1. Selecting Seismic Attributes and Proper Display Parameters An abridged review of a study conducted on 3-D seismic over Sooner Field, CO By: William C. (Bill) Overman, MS Geophysicist

2. (303) 429-5425W.C. Overman, MS, Geophysicist2 Slide 2: Sooner Field overview Lower Cretaceous D-sand Stratagraphic component –valley fill sand body Structural influence critical to trap Significant IPP for the D-J Basin

3. (303) 429-5425W.C. Overman, MS, Geophysicist3 Slide 3: Amplitude Seismic Attribute Amplitude from the top of the D sand Strong energy from the sand body Strong energy everywhere else! Does not discriminate prospective vs. back ground

4. (303) 429-5425W.C. Overman, MS, Geophysicist4 Slide 4: Peak to Trough Attribute Anomaly only identifies south half of the sand body Does not present additional drilling opportunities!

5. (303) 429-5425W.C. Overman, MS, Geophysicist5 Slide 5: Instantaneous Frequency Crossline 82 through heart of the sand body –Flattened on top of D-sand (black line) –Base of D-sand.007 to.009 mils below (heavy red line) –Horizon picks cycle through many colors, results in “noisy” attribute maps Frequency range 35 to 85 Hertz Separation of D-sand top and base (isochron) very subtle Separation of frequency bands un-mistakable

6. (303) 429-5425W.C. Overman, MS, Geophysicist6 Slide 6: Instantaneous Frequency Crossline 82 through heart of the sand body –Base of D-sand.007 to.009 mils below (heavy red line) –Time picks still cycle through white to blue often, “noisy” Frequency range 62 to 64 Hertz –All data still present but most frequencies display either white or cyan Separation of D-sand top and base (isochron) very subtle Downward deflection of the white band still obvious

7. (303) 429-5425W.C. Overman, MS, Geophysicist7 Slide 7: D-sand Isochron Map Isochron variation from 0.007 to 0.009 –Variations mapped at below seismic sample rate –See full text for discussion Good correlation between isochron and isopach –discriminates prospective vs. back ground Extends prospective area to NW, along trend Geometry still does not “look” like a sand body

8. (303) 429-5425W.C. Overman, MS, Geophysicist8 Slide 8: Instantaneous Frequency from the Top of the D-Sand pick Experimentation showed “best” presentation from 35 and 55 CPS –Closest agreement with isopach –Least peripheral “noise” All frequencies still present, color for most just set to white Good spatial correlation with isochron map

9. (303) 429-5425W.C. Overman, MS, Geophysicist9 Slide 9: Isochron vs. Frequency Linear relationship of isochron (Slide 7) to frequency (Slide 8). –Lower frequencies with longer time –Higher frequencies with shorter times –Correlation supports validity of sub-sample rate isochron values

10. (303) 429-5425W.C. Overman, MS, Geophysicist10 Slide 10: Isochron “Sweet Spots” Map of narrowly bounded Instantaneous Frequency (62 to 64 Hertz), 4 mils. below the top of the D-sand. –Narrow frequency range eliminates most peripheral events. Maps within the isochron and below the “noise” of the D-sand interface (Slides 5 and 6). “Drill the White and avoid the Cyan.” too simple?

11. (303) 429-5425W.C. Overman, MS, Geophysicist11 Slide 11: IPP vs. Isochron Time, there is a problem… Tests assertions vs. real life results! Color map of Initial Production Potential (IPP) –Green is the color of $ –900+ BOPD NE Sec.21 Isochron time contours –Contoured from Slide 10

12. (303) 429-5425W.C. Overman, MS, Geophysicist12 Slide 12: IPP vs. Structure on the D-sand Top D-sand top depth map, from time structure map. Thick isochron (Slide 11) crosses 40’ low in W ½, Sec. 21. Dry holes were drilled on well control.

13. (303) 429-5425W.C. Overman, MS, Geophysicist13 Conclusions: Peak to Trough attribute could properly locate wildcat –High correlation to Instantaneous Frequency in the south Isochron, though subtle, is a valid and useful attribute –Good visual correlation to isopach –Good numerical correlation to Instantaneous Frequency –Valid mapping at sub-seismic sample rate interval Instantaneous Frequency “best” seismic attribute –Compact geometry –Looks like expected sand body –Excellent correlation with isopach thick –Suggests field extension along trend

14. (303) 429-5425W.C. Overman, MS, Geophysicist14 Conclusions: Peripheral “noise” is reduced by: –limiting frequency display range –selecting time slice within the isochron interval Attribute analysis is not the complete story –Geologic fundamentals are critical –Analysis driven to find attributes which reflect the known geology –Attributes would not find the best IPPs, in sands below seismic resolution. –Strong structural influence on IPPs.

15. (303) 429-5425W.C. Overman, MS, Geophysicist15 Conclusions: Selection of display parameters is critical to analysis Selection of display parameters enhances presentation –Limit display to only data values for best dynamic range –Display limits can be adjusted so as to: increase visual contrast, blank out visual “noise” without altering the data and/or limit presentation to only features of interest.

16. (303) 429-5425W.C. Overman, MS, Geophysicist16 Acknowledgments: Barbara, my wife, for her love and endurance! William C. Cook, Senior Geophysicist, for helpful suggestions upon reviewing the first draft of the full paper. Coerte Voorhies, Sr. Geologist and Account Manager, Seismic Micro Technology, Inc. for his patience with “newbee” questions and his supporting comments regarding this work. Seismic Micro-Technology, Inc., for providing access to The Kingdom Suite of 3D seismic interpretation software, through which this study accomplished.