Snorre's FAWAG field trial matched with Phenomenological model for foam using CMG STARS software

1. Mobility Control Using Foam
Snorre/WFB FAWAG Pilot Revisit
Arif Ali Khan (NTNU), Ying Guo (Total E&P Norge),
Dag Wessel-Berg (SINTEF), Jon Kleppe (NTNU), Dennis Coombe (CMG)

2. Content
• Introduction
– Project motivation and scope
• Snorre WFB pilot simulation – a revisit
– Updated reservoir model
– Porting from ECLIPSE to STARS and model validation
– Full-field model vs sector model
– Simulation benchmarking
• Simulation of FAWAG pilot
– Sensitivity study with respect of foam parameters
• Summary, conclusions and recommendations

3. Introduction
• Project motivation
– Start out as a master thesis
– New Snorre reservoir model established in 2005
– Evaluate STARS as field simulator for FAWAG
• Project scope and ambition
– Transfer the most recent reservoir model for Snorre WBF pilot to
STARS simulator
– Re-evaluate the foam effect on the new Snorre WBF model
– Establish a feasible workflow for FAWAG simulation
– Recommend potential improvement for STARS simulator

4. A feasible workflow for FAWAG simulation
• Assumptions
– Most of the FAWAG project will likely be implemented after a significant
period of water or gas flooding, and the oil saturation in the flooded
areas is around Sorw or Sorg
– The reservoir model is well established
• Pre FAWAG simulation
– Full-field simulation before FAWAG using Eclipse
– Establish a sector model for the pilot region and validate using Eclipse
• FAWAG simulation (field + sector)
– Port the models from Eclipse to STARS
• Use Petrel to export the grids, rock property, faults etc to STARS + manual
adjustment of the data file for STARS
• Use Eclipse simulated saturation and pressure map before the FAWAG start
to initialize the STARS simulation
– History-match the FAWAG data or predict the field behaviour using
STARS

5. Snorre WFB pilot - history
• Pilot time: November 1999 –
2001
• Wells involved:
– P32 (inj)/P39 (prod), 1550 m
– P32 (inj)/P42 (prod), 1450 m
• 2 FAWAG cycles after gas
injection and WAG operation
for about 3 years
• Total surfactant injected:
~140 tonn
– Slug 1: 15262 SM3 (0.49
wt%) for 9,5 days followed
by 100 days gas injection
– Slug 2: 31733 SM3 (0.2
wt%) for 20.3 days followed
by more gas injection
• Ref: SPE 75157 by A.
Skauge et.al.

6. WAG/FAWAG history (well pair P32-39)
1. Surf slug: 0.49 wt%, 9.5 days, 15262 SM3 2. Surf slug: 0.20 wt%, 20.3 days, 31733 SM3
WAG FAWAG WAG

7. Snorre reservoir

8. From Eclipse to STARS
STARS
WFB – Full Field (2005 –
Statoil)
ECLIPSE
WFB – sector (This work)

9. Establish the sector model for FAWAG using
Frontsim
Water injection
Gas injection
Effect from nearby wells
Selected sector

10. SPE75157 vs this work
Geological Differences
• Stochastic perm / porosity
• Faults
PVT
• Composional - 4 Component
• Black oil - 5 Component
Rock Compressibility
Foam
• Part never matches with old
parameters versus new
model
New Eclipse Type Well
Section
• New well Index
• Deviated
• Trans and skin included
Absolute
Permeability
Porosity
FAULTS

11. SPE75157 vs this work
Lay
er
#
division
s
K
(md)
Ф Layer
height
(m)
Layer
height
(mD*M)
4.2 14 700
2 480
1 120
610
6.2
14.0
12.2
S1 5 3500 0.259
S2 7 400 0.236
S3 5
1
80
90
0.225
0.191
P- 39
Pdummy
P-32
25x21x20 = 10 500 grid blocks
P-32
P- 42
P- 39
Lay
er
#
division
s
K
(md)
Ф Avg
layer
height
(m)
Layer
height
(mD*M)
1.69 -
-
S3 8 - - 4.06 -
S4 6 - - 4.06 -
2.77
S1 4 - -
S2 16 - -Stochastic
values
29 x 26 x 34 = 25 636 grid blocks

12. Model porting from Eclipse to STARS
• Grid data – Use Petrel to export files with STARS format
(trivial)
– Grid coordinates and faults
– Permeability and porosity values for each blocks
– Transmissibility multipliers for each blocks
– Pressure + Saturation values for each blocks
• Fluid data – Manual entering to STARS input files (trivial)
• Well data - Convert Eclipse schedule files using with
CGM/IMEX to STARTS input files + 70% manual input
file adjustment (tedious)
• Add foam in STARS (trivial)
Arif – please review and
change to match what
you have done.

