1. Texas A&M UniversityFeb, 2004 Application of X-Ray CT to Investigate Effect of Rock Heterogeneity and Injection Rates During CO 2 Flood Process Deepak Chakravarthy Master’s Division

2. Texas A&M UniversityFeb, 2004 Topics of Discussion  Introduction  Problem Outline  Objective  Experiment Outline  Results  Conclusions

3. Texas A&M UniversityFeb, 2004 Topics of Discussion  Introduction  Problem Outline  Objective  Experiment Outline  Results  Conclusions

4. Texas A&M UniversityFeb, 2004 Introduction  Enhanced Oil Recovery  CO 2 flooding – One of the most widely used! Why ?

5. Texas A&M UniversityFeb, 2004 Introduction  Lithology -- Works well in:  Sandstone (55% of current floods)  Carbonates (35% of current floods)  Others (about 10%)  Secondary or Tertiary  Oil saturation from <20% to 85% at start of flood  Average S o for current flood is 55%  Water cuts as high as 98% at start Broad Applicability

6. Texas A&M UniversityFeb, 2004 Introduction  Miscible flood  Extraction of light to intermediate hydrocarbons  Oil swelling  Viscosity reduction Mechanisms

7. Texas A&M UniversityFeb, 2004 Introduction  Miscible flood  Extraction of light to intermediate hydrocarbons  Oil swelling  Viscosity reduction Problems ?

8. Texas A&M UniversityFeb, 2004 Problem Outline  Reservoir heterogeneity  Low viscosity and high mobility  Natural fractures Limiting Factors

9. Texas A&M UniversityFeb, 2004 Objective Investigate mechanisms of oil bypass during CO 2 flooding X-Ray CT Scanner

10. Texas A&M UniversityFeb, 2004 Topics of Discussion  Introduction  Problem Outline  Objective  Experiment Outline  Results  Conclusions

11. Texas A&M UniversityFeb, 2004 Experiment Outline Workstation3D CT Image Digital Detector X-Ray Source Object X-Ray Tomography

12. Texas A&M UniversityFeb, 2004 Experiment Outline  CT number  Depends on density  Every material has a characteristic CT number  E.g. CT for air = -1000 X-Ray CT Basics

13. Texas A&M UniversityFeb, 2004 CT Scanner

14. Texas A&M UniversityFeb, 2004 Experiment Outline Prepare Core Scan Dry Core CO 2 Saturated Core Scans Dope Oil Saturate in Vacuum Chamber Experiment Procedure

15. Texas A&M UniversityFeb, 2004 Experiment Outline

16. Texas A&M UniversityFeb, 2004 Experiment Outline  Displaced Fluid - Soltrol TM Refined Oil  Displacing Fluid - CO 2  Pressure - 800 psig  Temperature - 75° F  CO 2 phase - Vapor Experiment Summary

17. Texas A&M UniversityFeb, 2004  Highest Injection Rate - 0.09 cc/min Experiment Outline Experiment Summary

18. Texas A&M UniversityFeb, 2004  Highest Injection Rate - 0.09 cc/min  Lowest Injection Rate - 0.03 cc/min Experiment Outline Experiment Summary

19. Texas A&M UniversityFeb, 2004  Highest Injection Rate - 0.09 cc/min  Lowest Injection Rate - 0.03 cc/min  Lowest rate with heterogeneous (fractured) core - 0.03 cc/min Experiment Outline Experiment Summary

20. Texas A&M UniversityFeb, 2004 Topics of Discussion  Introduction  Problem Outline  Objective  Experiment Outline  Results  Conclusions

21. Results Dry core scans with bright blue regions indicating higher CT numbers - i.e. higher density

22. Results Oil saturated core scans with red color indicating higher CT numbers

23. Results CO 2 Injection at 15 minutes shows CO 2 as a blue spot at the center

24. Results CT Scans at 25 minutes after start of injection

25. Results CT Scans at 35 minutes after start of injection

26. Results CT Scans at 60 minutes after CO2 injection

27. Results CT Scans at 120 minutes after CO2 injection

28. Results Sample plots showing decrease in CT number with increase in CO 2 Saturation

29. Results Porosity equation Saturation equation

30. Results CO 2 Saturation – 15 MinutesCO 2 Saturation – 25 Minutes CO 2 Saturation – 35 MinutesCO 2 Saturation – 60 Minutes

31. Injection rate = 0.09 cc/min Oil Saturated Core CO 2 Injection – 15 Minutes 25 Minutes 30 Minutes 60 Minutes 120 Minutes

32. 100% Oil Saturated 30 Minutes 60 Minutes 120 Minutes 150 Minutes 180 Minutes 300 Minutes Injection rate = 0.03 cc/min

33. Texas A&M UniversityFeb, 2004 Injection Rate = 0.09 cc/min Results

34. Texas A&M UniversityFeb, 2004 Results Injection Rate = 0.03 cc/min

35. Fractured Core – 100% Oil Saturated Results

36. CO 2 flowing through fracture Results

37. CO 2 flow is confirmed by lower CT number at the fracture Results

38. Reconstructions indicating CO 2 flow through fracture Results

39. Texas A&M UniversityFeb, 2004 Topics of Discussion  Introduction  Problem Outline  Objective  Experiment Outline  Results  Conclusions

40. Texas A&M UniversityFeb, 2004 Conclusions  Heterogeneity and injection rates play an important role in affecting oil recovery and breakthrough.

41. Texas A&M UniversityFeb, 2004 Conclusions  Heterogeneity and injection rates play an important role in affecting oil recovery and breakthrough.  Early breakthrough and higher oil bypass are observed at high injection rates.

42. Texas A&M UniversityFeb, 2004 Conclusions  Heterogeneity and injection rates play an important role in affecting oil recovery and breakthrough.  Early breakthrough and higher oil bypass are observed at high injection rates.  Low injection rate gives better sweep and lesser utilization of CO 2.

43. Texas A&M UniversityFeb, 2004 Conclusions  Injection rates must be optimized before the start of injection.

44. Texas A&M UniversityFeb, 2004 Conclusions  Injection rates must be optimized before the start of injection.  In a fractured system, fluid flow occurs mainly through the fractures.

45. Texas A&M UniversityFeb, 2004 Conclusions  Injection rates must be optimized before the start of injection.  In a fractured system, fluid flow occurs mainly through the fractures.  Considerable amount of time is required for the injection fluid to penetrate the matrix.

46. Texas A&M UniversityFeb, 2004 Conclusions  An alternative method like WAG or Foam and conformance control (polymer) is necessary to increase sweep efficiency and mitigate the bypassing during CO2 injection in the fractured system.