Flood Forecasting using Classical Reservoir Engineering Techniques

1. Flood Forecasting using Classical Reservoir Engineering Techniques • By Graeme Morrison (M.Eng. – P.Eng., MSPE) • Flood-Out (UK) Ltd • grm@flood-out.co.uk

2. Flood Forecasting using ClassicalReservoir Engineering Techniques A credible forecast needs to be linked to a reservoir model • There are COMMERCIAL, OPERATIONAL DRIVERS to forecast accurately. For example, forecast to plan and scope well interventions such as water shut-offs and scale squeezes. • Forecasting is more than a financial planning tool. Reservoir Model Production Performance physics LINK Geology & Oil In-Place Volume ? WOR > maths

3. Flood Forecasting using ClassicalReservoir Engineering Techniques A credible forecast needs to be linked to a reservoir model • Classical techniques establish the important LINK • They do it: efficiently, cost-effectively, rigorously Reservoir Model Production Performance physics LINK Geology & Oil In-Place Volume ? WOR > maths

4. Flood Forecasting using ClassicalReservoir Engineering Techniques CONTENTS: • introduction and aim • modelling process • model application • conclusions

5. Flood Forecasting using ClassicalReservoir Engineering Techniques • Stiles (generate pseudo-relative permeability) • Buckley-Leverett / Welge (forecasting water-cut and rate) • Dykstra-Parsons (forecasting water-cut, rate & reservoir visualisation) • Multi-cell Material Balance (forecasting pressure for a given rate) APPLIED TO: - Water Flood - Chemical Flood (EOR) When these techniques are integrated: THE WHOLE IS GREATER THAN THE SUM OF THE PARTS

6. Flood Forecasting using Classical Reservoir Engineering Techniques

7. Flood Forecasting using ClassicalReservoir Engineering Techniques SO WHY WOULD YOU USE THESE CLASSICAL TECHNIQUES ?

8. Flood Forecasting using ClassicalReservoir Engineering Techniques OPTIMAL CONDITIONS UNDER WHICH CLASSICAL TECHNIQUES APPLY: • Steady-State flood conditions – reservoir voidage is maintained & pressure remains above the bubble point • Diffuse flow (Sw uniformly distributed vertically) – requires: (a) Pc & Gravity small relative to Injection / Offtake Rate; or, (b) low injection rates and Pc huge! (VE applies) • Stiles assumes Mobility Ratio (M) is approximately unity (1) • DYKSTRA-PARSONS’ THEORY: (a) is applicable for all mobility ratios (b) assumes layers flood-out in flow-velocity order (c) layer cross-flow does not occur

9. Dykstra-Parsons’ Theory Refer to – “The Practice of Reservoir Engineering” – by L. P. Dake (1994) Elsevier

10. Dykstra-Parsons’ example Time Increases > Water-Cut Increases > SYNTHETIC LOGS: - PLT / RST are rarely run for the purposes of reservoir management these days - Dykstra-Parsons may be utilised to generate synthetic logs at a specified day - Accuracy of synthetic logs requires tuning the model to data base of log responses

11. Quantify Water Shut-off Uplift WATER SHUT-OFF UPLIFT: 150 Mstb accelerated at 5% discount rate At £5 / bbl net back > NPV = £750,000 less costs Oil Rate increased by 1,000 stbopd Water-Cut reduced by 10%

12. A Water Flood Modelling Process

13. An Example of the Process in Action 01 Import fine resolution log data and define coarse model layers - 02 Create coarse model layers -

14. An Example of the Process in Action 03 Generate forward model pseudo-relative permeability - 04 Generate forward model fractional flow -

15. An Example of the Process in Action 05 Generate the forward model production type-curve - First-pass: Poor history match! 06 View the first-pass water-cut history match (match needs improvement) - But don’t stop here ! Try the “reverse” model to improve the match>>

16. An Example of the Process in Action 07 Generate reverse model fractional flow - 08 Generate reverse model pseudo-relative permeability - But don’t stop the reverse process here ! De-convolute the pseudo-relative permeability to generate layer K and K’ro >>

17. An Example of the Process in Action 09 Generate the reverse model “Eglew” layers - < New Versus Old > < New Versus Old > NEW LAYER PROPERTIES OLD LAYER PROPERTIES

18. An Example of the Process in Action 10 Generate a new forward model pseudo-relative permeability - 11 Generate a new forward model fractional flow - 12 Generate a new forward model production type-curve -

19. An Example of the Process in Action 13 An improved water-cut history match results from importation of the reverse model into the forward model - 14 An optimised production and injection forecast can now be generated within system’s constraints -

20. An Example of the Process in Action 15 Create a flood-out slide show and generate synthetic logs - 16 forecast production and injection by multi-cell material balance -

21. The Hidden Potential ofClassical Reservoir Engineering Techniques < New Versus Old > < New Versus Old > NEW LAYER PROPERTIES OLD LAYER PROPERTIES

22. Flood Forecasting using ClassicalReservoir Engineering Techniques K after K before AUTOMATED PERMEABILITY TUNING TO ACHIEVE A WATER-CUT HISTORY-MATCH AUTO-TUNE SNOSRAP-ARTSKYD BROADER APPLICATION OF THIS TUNING PROCESS: DETERMINE LAYER PERMEABILITY FROM WATER-CUT !

