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  • 1. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Petroleum Reservoir Engineering ----Basic Concepts Pennsylvania 1859S.K.Pant
  • 2. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Outline § Introduction § Reservoir Properties ú Porosity ú Permeability ú Capillary Pressures ú Wettability ú Relative Permeability ú Reservoir Pressure § Basic PVT data § Reservoir fluid type § Drive Mechanism § Numerical simulation Mar-2009
  • 3. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Is the Party over ??“I should stress that we are not facinga re-run of the Oil Shocks of the1970s. They were like the tremorsbefore an earthquake. We now facethe earthquake itself. This shock isvery different. It is driven by resourceconstraints, …” (Dr Colin. J. Campbell) Mar-2010
  • 4. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. The law of Diminishing return 50 Hyperbolic Creaming Curve-North sea 45 40Cum Discovery, Gb 35 30 25 20 15 10 Actual Hyperbolic Model 5 0 0 500 1000 1500 2000 2500 3000 3500 Cum Wildcat wells Mar-2010
  • 5. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.The Hydrocarbon…. § Hydrocarbons are the simplest of the organic compounds. As the name suggests, hydrocarbons are made from hydrogen and carbon. The basic building block is one carbon with two hydrogens attached, except at the ends where three hydrogens are attached. Mar-2010
  • 6. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.The Hydrocarbons… § When the chain is between 5 and 9 carbons, the hydrocarbon is gasoline. § About a dozen carbons and it is diesel. § Around 20 carbons is motor oil. § A chain of hundreds to thousands of carbon and hydrogens make plastic. This particular plastic is polyethylene. Mar-2010
  • 7. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Definition-Reservoir Engineering§ “Application of scientific principles to the drainage problems arising during the development and production of oil and gas reservoirs”§ “The art of developing and producing oil and gas fluids in such a manner as to obtain a high economic recovery.” Mar-2010
  • 8. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Broad FunctionsReservoir Simulation Therefore the Ultimate goal is….. •Hydrocarbon in place •Recoverable hydrocarbons reserves •Rate of exploitation Mar-2010
  • 9. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Data Type§ Data that pertains to the reservoir rock and its extent ú Geologic & seismic data ú Well Log data ú Well test data ú Core data§ Data that pertains to the properties of reservoir fluids ú Composition of HC ú PVT Mar-2010
  • 10. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.The Traps Mar-2010
  • 11. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. PorosityPorosity of rock is the ratio of pore volume to bulk volume and is usually expressed as percentage Vp is pore volume Interconnected Vb is bulbk volume pores Vg is grain volume Isolated poresTotal or Absolute Porosity:ú It is the ratio of the volume of all the pores to the bulk volume of the material,Effective porosityú It is the ratio of the interconnected pore volume to the bulk volume Mar-2010
  • 12. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.A Pore Elements of Pore Throat Size & freq distribution-uncorrelated, correlated Connectivity of pores and throat-No of pore throat connecting to pores Spatial arrangement-Arrangement of pores of different sizes w.r.t each other The texture of a rock consists of its grain or mineral crystal size, the arrangement of the grains or crystals, and the degree of uniformity of the grains or crystals. Mar-2010
  • 13. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.The role of Rock Texture… Soi=(1-Swi) high Soi=(1-Swi) low Mar-2010
  • 14. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Pore Network-Reconstructed using thin section IMAGE AnalysisPorosity intergranular- 0.23 Porosity intergranular- 0.37Porosity total- 0.28 Porosity total- 0.39Absolute Permeability- 426md Absolute Permeability- 5600md Mar-2010
  • 15. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Saturation§ Saturation of a phase is the fraction of the pore volume occupied by the phase So+Sg+Sw=1 Connate water saturation (Swc) Critical Oil Saturation (Soc) Critical gas Saturation (Sgc)