13. FAWAG pilot simulation workflow
Eclipse
Field model
S + P profile
in restart files
STARS
Field model
Field simulation
results including
foam effect
STARS
Field model
Eclipse
Field model
S + P profile
in restart files
Field simulation
results including
foam effect
WAG period FAWAG period

14. Eclipse vs STARS – Field model/NO FOAM
Poor match

15. Eclipse vs STARS – Field model/NO FOAM
FULL FIELD SNORRE WFB, STARS
P-39P (PRODUCER)
Water Oil Ratio SC MEASURED
Water Oil Ratio SC ECLIPSE
Water Cut SC STARS
Water Cut SC STARS
Time (Date)
WaterOilR
1997 1998 1999 2000 2001 2002
0.00
0.20
0.40
0.60
0.80
1.00
WAG FAWAG
SLUG-1
SLUG-2
FULL FIELD SNORRE WFB, STARS
P-39P (PRODUCER)
Water Oil Ratio SC MEASURED
Water Oil Ratio SC ECLIPSE
Water Cut SC STARS
Water Cut SC STARS
Time (Date)
WaterOilR
1997 1998 1999 2000 2001 2002
0.00
0.20
0.40
0.60
0.80
1.00
WAG FAWAG
SLUG-1
SLUG-2
WAG FAWAG
SLUG-1
SLUG-2
Watercut

16. Eclipse vs STARS – Field model/NO FOAM
FULL FIELD SNORRE WFB, STARS
P-39P (PRODUCER)
P-39P Blackoil, STARS
P-39P Compositional, STARS
WBHP_SIM_P-39P ECLIPSE
Time (Date)
Well
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
15,000
20,000
25,000
30,000
35,000
WAG FAWAG
SLUG-1
SLUG-2
FULL FIELD SNORRE WFB, STARS
P-39P (PRODUCER)
P-39P Blackoil, STARS
P-39P Compositional, STARS
WBHP_SIM_P-39P ECLIPSE
Time (Date)
Well
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
15,000
20,000
25,000
30,000
35,000
WAG FAWAG
SLUG-1
SLUG-2
WAG FAWAG
SLUG-1
SLUG-2
WellBoreholepressure(KPa)

17. Validation sector model
ECLIPSE vs STARS (no foam)
WAG FAWAG
SLUG-1
SLUG-2
WAG FAWAG
SLUG-1
SLUG-2
WAG FAWAG
SLUG-1
SLUG-2

18. Validation sector model
ECLIPSE vs STARS (no foam)
WAG FAWAG
SLUG-1
SLUG-2
WAG FAWAG
SLUG-1
SLUG-2
WAG FAWAG
SLUG-1
SLUG-2

19. Simulation benchmarking
• Full field model – Snorre
– No of grid blocks: XYZ= 43 x 146 x 34 => 213 452 grid blocks
– No of wells: 8 up to the end of FAWAG pilot
– Total simulation run time
• Eclipse* up to FAWAG: ~ 20 hours
• STARS** incl FAWAG ~ 18 hours
• STARS** for FAWAG only: ~ 6 hours
• Sector model
– No of grid blocks: XYZ= 29 x 26 x 34 => 25 636 grid blocks (~ 8 time
smaller than full field model)
– No of wells: 3 up to the end of FAWAG pilot
– Total simulation run time
• STARS** for FAWAG only: ~ 2 hours
* Unix / Solaris – 32 bits
** High-End PC (Pentium4, dual processor, 3GHz/1.5GB RAM), 32 bits

20. Foam simulation – phenomenological approach
• The physical phenomenon included in the sensitivity
studies
1. Necessary surfactant concentration in order for foam to grow
(fsurfmin)
2. Foam dry out when there is not sufficient water (Swmin)
3. Foam killed by surplus of oil (Sof)
4. Foam collapse due to viscous forces (Nc) – criticall capillary
number

21. Foam Model in STARS:
( ) FMskk w
o
rg
f
rg ×=
)1
1
654321 ⋅⋅⋅⋅⋅⋅⋅⋅⋅+
=
FFFFFFMRF
FM
• FM Dimensionless Interpolation Factor
FM = 1 (no foam)
FM = 0 (strong foam)
• MRF Reference mobility reduction factor
• F1 Surfactant concentration term
• F2 Water saturation term
• F3 Oil Saturation (foam killer)
• F4 Gas Velocity term
• F5 Capillary Number term
• F6 Critical Capillary Number term