23. The Hidden Potential ofClassical Reservoir Engineering Techniques Permeability from Water-Cut

24. The Hidden Potential ofClassical Reservoir Engineering Techniques K’ro end-point from Water-Cut (INSITU rather than via SCAL!)

25. Water Flood Reality CheckEstimation of OIIP for anassumed Recovery Factor Water-cut fw vs Sw OIIP too HIGH Fractional Flow (reverse model) fw vs Sw fw vs Sw Assumed OIIP feasible OIIP too LOW

26. The Practical Application ofClassical Reservoir Engineering Techniques 1-Jan-2005 well difficult to kick-off with gas-lift A Case Study WOR

27. The Practical Application ofClassical Reservoir Engineering Techniques Date: mid-2004 Date: end-2004

28. The Practical Application ofClassical Reservoir Engineering Techniques Multi-cell material balance Matched to actual BHP

29. The Practical Application ofClassical Reservoir Engineering Techniques Switch-on water injection Multi-cell material balance

30. The Practical Application ofClassical Reservoir Engineering Techniques Natural Depletion Case Switch-on water injection

31. The Chemical Flood (EOR) Application ofClassical Reservoir Engineering Techniques DYKSTRA-PARSONS’ THEORY IS ADAPTED TO MODEL: • Polymer Flood (predict improved profile conformance) • Mobility Control flood modelling (change viscosity ratio) • Alkaline-surfactant flood modelling (reduce Sor)

32. The Chemical Flood (EOR) Application ofClassical Reservoir Engineering Techniques

33. The Chemical Flood (EOR) Application ofClassical Reservoir Engineering Techniques

34. Dykstra-Parsons’ Water Flood Theory adapted to Chemical Flood Modelling The Polymer Flood Model allows the User to track the performance of any Model Layer – here and in the following slides layer # 20 performance is shown. Layer # 20 100% flooded Dykstra-Parsons relative layer water flood penetration distance (versus time) for layer # 20 Layer # 20

35. Dykstra-Parsons’ Water Flood Theory adapted to Chemical Flood Modelling Polymer production (at the producing well) only commences once the layer has 100% flooded (according to Dykstra-Parsons’ Theory) – prior to layer-by-layer water breakthrough each layer produces clean oil into the producing well. in-situ or reservoir polymer concentration Produced polymer concentration Layer # 20 Polymer injection “flag” adsorbed polymer concentration

36. Dykstra-Parsons’ Water Flood Theory adapted to Chemical Flood Modelling Layer # 20Oil Rateincreases as the model allocates moreWater Injectionto layer # 20 (i.e. following the commencement ofpolymer injection) Water breakthrough at producer for layer # 20 Layer # 20 100% flooded Layer # 20

37. Flood Forecasting using ClassicalReservoir Engineering Techniques CONCLUSIONS • Classical Techniques are powerful – 50 years on they offer a commercial advantage • These techniques remain relevant because the laws of physics don’t date • Useful in support of operational decision-making • Efficient and Inexpensive to implement • Complimentary to finite-difference simulation • EOR / chemical flood modelling capability

38. Flood Forecasting using ClassicalReservoir Engineering Techniques BACK-UP SLIDES

39. Flood Forecasting using ClassicalReservoir Engineering Techniques VE – VERTICAL EQUILBRIUM • A large vertical permeability (Kv) • Small reservoir thickness (H) • Large density difference between the fluids • High capillary forces (large transition zone) • Low fluid viscosities • Low injection rates (capillary-gravity equilibrium is established instantaneously relative to Darcy or viscous forces operating parallel to the reservoir bedding planes) • Fluid potential equilibrium across the thickness of the reservoir, i.e. hydrostatic equilibrium for which the saturation height can be determined in accordance with capillary-gravity equilibrium.

40. Dykstra-Parsons’ Water Flood Theory adapted to Chemical Flood Modelling RESISTANCE FACTOR: • Resistance Factor (ResFac) is an experimentally measured quantity expressing the relative degree of force required to move a liquid through a porous media. ResFacinj = λbase / λinj λinj = injected fluid mobility and λbase = baseline fluid mobility where λ = K’r . K / μ

41. BARRIERS TO SUCCESSFUL IN-SITU MODELLING OF CHEMICAL FLOOD PROCESSES >> Dykstra-Parsons’ Water Flood Theory adapted to Chemical Flood Modelling Macroscopic > layer scale model research Microscopic pore scale > Mechanistic (theoretical) Deterministic (experimental)