are not available for prioritisation. Prioritisation is performed every NUPCOL iterations and can be used in the same dataset as group control. Priorities will be calculated periodically from the formula gwo gwo HQGQFQE DQCQBQA P +++ +++ = EQ. 99 None of the coefficients A-H may be negative and at least one of A-D and one of E-H must be non-zero. The priority equation provides a means of emphasising a specific character of production. For instance if A=D=E=F=H=0 and B=C=G=1 then the priority is w wo Q QQ P + = EQ. 100 That is, inverse water cut. The priority numbers calculated from EQ. 99 may be overwritten or supplemented by the WELPRI keyword. If the priority number is greater than zero, it will override the value calculated in EQ. 99. If the number supplied to WELPRI is negative, it will be overwritten by the value from the priority equation. The priority number must not be zero.
- 464. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 464 of 499 08/04/99 Group Economic Limits: GECON Figure 155: The GECON keyword • Groups unable to produce the minimum required will be subject to workovers • The available workovers are the same as for WECON GECON --1 2 3 4 5 --Group Min Min Max Max --Name Oil rate Gas rate Water cut GOR FIELD 600 / / --6 7 8 9 --Max Workover End Max --WGR Procedure Run? Open wells
- 465. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 465 of 499 08/04/99 Group Economic Limits: GECON If a group or field under group control violates the maximum water cut, GOR or WGR or the minimum oil or gas production rates. The workover options available are: • NONE, do nothing • CON, shut the worst-offending connection in the worst-offending well • +CON, shut the worst-offending connection and all below it in the worst-offending well • WELL, shut or stop (see WELSPECS) the worst-offending well • PLUG, plug back the worst-offending well. The run may optionally be terminated if all the producers are shut or stopped provided that at least one producer has been opened previously. The limit on the number of open wells subordinate to this group prevents wells from being opened automatically. That is, wells specified as AUTO in WCONPROD, WELOPEN, WCONINJE) or form the drilling queue (QDRILL) will not be opened if they are subordinate to this group. This will not affect manual opening of wells i.e. OPEN in WCONPROD, WCONINJE etc.
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- 467.
- 468. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 468 of 499 08/04/99 Typical Convergence Problems Figure 156: A typical convergence problem report • Convergence problems have typical symptoms • Convergence reports will help to identify the cause • Convergence problems are almost always related to one of the following • Data Error • Typographic Errors • Model Design • An entire chapter of the ECLIPSE 100 TECHNICAL APPENDICES is devoted to interpretation of convergence reports. @--WARNING AT TIME 0.0 DAYS ( 1-JAN-1997): @ LINEAR EQUATIONS NOT FULLY CONVERGED - RUN MAY GO FASTER @ IF YOU INCREASE LITMAX (= 25 - TUNING KEYWORD) @--PROBLEM AT TIME 0.0 DAYS ( 1-JAN-1997): @ NON-LINEAR EQUATION CONVERGENCE FAILURE @ ITERATION LIMIT REACHED - BUT TIME STEP @ ACCEPTED BECAUSE IT IS TOO SMALL TO CHOP. STEP 1 TIME= 2.40 HOURS ( +2.40 HOURS CHOP 12 ITS) (1-JAN-1997) PAV= 333.8 BARSA WCT=0.051 GOR= 644.15 SM3/SM3 WGR= 0.0001 SM3/SM3 PR.RATE PR.TOTAL IN.RATE IN.TOTAL MAX SATURN CHANGE MAX TIME TRNC ERR OIL 6000. 600. 0. 0. -0.780( 3, 1, 20) -0.780( 3, 1, 20) WAT 321. 32. 0. 0. 0.580( 6, 1, 19) 0.580( 6, 1, 19) GAS 3864881. 386488. 0. 0. 0.780( 2, 1, 21) 0.780( 2, 1, 21) MAX DP = -315.55( 1, 1, 24) MAX DRS=********( 1, 1, 24) @--WARNING AT TIME 0.1 DAYS ( 1-JAN-1997): @ LINEAR EQUATIONS NOT FULLY CONVERGED - RUN MAY GO FASTER @ IF YOU INCREASE LITMAX (= 25 - TUNING KEYWORD)
- 469. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 469 of 499 08/04/99 Typical Convergence Problems The aim of this section is describe the symptoms of a typical convergence problem, explain how to interpret convergence reports and outline the most common causes of convergence problems and how they can be remedied. Figure 156 shows a section of the PRT file containing typical convergence failure messages. Typical causes are summarised in Figure 157. Figure 157: Typical causes of convergence problems Data Error The vast majority of convergence problems are caused by data error. These can usually be traced to one of the following, although more esoteric data errors are not unknown. PVT Table Errors PVT data is stored internally in ECLIPSE as 1/B and 1/Bµ. If the simulator is operating beyond the range of the PVT data provided, ECLIPSE extrapolates the PVT table. This might happen, for instance, if the BHP of an injection well is greater than the maximum pressure to which the PVT data is defined. Small variations in 1/B and 1/Bµ will lead to é Data Error é PVT tables é VFP curves é Saturation functions é Special Characters & missing values é Model design é Grid geometry é Small PV cells next to large PV cells é Dual poro Fracture cell PV << Matrix cell PV é LGRs é LGR smaller than drainage radius é Initial contacts outside LGR é Innermost cells in radial LGR too small é Program defects
