Reservoir Geophysics Research Program


Characterization of Dispersion, Attenuation, and Anisotropy at the Buena Vista Hills Field, California


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Southwest Research Institute (SwRI) created a log of intrinsic dispersion and attenuation for the Antelope Shale formation of the Buena Vista Hills field, San Joaquin Valley, California. High dispersion (or low Q) values correlate with thin sand and carbonate beds within the Antelope Shale. These beds are at least 10 times as permeable as the host shale formation, so this effect provides a possible avenue for seismic prediction of permeability. The dispersion log is formed through comparison of crosswell seismic velocities (measured at approximately 1 kHz) and sonic log velocities (measured at approximately 10 kHz).


To provide a proper basis for comparison, the sonic log must first be adjusted for field anisotropy, scaling effects, and resolution of measurement. We estimated a local shale anisotropy of about 20% based on correlations generated from published measurements of other shale fields. Resolution enhancement to capture the thin sand and carbonate beds and windowed Backus averaging completed the process of matching measurement scales. A modeling study verified the technique, and showed that beds of thickness greater than 30 cm have a measurable signature. The actual resolution is on the order of the crosswell Fresnel length, or about 7 meters for the model study.


For more information about the characterization of dispersion, attenuation, and anisotropy, or how you can contract with SwRI, please contact Jorge O. Parra, Ph.D., at jparra@swri.org or (210) 522-3284.




Contact Information

Jorge O. Parra, Ph.D.

Reservoir Geophysics

(210) 522-3284



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August 07, 2014