  • 16. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Permeability§ Permeability is a measure of ‘ ease of flow’ or the capacity of formation to transmit fluids.§ Its unit is Darcy named after a French scientist Henry Darcy in 1856. ú Absolute Permeability: When only one fluid is present in the rock. It is a property of the rock and is independent of the fluid used in the measurement. This assumes that the fluid does not interact with the rock.(K) ú Effective Permeability: Effective permeability occurs when more than one fluid is present & is a function of the fluid saturation & the wetting characteristics of the rock. (Ko,Kw,Kg) Mar-2010
  • 17. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. PermeabilityThe permeability is measured byflowing a fluid of knownviscosity µ through a core plugof measured dimensions (A andL) and then measuring flow rateand pressure drop. Darcyequation becomes Mar-2010
  • 18. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Permeability Establishing a perfect Ø-K transform still remains a major challenge specially in ref to carbonates The carbonatesThe clastics Mar-2010
  • 19. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Improved Permeability estimation Phi Group - RQI Plot Porosity - Permeability Plot 10.000 1000.00 y = 8081.6x 2.5518 HU7, Core Permeability, mD 1.000 HU 7 100.00 HU 6 HU 5 HU6, y = 1648.1x2.3492 HU 4 y = 355.42x 2.0499 10.00 HU5, y = 245.68x 2.212RQI, micron HU 3 HU 2 HU4, 0.100 HU 1 1.00 y = 37.476x1.8785 HU3, y = 30.796x 2.1428 HU2, 0.10 0.010 y = 18.846x 2.4585 HU1, 0.01 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.001 0.010 0.100 1.000 Core Porosity Phi Group Mar-2010
  • 20. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Capillary pressure§ Combined effect of surface and IFT of the rock and fluid, pore size and geometry & wettability of the system. • Major effect of Cap pres is the creation of Transition Zone
  • 21. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Capillary pressure§ Drainage Process: ú Non Wetting phase displacing Wetting phase§ Imbibition Process: ú Wetting phase displacing Non wetting phase •Determination of Connate water •Establish Saturation –height relation •Rock Typing Mar-2010
  • 22. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Wettability§ ‘The tendency of a fluid to spread or adhere to a solid surface in presence of another immiscible fluid ‘ Mar-2010
  • 23. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Relative Permeability§ When two or more phases flow simultaneously the ratio of effective to absolute permeability is termed ‘Relative permeability’ Kro= ko/k Kre= kw/k Krg= kg/k Swc Soc NwP WP Mar-2010
  • 24. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Relative Permeability-Rock typing§ The variation in Rock Texture imparts significant changes in Rel perm estimates in core plugs of same formation Mar-2010
  • 25. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Relative Permeability-Core Condition§ Comparison of Rel- § Relative Permeability perms of cores with natural reservoir wettability preserved against a plug cleaned, dried and resaturated. Mar-2010
  • 26. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Relative Permeability-wettabilityType No Nw KrwWater 2-3 4-6 0.1-0.4WetMixed 3-5 2-4 0.5-0.9WetOil Wet 6-8 1.5-3 0.8-1.0 Mar-2010
  • 27. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Reservoir Pressure§ Reservoir Pressure§ The fluids confined in the pores of the reservoir rock occur under certain degree of pressure, generally called reservoir pressure ú The maximum pressure is called the static bottom hole pressure, the shut in pressure or static formation pressure Mar-2010
  • 28. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Well testing§ The response of the reservoir to change in production/ injection rates in a well is monitored§ The reservoir response is measured in terms of ‘pressure’ response & is usually dependent on K, Skin, Well bore storage, boundaries, fractures, dual porosity et.c ú Evaluation: Deliverability, Properties, Size ú Management: Refining forecast, Front movement ú Description: Faults, barriers P Res K,s,C Tqo P t Model K,s,C
  • 29. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Radial Flow in a porous media :For a single phase fluid flow (radial) in a constantpermeability and porosity for a fluid of small andconstant compressibility, the eauation is :Pws= Pi-162.6qµB/kh*log((T+∆t)/ ∆t)K= 162.6qµB mhS= 1.151[ P1hr-Pwf] –log (K / uCtrw2 )+3.23] m Mar-2010