- 470. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 470 of 499 08/04/99 large variations in their reciprocals, which can lead to calculation of unphysical PVT properties. To check whether ECLIPSE is extrapolating PVT or VFP tables insert the following anywhere near the beginning of the SCHEDULE section EXTRAPMS 3 / PVT data tables must be smooth. Since ECLIPSE interpolates linearly between the given data points an infinite gradient at any point will cause convergence difficulties Note also that PVT data may be extrapolated into regions of negative compressibility. This is not reported as it lies outside the range of the data provided in the PVT tables. Regions of negative compressibility could also exist in the range of the PVT tables. ECLIPSE only tests the compressibility at 30 points between the minimum and maximum saturated pressures. There may be intermediate points of negative compressibility, especially if the range of pressures is large VFP Table Errors ECLIPSE extrapolates VFP curves linearly in any dimension if required. As with any form of extrapolation, the results cannot be guaranteed to be physically correct. VFP curves should be designed to ensure that every dimension spans the operating regime the well is expected to encounter. The following EXTRAPMS 3 / will print a message on the last extrapolation performed by ECLIPSE in both the PVT and VFP tables. Where VFP curves cross there are two possible THP values at a given flow rate, GOR and WCT in an oil well. Since ECLIPSE solves for THP iteratively, this is certain to cause convergence problems if the well operates near one of THPs at which the curves cross. Crossing VFP curves may be legitimate if, for instance, BHP values have been set artificially high to indicate supersonic flow or flow at speeds in excess of the erosion velocity limit. Crossing curves may be detected quickly and easily by reading the VFP tables from an ECLIPSE data file into the VFPI program. The section named VFP Table Supervisor contains a button for checking for crossing curves. Saturation Table Errors Highly sloping relative permeability curves i.e. large changes in relative permeability over small saturation range are likely to cause convergence problems. The problem may be precipitated or worsened by endpoint scaling. To examine relative permeability
- 471. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 471 of 499 08/04/99 tables use EPSDEBUG or RPTSOL to output the data. Note that if endpoint scaled curves need to be examined visually within GRAF, the selected endpoint scaling method must be the same as that used by ECLIPSE. Typographic Errors A small proportion of convergence problems result from typographic errors in the input data file. Missing values The ECLIPSE input parser identifies input data by the position of a number or string within each keyword. Hence the significance of explicitly entering default values as 1* when they are followed by non-default values in a keyword. For instance the following two examples of PVTO are not identical: PVTO –Rs Pbub Bo µo 1.500 4000 1.12 0.94 1.600 4400 1.13 0.92 4800 1.1255 0.92 / / PVTO –Rs Pbub Bo µo 1.500 4000 1.12 1.600 4400 1.13 0.92 4800 1.1255 0.92 / / In the second example the viscosity of oil at 4000 psi with an Rs of 1.5 is 1.6 cP. In the first example, it is 0.94 cP. A simulation using the latter, incorrect, PVTO keyword may even run without experiencing convergence problems, although the results will be incorrect. This is unlikely but by no means rare. Special Characters The tab (→) and control (^) characters cause input data to be read incorrectly. They are often found in the SCHEDULE section, where users have created bespoke programs for manipulating well data and have imported tab-delimited text into ECLIPSE. As with missing data, by the nature of this type of error ECLIPSE cannot provide a warning message.
