--> Abstract: Carbonate Reservoir Characterization Using Seismic Velocity and Amplitude Variation with Offset Analysis: Hardeman Basin, Texas, Test Case, by J. D. Pigott, R. K. Shrestha, and R. A. Warwick; #91004 (1991)

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Carbonate Reservoir Characterization Using Seismic Velocity and Amplitude Variation with Offset Analysis: Hardeman Basin, Texas, Test Case

PIGOTT, JOHN D., and RAJENDRA K. SHRESTHA, University of Oklahoma, Norman, OK, and RICHARD A. WARWICK, Oryx Energy Co., Dallas, TX

Mississippian bioherms in the Hardeman basin, Texas, produce from dolomitized mud cores with porosities that can vary from 10 to 40%. These carbonate buildups, though often similar in seismic reflector boundary configuration, can vary remarkably in reservoir quality (e.g., porosity) owing to diagenesis. However, imaging these lateral variations of porosity and determining the reservoir pressure is possible with detailed seismic velocity control and amplitude variation with offset (AVO) analysis.

The investigated 24-fold seismic profile was acquired by four Vibroseis trucks in the Hardeman basin across two bioherms, one oil-productive and the other tight and water-filled. Detailed stacking velocity analyses on the relative amplitude processed line directly delineate areas of increasing and decreasing gross porosity and dramatically differentiate the two mounds. Moreover, the detailed velocity analyses help provide a more accurate stacked section with resultant better definition of the external mound configuration.

Analysis of available laboratory compressional and shear wave velocity data for carbonate rocks reveal that Young's modulus in carbonates is a function of porosity and differential pressure. Comparison of the derived Young's modulus from an inversion of the AVO data for the unstacked line with the experimental laboratory data yield porosity and differential pressure estimates over the productive bioherm which are within 18% and 15%, respectively, of those observed in the borehole.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)