  • 30. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Pressure Build-up analysis § Log-log Plot(Diagnostic plot): Log t Vs Log P § Horner Plot or MDH Plot : Horner Plot Log [(tp+ t)/ t] Vs Pwf Pskin= 0.87mSJactual = q . P*- PwfJideal = q . P*-Pwf- PskinFlow Efficiency = Jactual/ JidealD(distance of fault)=(0.00105K t/ uCt)1/2Where t = point at the time of intersection between two straight lines
  • 31. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Field Example XYZ 2222-2250.5m (B2) 3 distinct slopes K:588md, kh:17105 mdft Nearest distance to heterogeneity: 130ft Mar-2010
  • 32. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Field Example XYZ 2222-2250.5m (B2) 3 distinct slopes K:588md, kh:17105 mdft Nearest distance to heterogeneity: 130ft Mar-2010
  • 33. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. More data More Refinement Fig-4 L-II RFT Pressure Data 920 1983-84 940 1993-94 1997-98 960tvds s (m ) 980 1000 1020 1040 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 Normalised pressures ( psi) Mar-2010
  • 34. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Differing Aquifer Support I4 P3 I5 MDT pressure of layer-II I4 MDT pressure of layer-IV well P3-2/06 P2 well P3-2/06 I2 I5 well I5-9/062150 well P2-3/06 2260 well I2-10/06 well P4-4/06 well I5-9/06 well I1-06/082160 well I2-10/06 2270 Well I6-07/08 31% well I1-06/08 D1-14-10/07 Well I6-07/082170 D1-14-10/07 2280 Well P5-9/08 wELL p5-9/08 well p6 11/08 well p6-11/082180 2290 well p1-12/08 15%2190 23002200 23102210 23202220 23302230 23402240 23502250 2360 3160 3180 3200 3220 3240 3260 3280 3300 3320 3340 3360 3380 3400 3420 3440 3460 3480 3500 3520 3540 3560 2920 2940 2960 2980 3000 3020 3040 3060 3080 3100 3120 3140 3160 3180 3200 3220 3240 3260 3280 3300 3320 3340 3360 3380 3400 3420 3440 Mar-2010
  • 35. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Data - Fluid Properties§ Expressing HC in place in surface conditions§ Estimation of Pb,FVF,Rs,Bg, Viscosity§ Laboratory or empirical relations Mar-2010
  • 36. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Basic PVT Properties Mar-2010Mar-2010
  • 37. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Reservoir Fluid TypesTr<Tc Tc<Tr<Tct Tr>Tct§Black oil §Retrograde §Wet gas§Low shrinkage oil condensate §Dry gas§Volatile oil §Near Critical Cond gasMole Comp. Black Oil Volatile Oil Gas. Cond Dry gasC1 48.83 64.36 87.07 95.85C2 2.75 7.52 4.39 2.67C3 1.93 4.74 2.29 0.34C4 1.6 4.12 1.74 0.52C5 1.15 2.97 0.83 0.08C6 1.59 1.38 0.60 0.12C7+ 42.15 14.91 3.80 0.42 Mar-2010
  • 38. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.The Role of Heavy Components…. After Mccain,W.D
  • 39. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Phase Envelop-Black Oil Bo v/rv 1.2-1.3 GOR-v/v 35-125 API° 15-40 Colour Brown-GOR D.Green API Mar-2010 T T
  • 40. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Phase Envelop-Low shrinkage Oil Bo v/rv <1.2 GOR-v/v 35 API° <35 Colour Black Mar-2010
  • 41. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Phase Envelop-Volatile Oil Bo v/rv < 2.0 GOR-v/v 350-550 API° 45-55 Colour Greenish- Orange Mar-2010GOR API
  • 42. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Phase Envelop-Near Critical Crude Bo v/rv > 2.0 GOR-v/v > 550 API° 45-55 Colour Light Mar-2010
  • 43. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Phase Envelop-Retrograde GasCondensate GOR-v/v 1400-16000 API° > 50 Colour Light Mar-2010GOR API
  • 44. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Phase Envelop-Wet Gas GOR-v/v 11000- 18000 API° 60 Colour Light Mar-2010GOR API
  • 45. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Phase Envelop- Dry Gas GOR-v/v >18000 API° > Colour Light Mar-2010
  • 46. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Drive mechanism§ Depletion drive: Expansion of gas evolved from solution ú No free gas cap and no active water drive ú Rapid pressure decline ú Water free production ú Rapidly increasing GOR ú Low ultimate oil recovery (5-20%) Mar-2010
  • 47. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Drive mechanism§ Gas Cap drive: Expansion of Gas cap gas ú Gas cap and no or small active water drive ú Less rapid pressure decline ú Water free production ú Rapidly increasing GOR in structurally high wells ú Moderate ultimate oil recovery (25-40%) Mar-2010