22. Surfactant concentation effect
epsurf
s
fmsurf
w
F ⎥
⎦
⎤
⎢
⎣
⎡
=1

23. Water saturation effect on foam
⎥
⎦
⎤
⎢
⎣
⎡ −×
+=
π
)(arctan(
5.02
fmdrySepdry
F w

24. Oil saturation effect on foam
epoil
o
fmoil
fmoilS
F ⎥
⎦
⎤
⎢
⎣
⎡ −
=3
F3: Oil Saturation Effect on FM
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0.00 0.10 0.20 0.30 0.40 0.50
So
[FM]
0
200
400
600
800
1000
1200
0.000.050.100.150.200.250.30
Sw
MRF
FM- epoil = 0 FM- epoil = 0.25 FM- epoil = 1 FM- epoil = 2
fmoil = 0.25 Sw MRF = 1000
FoamStrengthDecrease
Foam
No Foam
No Foam
Foam

25. Capillary number term
epcap
cN
fmcap
F ⎥
⎦
⎤
⎢
⎣
⎡
=5
wg
c
PK
N
σ
∆
=
0,00
0,50
1,00
1,50
1,E-
10
1,E-
09
1,E-
08
1,E-
07
1,E-
06
1,E-
05
1,E-
04
1,E-
03
1,E-
02
1,E-
01
1,E+0
0
1,E+0
1
1,E+0
2
Nc
FM
0
200
400
600
800
1000
1200
MRF
FM- epcap = -1 FM- epcap = 0 FM- epcap = 0,5 FM- epcap = 1 FM- epc
F5: Relative Capillary Number
F5: Relative Capillary Number Effect Term
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E-10 1.E-09 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03
Nc
F5
epcap = -1 epcap = 0 epcap = 0.5 epcap = 1 epcap = 5 fmcap = 7.84E-08
epcap = 0
(Viscous Effects
Neglected on Foam
Strength)
Slope = -1
(shear Thinning)
Foam Degradation
Slope = +1
(shear
Thickening)
Viscous Forces

26. Relative Permeabilities – After Foam Application
After Foam
Before Foam

27. MRF sensitivity
MRF Sensitivity
SECTOR_WFB_MRF_10.irf
SECTOR_WFB_MRF_20.irf
SECTOR_WFB_MRF_50.irf
SECTOR_WFB_MRF_70.irf
SECTOR_WFB_MRF_100.irf
SECTOR_WFB_MRF_200.irf
SECTOR_WFB_MRF_300.irf
SECTOR_WFB_MRF_400.irf
Sector, No Foam
History
Gas Injection
Water Injection
Time (Date)
GasOilRatioSC(m3/m3)
GasRateSC(m3/day)
WaterRateSC(m3/day)
1998-12-1 1999-5-30 1999-11-26 2000-5-24 2000-11-20
0
200
400
600
800
0.00e+0
5.00e+5
1.00e+6
1.50e+6
2.00e+6
0
2,000
4,000
6,000
8,000
FAWAG
MRF = 50 (Ref SPE75157)
MRF =10
MRF =20
MRF >100

28. Oil saturation sensitivity on foam
Weak foam
Strong foam

29. Foam sensitivity on critical capillary pressure

30. Foam sensitivity on critical capillary pressure

31. Foam sensitivity on water saturation

32. Foam sensitivity on water saturation

33. Sensitivity study on foam
This work SPE 75157
Base case Scale of
influence
Base case
1 MRF ~10 - 50
fmdry = 0.12 – 0.2
fpdry = 50000 – 500
000
2
2
No done ins this
study. Not sure. (higly
dependent on
permeability.
3 for block-block
2 for well-block
Scale of
influence
Adsorption fmsurf = 0.0000058
(0.01 wt%AOS??)
epsurf = 1.0
4
Foam
strength
(MRF)
MRF = 70 1
Foam dryout fmdry = 0.6
epdry = 100
2
Oil tolerance fmoil = 0.2-0.3
epoil = 2
3
Shear
Thinning
fmcap = 7.0E-05
epcap = 1.5
N/A

34. Surfactant adsorption

35. Conclusions and recommendations
• The simulation exercises on the foam WFB FAWAG pilot
demonstrate the feasibility STARS as a tool for field scale studies for
FAWAG.
• More understanding and tuning of the reservoir simulation for
FAWAG is needed in order to obtain trust-while results.
• Acquisition of lab data must be designed closely related to the
planed field operation
• Refined grid analysis should be done in the close-well areas, but
STARS must be made more robust for this.
• Hysteresis for WAG period should be included in the simulations
• MRF as dependent on the FAWAG cycles, pressures, etc (input
table?)
• Oil saturation plays important role for foam behaviour, specially in
the saturation ranges where foam is likely to be generated or killed
and more sophisticated modelling is desired to capture the possible
phenomena, e.g. Sw and its distribution, wettability, oil composition.

36. Thanks for your attention !
Questions?