Simulation of Polymer Gel Injection Well Treatments

1. Simulation of Polymer Gel Injection Well Treatments Chuck Norman Tiorco, Inc. Tiorco de Argentina

2. Agenda • Flood-Out Waterflood Model • Input • Model Process • Information Generated by the Waterflood Model • Flood-Out Polymer Gel model • Dykstra-Parsons Theory • Information generated by the Gel Model • Forecasts with the Gel Model (Examples)

4. ABILITY TO CONTROL LAYER PROPERTIES ACCORDING TO IN-SITU CHEMICAL CONCENTRATIONS: • RESERVOIR (TOTAL) • ADSORBED (IMMOBILE) • MOBILE (PRODUCIBLE)

5. MANDATORY – PVT & reservoir data What data entry is required?

6. MANDATORY – model layers What data entry is required? NOTE: MORE LAYERS RESULT IN IMPROVED FORECASTING RESOLUTION AS EACH LAYER CONTRIBUTES ONE “POINT” IN THE TYPE-CURVE

7. MANDATORY – production profiles What data entry is required?

8. OPTIONAL – log layers What data entry is required?

9. The flood-out Process 01 Import fine resolution log data and define coarse model layers - 02 Create coarse model layers -

10. The flood-out Process 03 Generate forward model pseudo-relative permeability - 04 Generate forward model fractional flow -

11. The flood-out Process 05 Generate the forward model production type-curve - 06 View the first-pass water-cut history match (match needs improvement) - First-pass: Poor history match!

12. The flood-out Process 07 Generate reverse model fractional flow - 08 Generate reverse model pseudo-relative permeability -

13. The flood-out Process 09 Generate the reverse model “Eglew” layers - < New Versus Old > < New Versus Old >

14. The flood-out Process 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 -

15. The flood-out Process 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 -

16. The flood-out Process 15 Create a flood-out slide show and generate synthetic logs - 16 forecast production and injection by multi-cell material balance -

17. Dykstra-Parsons’ Water Flood Theory adapted to Chemical Flood Modeling 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

18. Polymer Flood Model: How does it work? Dykstra-Parsons’ theory is employed to accomplish the following (at each time step) for a user-specified set of Model Layers: Determine relative flood-frontal advancement for each layer Generate a type-curve (Oil Recovery Factor versus Water-cut), which is interpolated by the forecasting optimiser Once polymer is introduced, layer permeability is altered according to resistance factor expressed as a function of in-situ (i.e. reservoir) polymer concentration (ppm) Highly-permeable layers accept larger water injection volumes, and consequently polymer concentration builds-up preferentially in these layers. This stabilises the flood, or invokes profile conformance.

19. Dykstra-Parsons’ Water Flood Theory adapted to Chemical Flood Modelling A spreadsheet employing non-linear regression automatically finds a cubic polynomial of best-fit to tabulated data RESISTANCE FACTOR HOW DOES IT WORK? High K Layers build-up the highest polymer concentration, which alters layer flow-velocity order and invokes profile conformance. Note: THIS CURVE APPLIES FOR A FIXED INJECTION RATE IN-SITU POLYMER CONCENTRAION

20. Polymer Gel Model Output and Forecasts

21. Re-commence “pure” water injection In this example, polymer is injected over a three month period: Month1 – 500 ppm Month2 – 1000 ppm Month3 – 1500 ppm produced polymer concentration in-situ or reservoir polymer concentration adsorbed polymer concentration

22. Produced polymer concentration – high permeability layers are produced preferentially Zoomed view of “production side” in-situ or reservoir polymer concentration adsorbed polymer concentration NOTE that the adsorbed polymer concentration dilutes once “pure” water injection re-commences Polymer injection “flag”

23. Production response to the polymer flood Actual Water Injection Rate (AWIR) is optional User input Produced water rate decreases due to polymer injection Oil rate increases due to polymer injection

24. Re-commence “pure” water injection Resistance Factor > Once polymer injection ceases, displaced by “pure” water injection, the resistance factor decreases. Adsorbed polymer is entrapped in order to model residual resistance.

25. Average Permeability changes with in-situ polymer concentration Re-commence “pure” water injection

26. Maximum permeability of all model layers NOTE: standard deviation of K is a measure of profile conformance, enhanced by the injection of polymer (i.e. Std Dev. decreases once polymer is introduced) Average permeability and standard deviation of model layer permeability

27. Mobility Ratio “M” decreases as the flood front stabilises Commence polymer injection Mobility Ratio “M” increases as the in-situ polymer concentration dilutes (i.e. post-polymer flood)

28. WOR: water flood (base case – left) versus polymer flood (right) Reduced WOR due to polymer injection Base Case Water-flood “BEFORE” AND “AFTER” PRODUCTION PERFORMANCE -

29. Oil Rate: water flood (base case – left) versus polymer flood (right) Oil rate uplift due to polymer injection Base Case Water-flood “BEFORE” AND “AFTER” PRODUCTION PERFORMANCE -

30. 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

31. 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 Polymer injection “flag” adsorbed polymer concentration

32. Layer # 20 Oil Rate increases as the model allocates more Water Injection to layer # 20 (i.e. following the commencement of polymer injection) Water breakthrough at producer for layer # 20 Layer # 20 100% flooded

33. Re-commence “pure” water injection Layer # 20 Resistance Factor > Once polymer injection ceases, displaced by “pure” water injection, the resistance factor decreases. Adsorbed polymer is entrapped in order to model residual resistance.

34. Layer # 20 Permeability changes with in-situ polymer concentration Re-commence “pure” water injection

35. Simulation of Polymer Gel Injection Well Treatments Chuck Norman Tiorco, Inc. Tiorco de Argentina