- 472. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 472 of 499 08/04/99 Model Design A few convergence problems are model design related. Common problems include Grid Geometry If adjacent cells have a pore volume ratio greater than approximately 1000:1 it is likely that the large cell will determine the flow behaviour of the small cell. The smaller cell saturation may fluctuate wildly and be in practice impossible to calculate. In such cases the grid should be modified or the offending cell deactivated. Cells having a flow over the duration of a timestep that is many times greater than the cell pore volume pore volume are likely to experience convergence problems. Such cells are often found near pinchouts, local grid refinements and radial models. In radial models and radial LGRs they are usually found near the wellbore where INRAD and OUTRAD have been defined but the radius of the innermost annulus of cells has been calculated by ECLIPSE. This radius can be very small – on the order of centimetres. LGR Design If an LGR does not extend beyond the drainage radius of the well around which it designed, there will be a discontinuity in the pressure distribution in the radial direction. During the course of solving LGRs a great deal of data is passed between the global and local grids; if this is inconsistent or not smooth, convergence errors are likely to result. Note that the well drainage radius can be increased by giving it a large negative skin. The solution is to extend the LGR horizontally. If a fluid contact should meet the upper or lower face of an LGR, it is invaded by another phase. When data is transferred between the LGR and the underlying global host cell, the phase mixtures are different although the LGR and host cell occupy the same position. The solution is to extend the LGR vertically so that it crosses any contacts from the beginning of the simulation. Program defects No software can be guaranteed to be bug-free; ECLIPSE is a sophisticated piece of software by comparison with many others and it is not possible to test every combination of options ECLIPSE under every conceivable circumstance in the time available. Nevertheless, experience shows that due to an extensive pre-release testing cycle which incorporates the results of previous test cycles, program defects account for a very small proportion of convergence problems
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- 474. ECLIPSE 100 USERCOURSE EXERCISES
- 475. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 475 of 499 08/04/99 Exercise 1: Single Well Coning Model Figure 158: Single Well Coning Model Purpose • To acquaint the user with editing ECLIPSE data files • To compare several simulation models in GRAF
- 476. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 476 of 499 08/04/99 Exercise 1: Single Well Coning Model Part A: Introduction. 1 This is a radial model of a single oil production well. The reservoir contains oil and free and dissolved gas; there is an initial gas cap. In the course of production the well initially produces only oil but eventually cones gas. Four different models of the case are presented RAD04.DATA, RAD08.DATA, RAD16.DATA and RAD24.DATA. RAD.GRF is a run file you will need at a later stage of this exercise. RAD04 is a complete data set; do not alter it. Each of the others contains a different error in the RUNSPEC section. The errors need to be identified and corrected before the models can be run and the results compared. Do not alter any sections of the data file except RUNSPEC i.e. do not change anything after the GRID keyword. Part B: Obtain data files. 1 Your course tutor will provide the files you need. Copy them all from the course directory to a convenient location in a sub-directory of your home directory. Part C: Run the RAD04.DATA simulation 1 To do this type @eclipse at the command prompt. When prompted for the filename enter RAD04; the suffix .DATA is not required. All other options may be defaulted (i.e. just type the RETURN key. If you are using a PC run the GEOQUEST launcher, select ECLIPSE and choose the directory in which the copied files have been placed. Note that RAD04.DATA generates no errors Part D: Run RAD08.DATA 1 Run this in the same way as for RAD04.DATA. Inspect the file RAD08.PRT in the text editor of your choice. There is an error in the RUNSPEC section of the data file. Find the first ERROR message in the PRT file and identify the cause. Edit RAD08.DATA to correct the error. Re-run RAD08.DATA. Part E: Run RAD16.DATA and RAD24.DATA 1 Repeat the previous portion of the exercise for files RAD16.DATA and RAD24.DATA. Part F: Using GRAF 1 The only difference between the models is that each contains different numbers of cells. To examine the results, run the GRAF program by typing @graf at the
- 477. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 477 of 499 08/04/99 command prompt. If you are using a PC, activate the GEOQUEST launcher if it is not already running, select GRAF and choose the directory the data resides in. 2 From within GRAF type 0.8.2 and supply the file name RAD when prompted. Then type 0.5.1 to view the results one picture at a time. 3 If you find that the results for one or more runs are missing, examine the output from the simulation runs for errors and make any changes you need to the data files. Rerun the simulations and ensure that the ECLIPSE output is unified. 4 To view the results within GRAF a second time you do not need to exit GRAF. From within GRAF type 0.6.6.5 to clear the workspace. Then run the Graphics Run File (GRF) RAD as before. Part G: Comment on the differences between the four models. 1 Since the models are identical except for the numbers of cells in the radial and vertical directions, why is gas breakthrough observed at different times in the simulation?
