AN INTEGRATED APPROACH TO UNDERSTANDING DEPOSITIONAL ENVIRONMENTS AND PROCESSES IN WOLFCAMPIAN SHALE, WEST TEXAS, PERMIAN BASIN

The Early Permian Wolfcamp Shale of the Permian Basin in West Texas is a mixed siliciclastic-carbonate, unconventional resource play with considerable potential. Increased interest in petroleum exploration of Wolfcampian strata in the basin has sparked fundamental research into the sedimentological, petrophysical, and geochemical signatures preserved in the subsurface and their correlation to depositional environments and well log interpretation.

Two environments, lower slope and basin plain, are identified based on the abundance and distribution of lithofacies, grain-size, detrital carbonate content, level of bioturbation, and amount of skeletal material. The abundance and distribution of gravity flows also serve as a useful proxy in determining distance from the shelf margin. In these settings quartz and kerogen accumulated in the basin interrupted by episodic deposition of shelf to basin-floor carbonate debris flows. While these traditional views seem to be operative, there is also evidence for a broader range of biological and physical processes than is commonly acknowledged. These depositional processes resulted in compositional and grain-size heterogeneities and accumulation of the thick organic-rich shale targets.

Characterization of Wolfcamp reservoir quality and potential is complicated by lateral and vertical, small-scale heterogeneities. This study incorporates a representative core, and core data, from within the current Wolfcamp play area in order to relate reservoir attributes to depositional environments and processes. The goal of this research is to demonstrate how techniques of identifying and linking depositional facies to reservoir quality, and tying these to wire-line log data, assist in the evaluation of unconventional reservoirs and enhance the predictability of reservoir potential away from core observations.