Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Regional Stratigraphic and Rock Characteristics of Eagle Ford Shale in Its Play Area: Maverick Basin to East Texas Basin
(1) Bureau of Economic Geology, The University of Texas at Austin, Austin, TX.
The potential play area of the Upper Cretaceous Eagle Ford Shale (EFS) extends for at least 400 mi from the Texas-Mexico border northeastward to the East Texas Basin. Observations of the variations in lithostratigraphy, thickness, and depth trends of the EFS in this area provide a first approximation of potential producing areas. The EFS comprises two units in the Maverick Basin/Rio Grande Embayment area. The upper EFS, which exists solely south of the San Marcos Arch, consists of interbedded low- and high-gamma-ray burrowed and calcareous mudrock. In contrast, the more organic-rich, lower EFS, characterized by generally high gamma-ray values, extends continuously from South Texas across to the northeast flank of the San Marcos Arch. Only the lower EFS crops out southwest of the East Texas Basin and northeast of the Maverick Basin. The Eagle Ford interval, thickest in the Maverick Basin, gradually thins to a minimum over the arch. It continues from the northeast flank of the arch into the southwest East Texas Basin, where the sandstone-rich Woodbine Group occurs between Eagle Ford Group and Maness Shale. With facies pinch-out of the Woodbine complex and its equivalent Pepper Shale on the basin’s southwest flank, however, the Eagle Ford mudrock lies directly above the Maness. Depths of the southeast-dipping lower EFS range considerably from outcrop to ~17,000 ft (~5,180 m) at the Stuart City shelf margin on the northeast flank of the San Marcos Arch. Regional depth gradients of the unit are greatest on the flanks and crest of the San Marcos Arch.