  • 48. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Drive mechanism§ Water Drive: Production of oil by water displacing process is & usually most efficient process ú Very gradual pressure decline ú Little change in producing GOR ú Early water production from structurally lower wells ú High ultimate recovery Mar-2010
  • 49. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Drive mechanism§ Gravity Drainage: As a result of difference in reservoir fluid densities ú Low GOR in structurally low wells ú Formation of Secondary GCG ú High GOR in structurally high wells ú Little or no water production ú High ultimate recovery ú Variable rate of pressure decline Mar-2010
  • 50. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Asphaltene –The problem Mar-2010
  • 51. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Scales for reservoir heterogeneity MICRO Thin sections MACRO CoreMEGAWell loggingWell test3D seismic GIGA Seismic Basin studies RSIN3 Mar-2010
  • 52. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Reservoir simulation§ The dictionary meaning of the word ‘simulate’ is ‘to give an appearance of’§ Forms an integral part of Reservoir Management Functions (RMF) Mar-2010
  • 53. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Reservoir simulation§ Mimics the behavior of a real system through a model (physical, analog, electrical or numerical) based on realistic assumptions§ Simulation can be close to reality but it is never the reality ( should approach reality with time) Mar-2010
  • 54. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Disciplinary contributions to reservoir modeling Seismic Fluid Interpretation Petrophysics Properties NUMERICAL Geological SIMULATION Surface Model MODEL Facilities Wells Model Grid Vertical Economics Effects Horizontal Multilateral RSIN1 Mar-2010
  • 55. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Numerical Model§ Mathematical models System of equations describing the physical behavior These are complicated nonlinear partial differential equations relating pressure and saturation changes with time Analytical solutions-generally impossible Numerical solutions –generally the only way Mar-2010
  • 56. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Numerical Models§ Basic equations for fluid flow ú Conservation of mass ú Conservation of momentum ú Conservation of energy ú Rate Equation ú EOS Mar-2010
  • 57. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Numerical Models§ Numerical solution produces answer at discrete points within the system§ Use of ‘finite difference’ for transforming the continuous differential equation to discrete form-both space and time are discretized (grid, timesteps)§ Common solution procedures • IMPES, Newton-Raphson Mar-2010
  • 58. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Stochastic Modeling § Measures statistical variation in data points-maps similar statistical properties § Better describes the heterogeneity of the reservoir- (variograms-trends, direction) § Integrates independent measurements § Uncertainty in measured values-assessed § Algorithm-Kriging, Conditional simulation,co-krigingMar-2010
  • 59. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only. Scales for reservoir heterogeneity MICRO Thin sections MACRO Grouping of fine layers for upscaling Core 1 2 3 4 100% 80% 60% 40% 20% 0% 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 Fine layers of a parasequence <1 1 to 10 10 to 100 >100MEGAWell loggingWell test RSIN33D seismic GIGA Seismic Basin studies Mar-2010
  • 60. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.History Match-First Realization Mar-2010
  • 61. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.History Match -Final Realization Mar-2010
  • 62. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Layer-9(c)
  • 63. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Parallel Simulation 10 million cell 1 billion cell
  • 64. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Role & Impact ú Corporate impact-cash flow predictions ú Insight to the various physical process ú Sensitivity ú Comparing different exploitation scenarios ú Optimize project design to maximize economic recovery ú Real Time monitoring Mar-2010
  • 65. Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.Thanks for patient hearing Mar-2010