--> Abstract: Evaluation Of Gas Reservoirs In Collapsed Paleocave Systems: Ellenburger Group, Permian Basin, Texas, by R. D. Adams, J. W. Collister, D. D. Ekart, R. A. Levey, and M. Nikravesh; #90928 (1999).

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ADAMS, R. D., J. W. COLLISTER, D. D. EKART, R. A. LEVEY, and M. NIKRAVESH
Energy & Geoscience Institute, University of Utah, Salt Lake City, UT

Abstract: Evaluation of Gas Reservoirs in Collapsed Paleocave Systems: Ellenburger Group, Permian Basin, Texas

Image logs facilitate differentiation of two potential primary reservoir types in the Ellenburger Group: 1) collapse breccia and crackle breccia formed by collapse of karst-generated cave systems, and 2) intervals of tectonical ly-f ractu red host rock. Differentiation of these two reservoir types is critical because of differences in overall reservoir geometries and extents, as well as possible differences in production strategies. Image logs also help to differentiate collapse breccia and crackle breccia from other textural facies associated with collapsed paleocave systems, such as cave-fill sediment and unaffected host rock.

Identification of various textural facies associated with collapsed paleocave systems on image logs allows correlation of other log data to the potential primary reservoir zones. Logs utilized include gamma ray, spectral gamma, neutron density, sonic, dual laterolog, and mud gas curves from the mud log. Preliminary results indicate productive intervals in collapse breccia and crackle breccia can be recognized by this approach. Log data are useful in relating seismic data to zones of collapse breccia and crackle breccia.

The present study, funded by the Gas Research Institute (GRI) in partnership with several operating companies, concentrates on reservoirs associated with collapsed paleocave systems. Previous studies funded by GRI have concentrated on tectonically fractured reservoirs.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas