1. Pioneer Natural Resources
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. CHALLENGES 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
Models
Archie
Simandaux
Dual water
Waxman-Smits
Indonesian

6. SPRABERRY MAKEUP- LOOKS COMPLICATED ??

7. 1U PAYZONE MINERALIZED FRACTURE

8. METHODOLGY DATA GATHERING DATA EDITING LITHOLOGY DETERMINATION
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 GM/CC
LIMESTONE GM/CC
DOLOMITE GM/CC

11. True matrix density can be determined
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

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. Hey!!! That’s a fractured formation—Why?? m = 1.2
(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
Effective 
Density 

28. Non productive Zones
P 1/2 mean
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