Print this pageWAHLMAN, G. P.1, J. A. SIMO3, D. R. TASKER2, M. L. STOKLOSA3, and J. L. BEALL4
1Amoco, Houston, Texas
2Amoco Bolivia, Santa Cruz
3University of Wisconsin, Madison
4University
of Texas, Austin
Abstract: Lower Permian (Wolfcampian) Carbonate Shelf-margin Buildups in the Hueco Mts., West Texas: Analogs for Permian Basin Reservoirs
Hueco Group (Wolfcampian) carbonate shelf-margin complexes exposed in the western outliers of the Hueco Mts., west Texas, are excellent outcrop analogs for some subsurface Wolfcampian reservoirs in the adjacent Permian Basin. The Hueco Mts. exposures have an overall shallowing-upward succession consisting of four sequences, each with a seaward- and landward-stepping package. Bioherms in the shelf-margin complexes are constructed by phylloid algae, calcisponges heliosponges, Tubiphytes, bryozoans, and laminar encrusting algae. Relative abundances of community components vary with the paleogeographic and stratigraphic positions of the bioherms. Thick skeletal grainstone-packstone shoal facies, with enclosed Tubiphytes-dominated patch reefs, flank and cap the bioherms.
Similar biohermal and shoaling facies form Hueco Limestone subsurface reservoirs on the eastern margin of the Central Basin Platform in the Permian Basin, e.g., South Cowden (8790 Canyon) Field, Ector County, Texas. Facies variations have a strong influence on reservoir distribution and quality. The subsurface bioherms have the same biotic composition as above, but also often have abundant botryoidal radial fibrous cements. Thick flanking and capping grainstone-packstone shoals form the primary reservoir facies, having intergranular, intragranular, and skelmoldic porosity ranging in excess of 20%. More mud-rich biohermal facies have skelmoldic, vuggy, and fracture porosity in the 8-10% range, and more variable permeability.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas