TRANSCENDING CONVENTIONAL LOG INTERPRETATION- A MORE EFFECTIVE APPROACH FOR SPRABERRY RESERVOIR

1. TRANSCENDING CONVENTIONAL LOG INTERPRETATION- A MORE EFFECTIVE APPROACH FOR SPRABERRY RESERVOIR Pioneer Natural Resources DICMAN ALFRED M.S Texas A&M University

2. LOCATION

3. HIGH’S AND LOW’S • At least 15% of all oil remaining in class 3 (slope-basin and clastic basin) reservoirs may be in the Spraberry trend • Estimated 6 billion bbl oil remain in Spraberry reservoirs • Waterflooding was initiated in 1950’s without much success • Current ultimate recovery is no greater than 10% of original oil in place • Presence of fractures has a dominating influence on performance

4. OBJECTIVES • To analyze logs effectively and determine average water saturation • To establish pay zones and cut-offs • To recommend a suitable logging program

5. Absence of clean water bearing zones Fractured Nature of the Formation Lack of Rw value to establish water saturations using the models available in the industry CHALLENGES Models Archie Simandaux Dual water Waxman-Smits Indonesian

6. SPRABERRY MAKEUP- LOOKS COMPLICATED ??

7. 1U PAYZONE MINERALIZED FRACTURE

8. METHODOLGY DATA GATHERING DATA EDITING CORE ANALYSIS LITHOLOGY DETERMINATION SOFTWARE PRIZM® DETERMINATION OF POROSITY EXPONENT m

9. P ½ CALCULATION AND PLOT DETERMINATION OF P ½ MEAN DETERMINATION OF WATER SATURATION RECOMMEND LOGGING PROGRAM

10. Why is matrix density is so vital for the analysis of fractured zones ?? Density porosity is given by By convention SANDSTONE 2.65 GM/CC LIMESTONE 2.71 GM/CC DOLOMITE 2.87 GM/CC

11. INGREDIENTS FOR SUCCESS True matrix density can be determined • From core analysis • From complex mineral lithology plots (using software packages) • By interplay between Hingle and Pickett plot (which also gives the cementation component “m”)

12. Determination of matrix density from core Matrix density

13. 4 MINERAL PLOT USING PRIZM® Shale streak marker

14. LITHOLOGY 1U WELL#37 The points fall in the sandstone region

15. HINGLE AND PICKETT INTERPLAY Assume “m” Find ρma Hingle Pickett m Log(ρma-ρb) (1/R t) (1/m) ρma ρb Log(R t) Estimate “m” Estimate “m” Hingle Pickett Find ρma (1/R t) (1/m) m Log(ρma-ρb) ρma ρb Log(R t)

17. (m-b) ,GM/CC Rt, OHMM Hey!!! That’s a fractured formation—Why?? m = 1.2

18. COMPARISON IN WELL # 39 5U Sonic  Core  Core  Effective  Density  Density 

19. AVERAGE WATER SATURATION • Calculated using a statistical parameter P ½, originally introduced by Porter, Pickett and Whitman. • Empirically, P ½ has a normal distribution for intervals which are filled with water. • Intervals with some hydrocarbon saturation deviate from the normal distribution. The parameter is defined by If Sonic Log is used,

20. Hydrocarbon zones Non-productive zones

21. P ½ mean

22. Hydrocarbon zones Non-productive zones

23. DETERMINATION OFAVERAGE WATER SATURATION Resistivity Index Conventional Water saturation is given by

24. WELL # 39 1U Sw BVW OIL

25. 5U

26. Comparison of Core vs Porosity 1U Well#37 Core  Core  Effective  Density 

28. Non productive Zones P 1/2mean Cummulative frequency

29. 1U Density caliper lost contact 5U

30. WELL #37 Sw 1U BVW OIL

31. 5U

33. CONCLUSIONS • The Density log derived porosity is found to approximately correlate with core porosity after suitable corrections. • The water saturation derived from statistical parameter P ½ gives acceptable values compared to the other models used in the industry . Sonic log gave better results than density log. • This method can be employed in formations whose Rw is difficult to obtain. • The payzones and cutoffs can be established from the saturation values

34. RECOMMENDATIONS An ideal Logging Suite for the Spraberry Trend will be Spectral Gamma log Density log Sonic log Induction log