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The AAPG/Datapages Combined Publications Database

GCAGS Transactions


Gulf Coast Association of Geological Societies Transactions Vol. 58 (2008), Pages 623-634

Seismic Sedimentology and Depositional Systems in the Upper Cretaceous Olmos Formation, Gold River North Field, Webb County, South Texas

Xiupeng Li1 and Hongliu Zeng2

1College of Geo-Resources and Information, China University of Petroleum, 271 Bei-er Lu, Dongying, Shandong 257061, China

2Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, 10100 Burnet Rd., Austin, Texas 78758


Seismic sedimentologic analysis is superior to standard seismic stratigraphic analysis in mapping high-frequency sequences and depositional systems. Using 3D seismic and wireline-log data in the Olmos Formation of Gold River North Field, Webb County, South Texas, we identified nine fourth-order sequences from sequence-stratigraphic correlations. Seismic amplitudes can be correlated to log lithologies using 90°-phased seismic data, and, consequently, seismic traces can be interpreted as wireline lithologic logs. Stratal slices made from the 3D seismic volume reveal high-resolution sediment dispersal patterns and associated systems tracts on relative geologic time surfaces. The Olmos Formation in Gold River North field is characterized by two third-order, shelfedge deltaic systems, from which five types of depositional systems were identified:

(1) fluvial plain, which is characterized by fluvial channels, crevasse splays, and swales; (2) deltaic plain, which consists of distributary channels, levees, and crevasse splays; (3) deltaic-front mouth bars and sheet sands; (4) prodelta, which is composed of silty sediments; and (5) incised valleys, which were formed during subsequent lowstand erosion on exposed deltaic sediments. The Olmos Formation can be productive in Gold River North field because distributary-channel sandstones and incised-valley fills may form potentially important stratigraphic traps.

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