Surfactant-Based Enhanced Oil recovery Processes and Foam Mobility Control Task 4: Simulation of Field-Scale Processes

1. Surfactant-Based Enhanced Oil recovery Processes and Foam Mobility ControlTask 4: Simulation of Field-Scale Processes Mojdeh Delshad Gary Pope Glen Anderson Hourshad Mohammadi Nariman Fathi Center for Petroleum and Geosystems Engineering The University of Texas at Austin Austin, Texas • June 4, 2005

2. Objectives • Design and optimize a surfactant flood for Midland Farm oil reservoir • Study the effect of wettability on the performance of surfactant flood • Literature survey on effect of wettability on petrophysical properties • Develop and implement a procedure to model wettability alteration

3. Base Case Midland Farms Simulation • Matching Water Injection Rate • Permeability Field • Relative Permeability Curves • Waterflood Injection Rate • Design Parameters • Base Case Results • Production Rates • Cumulative Oil Recovery • Production History • Oil Saturation Profiles • Surfactant Concentration Profiles • Residual Oil Saturation Profiles • Sensitivity Analysis

4. Permeability Field Stochastic Permeability Field Vdp=0.75 lx = ly = 20 ft lz = 4 ft

5. Relative Permeability Curves Corey Type Parameters

6. Water Injection Rate and Phase Cut during Waterflood

7. Design Parameters

10. Chemical Flood Production Rates (1 PV Polymer Drive)

11. Chemical Flood Oil Recovery(1 PV Polymer Drive)

12. Produced Phase Cuts during Chemical Flood(1 PV Polymer Drive)

13. Produced Chemical Concentrations(1 PV Polymer Drive)

14. Oil Saturation During Chemical Flooding 0.2 PV 0.75 PV 1.25 PV

15. Surfactant Concentration 0.2 PV 0.75 PV 1.25 PV

16. LxWxH 660x660x30 ft Grid Blocks 11x11x5 Depth to Pay 4700 ft Initial Pressure 1975 psi Reservoir Temperature 103 oF Average Permeability 80 md Porosity 0.16 Water Compressibility 3x10-6 psi-1 Oil Compressibility 1x10-5 psi-1 Water Density 62.43 lb/ft3 Oil Density 54.33 lb/ft3 Water Viscosity 0.7 cp Oil Viscosity 5 cp Water/Oil IFT 20 dynes/cm Constant Injection Rate 250 bbl/day Constant Production Pressure 300 psi Reservoir and Fluid Properties

17. Effect of Wettability on Sor

18. CDC for Berea Sandstone (Amaefule 1982)

19. CDC in Berea Sandstone (Mohanty 1983)

20. CDC in Carbonates (Kamath 2001)

21. Permeability Distribution md

22. Effect of Wettability on Relative Permeability

23. Effect of Wettability on Capillary Pressure

24. Effect of Wettability on Waterflood Recovery

25. Effect of Wettability on Chemical Oil Recovery

26. Effect of Wettability on Reservoir Pressure

27. Effect of Wettability on Oil Production Rate

28. Oil Saturation during Waterflood (Waterwet Case) 0.2 PV 0.9 PV

29. Oil Saturation during Waterflood (Mixedwet Case) 1.0 PV 3.5 PV

30. Oil Saturation during Waterflood (Oilwet Case) 0.3 PV 1.9 PV

31. Oil Saturation during Surfactant Flood (Waterwet Case) 0.25 PV 2.25 PV 0.75 PV

32. Oil Saturation during Surfactant Flood (Mixedwet Case) 0.25 PV 2.25 PV 0.75 PV

33. Oil Saturation during Surfactant Flood (Oilwet Case) 0.25 PV 2.25 PV 0.75 PV

34. Surfactant concentration at 0.75 PV Waterwet Mixedwet Oilwet

35. Final Oil Saturation Mixedwet Waterwet Oilwet

36. Wettability Alteration • Wettability Index vs. surfactant properties • Residual saturation • Relative Permeability • Capillary pressure • Capillary desaturation

37. Model 1: Wettability Effect Only • Read the table of water and relative permeabilities vs. water saturation for the in-situ wettability i.e mixed-wet • Read the table of water-oil capillary pressure vs. water saturation for the in-situ wettability • Read another set of tables for the altered wettability i.e water-wet • Check the gridblock value of surfactant concentration at each time step • Switch the tables if the surfactant concentration is above an input tolerance

38. Model 2: Effect of Wettability and Mobilization • Relative permeability curves for oil and water at two extreme wettability conditions • Capillary pressure curves for two extreme strongly water-wet and strongly oil-wet • Capillary desaturation curves for each phase at the two extreme conditions of wettability

39. Strongly water-Wet Relative permeability at low IFT Capillary desaturation curves Relative permeability at high IFT Strongly Oil-Wet Relative permeability at low IFT Capillary desaturation curves Relative permeability at high IFT Model 2 - Linear Interpolation

40. Relative Permeability Curves (Morrow 1973)

41. High NC Relative Permeability • Calculate relative permeability endpoints • Calculate relative permeability exponent

42. Model 2 - Linear Interpolation F = constant Or Or Develop new relationship based on lab. data

43. Model 3: Under Development! • Determine the Wettability Index in each gridblock and each time step based on surfactant property • Compute residual saturations as a function of Wettability Index

44. Sor vs Wettability Correlation

45. Sor vs. Wettability Index for Berea Core

46. Normalized Residual Oil Saturation vs. Wettability Index (All Data)

47. Wettability and CDC Indiana Limestone (Abrams) Capillary Number Berea Sandstone (Gupta)

48. Trapping Number vs Wettability Index Correlation

49. Computation Procedure • Establish relative permeability, capillary pressure, and capillary desaturation curves for initial and altered wettability conditions • Determine the change in Wettability Index (IW) in the presence of surfactant • Develop a correlation between residual saturation and IW • Develop a correlation between trapping number and IW • Compute high capillary number relative permeability for altered wettability