Seismic Inversion for Shale Gas/Oil within the Austin Chalk and Eagle Ford Shale, Maverick Basin, South Texas
Ogiesoba, Osareni; Eastwood, Ray; Ambrose, William A.; Hammes, Ursula
For several decades, the Austin Chalk has been known to constitute a good hydrocarbon play, containing more than 2,000 horizontal wells. However, some of these wells have been unsuccessful because, either they did not penetrate hydrocarbon sweet spots or hydrocarbon-source-rock distribution within and outside the chalk was unknown. In this project, we conducted seismic inversion studies by combining seismic data with wireline logs to determine sweet spots and predict resistivity distribution (using the deep-induction log) within the Austin Chalk and Eagle Ford Shale in South Texas.
Our investigations show that >90% of productive zones within the Austin Chalk are in the lower Austin Chalk and are associated with Eagle Ford vertical-subvertical en echelon faults, suggesting hydrocarbon migration from the Eagle Ford Shale. Furthermore, the quality-factor attribute (Q) can serve as a tool for detecting high-water saturated zones. Although Q was not selected as one of the primary attributes for predicting resistivity, it nevertheless can serve as a good reconnaissance tool for predicting resistivity and brittle zones.
In addition, local accumulations within the Austin Chalk may be related to Austin TOC-rich zones or migration from the Eagle Ford through fractures. Wells that have high water production do so because the water-bearing middle Austin Chalk that sits on the downthrown side of Eagle Ford regional faults constitutes a large section of the horizontal well, as evidenced by the Q attribute. Finally, the lower Austin Chalk and upper Eagle Ford Shale together appear to constitute a continuous (unconventional) hydrocarbon play.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013