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Dr. William A. Ambrose


Depositional History and Stratigraphic Evolution of the Midway to Carrizo Succession on the
Western Margin of the Houston Embayment, Southeast Texas

11:30 AM Wednesday, January 15, 2020
at the Cascades
4511 Briarwood Road
Tyler, TX 75709

Cost: $25


A detailed study of the upper Midway, Wilcox, Sabinetown, and Carrizo stratigraphic succession in a large, 13,770-mi2 (~35,660-km2) area updip and along the Wilcox shelf margin in the southeastern Texas Gulf Coast, interprets and maps 20 high-frequency, fourth-order regressive-transgressive sequences. The study demonstrates that the Midway-to-Carrizo stratigraphic succession contains greater variability in depositional systems, facies, and reservoir sandstone-body geometry than previously documented. By integrating core and outcrop with net-sandstone maps from wireline-log data, it also provides evidence of pervasive tidal processes throughout most of the Wilcox-to-Carrizo succession. Previous studies of the Wilcox Group in southeastern Texas interpreted primarily fluvial-dominated, wave-modified deltaic systems from thick (commonly >600-ft [>183-m]), undivided stratigraphic intervals that encompass multiple depositional episodes. In contrast, this study demonstrates that sandy depositional axes are narrow (<3-mile [<4.8-kilometer]) and exhibit complex, anastomosing geometries consistent with tidal and fluvial systems. Consequently, both vertical and lateral complexity of sandstone bodies in the Wilcox-to-Carrizo stratigraphic succession is more complex than previously documented, implying a greater potential for reservoir heterogeneity.


William A. Ambrose
Bureau of Economic Geology
The University of Texas at Austin


William A. Ambrose is a Senior Research Scientist at the Bureau of Economic Geology. He received a Master of Arts degree in geological sciences in 1983 from the University of Texas at Austin. Since joining the Bureau of Economic Geology in 1987, he has worked on a variety of projects at the Bureau, including characterization of the Woodbine Group in the East Texas Basin, Pennsylvanian reservoirs in the Eastern Shelf of the Permian Basin, Frio fluvial and deltaic reservoirs in South Texas, tight-gas reservoirs in the Cleveland Formation in the Texas Panhandle, co-production of gas and hot brine from Oligocene reservoirs in the Texas Gulf Coast, evaluation of coalbed methane reservoirs in Rocky Mountain basins, and reservoir characterization and basin analysis studies in Venezuela and Mexico. He is currently the principal investigator of the Bureau’s STARR (State of Texas Advanced Oil and Gas Resource Recovery) program, past president of the Energy Minerals Division (EMD) of AAPG, chair of the EMD Coal Committee, and co-chair of the AAPG Astrogeology Committee. His contact information is--email: , telephone: 512-471-0258, address: Bureau of Economic Geology, The University of Texas at Austin, University Station, Box X, Austin, TX, 78713-8924.