Abstract

Stockyard field produces oil from the Permian (Leonardian) Upper Clear Fork and Glorieta Formations of the northern Central Basin Platform, west Texas. Hydrocarbon entrapment is the result of structural drape of the reservoir interval over a basement uplift generated during the Marathon-Ouachita Orogeny. This pre-Permian structural high provided positive paleobathymetric relief that influenced the distribution of marine and peritidal environments during Clear Fork-Glorieta deposition. Peritidal and shoal sediments were preferentially deposited across the crest of the structural high while subtidal sediments accumulated within the deeper waters of the adjacent structural lows. The reservoir interval is partitioned into a progradational set of eleven parasequences that reflect superimposed short- and long-term periods of accommodation change during deposition. Parasequences are comprised of a shallo wing-up ward facies succession that typically includes from base to top: non-reservoir subtidal, reservoir-prone shoal, and capping non-reservoir peritidal. Reservoir quality is controlled both by parasequence-scale facies disconcontinuity, and diagenetic overprint. The highest reservoir quality is associated with shoal facies that were preferentially subjected to a coarsely-crystalline phase of dolomitization. Future strategies of infill development, recompletion, and enhanced oil recovery should take into account parasequence-scale flow units to maximize recovery efficiency.