2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 2
Presentation Time: 8:15 AM

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

LI, Xiupeng, College of Geo-Resources and Information, China University of Petroleum, Shandong, 271 Bei-er Lu, Dongying, 257061, China and ZENG, Hongliu, Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin, 10100 Burnet Rd, Bldg130, Austin, TX 78758, hongliu.zeng@beg.utexas.edu

Seismic sedimentology is superior in mapping high-frequency sequences and depositional systems to standard seismic stratigraphic analysis. In the Olmos Formation of Gold River North field, Webb County, South Texas, we identified nine fourth-order sequences from sequence-stratigraphic correlations using 3D seismic and wireline-log data. 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 3-D 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, shelf-edge 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.