ABSTRACT: Where is the Lower Leonard Shelf? A Depositional Model for the Blalock Lake Southeast and Powell 8300 Fields, Glasscock County, Texas

HIGHSMITH, DEBRA L., S. W. Exploitation, Midland Producing Division, Texaco Exploration and Production, Midland, TX, and LOUIS H. TAYLOR, Geotechnical Services, Western Exploration Division, Texaco Exploration and Production, Denver, CO

Lithofacies and microfacies analysis of reservoir rocks from the Blalock Lake Southeast field indicate in-situ mound and intermound facies. Mounds grew on remnant Strawn paleohighs across a broad carbonate ramp. Two-dimensional seismic sequence stratigraphy does not confirm a well-defined shelf margin. Rocks from the Powell 8300 field are grainstone and debris-flow facies sourced from the

adjacent mounds of the Blalock Lake Southeast field. We recognize six major lateral facies in the two field areas: the mound facies, a flanking crinoid mudstone, apron talus, intermound peloidal mudstones, capping grainstones, and downdip grainstone and debris flows. This depositional model also includes a globally documented eustatic sea level fall in the overall transgressive upper Wolfcamp-lower Leonard cycle. The perpendicular depositional trends of the mound facies and the grainstone-debris-flow facies are useful tools that can be applied to exploratory and development efforts.

AAPG Search and Discovery Article #91018©1992 AAPG Southwest Section Meeting, Midland, Texas, April 21-24, 1992 (2009)