- 478. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 478 of 499 08/04/99 Comments on Exercise 1: Single Well Coning Model Breakthrough times are different for each model The breakthrough time depends on the numbers of cells in the radial and vertical directions The gas production profile is also different for each model For sufficiently small cells the breakthrough time and profile reach limiting values The radial models are an example of the effects of numerical diffusion. As the simulations progress, saturation fronts move from one cell centre to the next. In models with large cells, saturation changes jump a large distance compared to models with smaller cells in the same time, hence the varying breakthrough times. The breakthrough times do not appear to vary monotonically with cell number. This is because the models are being refined in two dimensions. The shape of the gas production profiles also varies. Consider the cell centres of two adjacent cells in RAD04.DATA. The relative permeability between these points is as given in the data file. Gas may flow from one to the other once the critical gas saturation has been reached in one cell. Consider the same two points in a more refined model. Gas will flow between the two points when the critical gas saturation is reached at the destination cell. By the time this happens; the gas saturation of some of the other cells will be considerably greater than critical. Thus, the overall relative permeability between the same two points in a more refined model is not the same as in RAD04.DATA.
- 479. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 479 of 499 08/04/99 Exercise 2: Sector Model RUNSPEC Section Figure 159: Model dimensions Purpose • To create a RUNSPEC section from scratch Fetkovich aquifer provides edge drive at I=20 and J=5 faces. Uppermost and lowermost model faces are no-flow boundaries K I J 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 K=1 to 10 ZX plane at Y=0 and YZ plane at X=0 are no-flow boundaries inside the reservoir.
- 480. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 480 of 499 08/04/99 Exercise 2: Sector Model RUNSPEC Section Part A: Introduction 1 In order to investigate the efficiency of water injection as a production mechanism for a particular field it has been decided to perform a simulation study of a representative sector of a reservoir (see Figure 159). The geological information about the reservoir in this area of the field indicates that there are ten reservoir layers. Seismic data indicates that there is a large aquifer attached to the field. 2 The sector represents one quarter of a faulted anticlinal structure. Symmetry considerations suggest that the other three sectors behave similarly. So, the sector model can be studied in isolation and the results applied to the field as a whole. The sector model boundaries are taken to be no-flow boundaries. In order to justify estimates of future production calculated using ECLIPSE, the model must first be history matched. The first stage of this process is to construct a simulation model suitable for matching. Part B: Model Dimensions 1 Based on the amount of data available and the computer resources, it has been decided to carry out the simulation using a 3D model comprising 10 simulation layers, corresponding to the 10 geological layers, and with 20 columns of cells in the lateral direction and 5 rows of cells in the transverse direction. The aquifer volume will be modelled by an analytical aquifer (Fetkovich). There are two producers and one injector. Up to two infill wells may be drilled at a later date. Part C: Fluid Properties 1 The reservoir oil is initially undersaturated and the reservoir will be produced in such a way that the fluid remains above bubble point pressure everywhere at all times. The fluid properties are believed to be constant throughout the reservoir. Part D: RUNSPEC section 1 Using the editor of your choice, create the RUNSPEC section appropriate for the simulation model described above. Request unified output. 2 Choose a START date for this simulation of 1st January 1994. 3 Insert the remaining major section keywords 4 Ensure the data file is named CP.DATA. 5 Save it in a convenient location in a subdirectory of your home directory.
- 481. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 481 of 499 08/04/99 Exercise 3: Sector Model GRID Section Figure 160: Basic model layer data Purpose • To provide reservoir geometry descriptions in block-centred and corner point styles and examine the differences between them using GRAF • To provide basic rock properties for both geometries. Layer Thickness Horizontal Permeability (ft) (mD) 1 32 10 2 22 5 3 20 100 4 4 2000 5 32 200 6 4 2000 7 26 100 8 26 50 9 4 2000 10 28 50 φ = 25% throughout the reservoir Kv/Kh=0.04 everywhere
- 482. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 482 of 499 08/04/99 Exercise 3: Sector Model GRID Section Part A: Create the grid in corner point form 1 The data in Figure 160 has been obtained from wells drilled throughout the reservoir. The file CP.GRDECL contains the model geometry in corner point form. Use it together with part of the above data to complete the GRID section of CP.DATA. Request output of the grid geometry (.GRID file), static reservoir properties (.INIT file) and the X-direction transmissibilities and all non-neighbour connections (.PRT file). You will need to ensure the cross-section has been constructed correctly. To do this:- • Go to the directory containing CP.DATA • Run ECLIPSE from the command prompt by typing @eclipse • Follow the prompts. Note that the input filename is not case-sensitive and the suffix .DATA or .DAT should be excluded. 2 From within GRAF run the graphics run file named HM.GRF and view the results. Convince yourself that the model geometry and properties have been correctly defined. Part B: Create the block centred equivalent 1 Copy CP.DATA to BC.DATA. Remove the corner point geometrical description from BC.DATA 2 Create the block centred equivalent with the help of information from Figure 160, Figure 161 and Figure 162. Consider carefully the cell TOPS definitions. Calculate the TOPS for cells in Figure 161 and Figure 162 and assume the slopes of the model in XZ and YZ are fixed. 3 Run the simulation of BC.DATA and compare the geometrical description to CP.DATA within GRAF. Note especially the differences between the cell-to-cell connections and transmissibility values across the fault. Part C: Compare the two geometries 1 Which geometrical description do you consider to be more realistic?
- 483. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 483 of 499 08/04/99 Figure 161: XZ model section at Y=0 X(ft) Z(ft)
- 484. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 484 of 499 08/04/99 Figure 162: YZ model section at X=0 Y(ft) Z(ft)
- 485. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 485 of 499 08/04/99 Exercise 4: Sector Model PROPS and REGIONS Sections Figure 163: Sector Model PROPS Section Construction Purpose • To supply and verify reservoir fluid PVT properties • To supply and verify relative permeability and capillary pressure data • To define the distinct reservoir regions
- 486. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 486 of 499 08/04/99 Exercise 4: Sector Model PROPS and REGIONS Sections Part A: Fluid PVT and Rock Compressibility Data 1 PVT analysis indicates the reservoir oil to have a bubble point of 2500 psia. The bubble-point solution GOR is 656 scf/stb and formation volume factor is 1.26 Rb/stb. The oil viscosity is constant at 0.5 cP. The oil compressibility Co is 6x10-6 (psi)-1 . At surface conditions the oil API gravity is 32° and the specific gravity of reservoir water is 1.05. Relative to air the gas gravity is 0.7. The water formation volume factor Bw is 1.03 rb/stb at 4000 psia (the initial reservoir pressure at 7000 ft) with constant water viscosity µw 0.4 cP and compressibility 3x10-6 (psi)-1 . The rock compressibility is 3.5*10-6 (psia)-1 at the initial reservoir pressure. Update the PROPS sections of both CP.DATA and BC.DATA with the above information. Note that ( ) ( ) ( )bubo buboo PPC ePBPB −− = EQ. 101 Part B: Rock Data 1 From special core analysis the following data has been obtained Sw Krw Kro Pcw 0.2 0.00 0.90 4.0 0.3 0.05 0.75 2.0 0.4 0.10 0.55 1.0 0.5 0.18 0.30 0.5 0.6 0.28 0.10 0.2 0.7 0.40 0.00 0.1 1.0 1.00 0.00 0.0 Update the PROPS sections of both CP.DATA and BC.DATA with the above information. EQ. 102 2 Create two fluid-in-place (FIP) regions, one for each fault block, using the FIPNUM keyword. Create additional fluid-in-place regions, one for each layer, named FIPLAYER. Update the REGIONS sections of both BC.DATA and CP.DATA Remember to update the RUNPSEC sections as necessary. 3 Run both the BC.DATA and CP.DATA simulations Verify that the saturation functions and PVT data are correct. File HM.GRF contains commands to do this.
- 487. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 487 of 499 08/04/99 Exercise 5: Sector Model Initialisation Figure 164: Sector Model Initialisation Purpose • To supply initial conditions for model equilibration • To supply aquifer definition
- 488. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 488 of 499 08/04/99 Exercise 5: Sector Model Initialisation Part A: Equilibration Information 1 From the results of wells drilled throughout the reservoir the OWC has been determined as 7150ft. This is coincident with the free water level. Use centre block equilibration (EQUIL item 9 = 0). Part B: Aquifer Specification 1 The seismologist has estimated that the aquifer attached to the cross-section is formed by lateral and transverse extension of the reservoir and contains approximately 10MMMbbl (1010 bbl) of water and could supply this at a rate of 50bbl/day/psi. 2 Create the appropriate SOLUTION section for both BC.DATA and CP.DATA using the above information. Request output of a restart file at time zero. Part C: SUMMARY Data Output 1 Take note of the summary vectors required by HM.GRF and ensure these are present in the SUMMARY sections of BC.DATA and CP.DATA Part D: Initial Restart file Output 1 Request output of a restart file at the time of initialisation. Remember to advance the simulation by at least one timestep by inserting the following into the SCHEDULE section: - TSTEP 1 / END 2 Update BC.DATA and CP.DATA. Part E: Model Stability 1 Copy CP.DATA to STABLE.DATA and request output of field average pressure and field aquifer flow rate. Add the following into the SCHEDULE section:- TSTEP 20*30 / 2 This will run STABLE.DATA for 600 days with no production or injection. Run the simulation and view the results within GRAF using HM.GRF. Comment on the stability of the simulation.
- 489. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 489 of 499 08/04/99 Part F: Improved Accuracy Options 1 Make a note of the initial fluid in place in STABLE.DATA. This will be available in the PRT file as a report on FIELD TOTALS if fluid in place output has been requested with the RPTSCHED keyword. Modify the equilibration options to use tilted block equilibration with twenty sub-layers and ensure that quiescence and mobile fluid correction options are active. Rerun the model STABLE.DATA and compare the initial fluids in place to the version using centre block equilibration. Is the difference significant?
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- 491. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 491 of 499 08/04/99 Exercise 6: Sector Model History Match Figure 165: Sector Model History Matching Purpose • To adjust model properties to match the simulation to measured production
- 492. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 492 of 499 08/04/99 Exercise 6: Sector Model History Match Part A: Well data 1 Two vertical oil producers have been drilled in the sector, at (2, 2) and (8, 1) in I and J. they are named P1 and P21, respectively. There is a single vertical water injector named I20 at (20, 1). The producers are completed in each reservoir layer but the injector is completed only in the upper five layers. All wells have an internal diameter of 0.583 feet. Part B: Historical Well rates and workovers 1 The measured well rates throughout the history period are: • Well P1 3000 stb/d • Well P21 2000 stb/d • Well I20 8000 stb/d 2 All workovers during the production history are shut-ins of individual connections. The dates at which individual connections are shut in are given in the following table. Date Well P1 25th Oct 1996 2, 2, 9 23rd March 1997 2, 2, 8 11th April 1997 2, 2, 10 1st May 1997 2, 2, 6 24th June 1997 2, 2, 7 3 Wells P21 and I20 are not worked over during the production history. The history matching phase is complete on 1st July 1997. 4 Create the SCHEDULE section up to 1st July 1997 from scratch for datasets BC.DATA and CP.DATA. Request restart file output at every reporting step. Request also output of fluid in place regions, detailed well reports, CPU usage and a summary of the convergence of the Newton iteration. 5 Compare the results of simulations BC.DATA and CP.DATA using HM.GRF. Can you explain the differences? Part C: Sensitivity analysis 1 In this part of the exercise, model CP.DATA will be matched to the measured production. The measured phase production rates can also be examined using
- 493. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 493 of 499 08/04/99 HM.GRF. These are the line plots for model CP_M. The first stage of the history match is to establish in what way individual model features affect model performance. There is a degree of uncertainty in the aquifer initial volume and productivity index. You will need to adjust each value individually, run each simulation, and note whether the performance improves or worsens compared to CP_M. Use the initial volumes and PI values in the following table and make a note of the results. Aquifer Initial volume (109 stb) Improves/Worsens? 0.01 10 10,000 Aquifer PI (stb/day/psi) 5 50 500 Part G: History Matching 1 Complete the match by selecting the combination of aquifer volume and PI that match CP.DATA to the CP_M model. You will need to run a number of simulations to find the right combination. Every possible combination of the suggested aquifer volumes and PIs is available in the following table. At this stage in the exercise, however, you should be able to eliminate some of them. Use the table to mark combinations you have discounted and systematically examine the results from the remaining combinations. Initial Volume (stb) 10E6 10E9 10E12 5 50 Productivityindex (stb/day/psi) 500 2 Make certain that you have output a restart file at the conclusion of the history match on 1st July 1997.
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- 495. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 495 of 499 08/04/99 Exercise 7: Sector Model Recovery Optimisation Figure 166: Sector Model Recovery Optimisation Purpose • To optimise oil recovery by simulating several production scenarios
- 496. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 496 of 499 08/04/99 Exercise 7: Sector Model Recovery Optimisation Part A: Production Prediction 1 Copy CP.DATA to PRED.DATA and extend the simulation until 1st January 2002. Convert PRED.DATA to a restart run using the output from the conclusion of the history match. 2 From experience from other fields in the area production ceases to be economic when well water cut reaches 50% or the oil production drops below 1000 stb/day. In addition the surface facilities require the following well constraints: Well Max Rate BHP Limit P1 3000 stbo/day 2500 psia P21 2000 stbo/day 2500 psia I20 8000 stbw/day 4500 psia 3 Use the graphics run file PRED.GRF to examine the results Part B: Recovery optimisation 1 Copy PRED.DATA to NOINJ.DATA and remove the water injector. Analyse the results. Is further water injection justified? Alter PRED.DATA as appropriate. You should find that the injector helps keep the up-dip producer open for an extra six months. 2 In order to provide a more satisfactory overall production profile, it has been decided to operate the reservoir under group control. In addition to the well constraints described above, the following group controls will be applied at field level: • Field oil rate: 5000 stb/day maximum, 600 stb/day minimum. • Water injection: Variable to maintain 100% voidage replacement Copy PRED.DATA to PRED_G.DATA and edit it as appropriate. Run the simulation and examine the results. Comment on the improvement. 3 Copy PRED_G.DATA to PRED_OPT.DATA. Optimise the recovery by drilling up to two infill wells and selecting the most suitable perforation and work-over policy.
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- 498. 6FKOXPEHUJHU Eclipse 100 UserCourse Page 498 of 499 08/04/99 REFERENCES [1] Huppler, J. D.: “Numerical Investigation of the Effects of Core Heterogeneities on Waterflood Relative Permeabilities”, SPEJ (Dec 1970) 381-92; Trans., AIME, 249 135 [2] Mattax, C. C., Dalton, R. L: “Reservoir Simulation”, SPE Monograph v.13, 1990 135 [3] Mattax, C. C., Dalton, R. L., “Reservoir Simulation”, SPE Monograph v.13, 1990 137 [4] Stone; Trans AIME, 249, 1970, pp.214-218 255 [5] Stone; J. Can. Pet. Tech., 12, 1973, 53-61 255 [6] Odeh. J. Pet. Tech. 1980, p.964 392 [7] M. Munoz, Eclipse 100 User Course passim 397
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