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Depositional Processes, Sequence Stratigraphic Framework, and Reservoir Quality of the Wolfcamp A Formation in the Delaware Basin, West Texas


The Delaware Basin, located in southeast New Mexico and west Texas, is the westernmost sub-basin of the Permian Basin. With an estimated 24 BBL of recoverable oil, the lower Permian Wolfcamp Formation is one of the most productive unconventional petroleum systems in the United States and is characterized by significant lateral and vertical heterogeneity in a mixed carbonate-siliciclastic system. Understanding the depositional processes, sequence stratigraphic framework, and petrophysical parameters associated with the reservoir facies in the lower Permian Wolfcamp Formation has major implications to maximizing hydrocarbon production.

Wolfcamp lithologies vary from calcareous and non-calcareous organic-rich mudstones to grainstones, conglomerates, and breccias. Wolfcampian gravity-flow deposits are sourced from a semi-arid, mixed carbonate-siliciclastic shelf and were deposited in a slope to basinal setting. The deposits are comprised of non-cohesive turbidites, cohesive debris flows, and hybrid flow events. These deposits are likely driven by global sea-level fluctuations associated with the growth and ablation of continental ice during the Permian icehouse conditions. During these periods of eustatic fluctuation, increased siliciclastic deposition occurred during low-stands, and carbonate deposition dominated high-stands as carbonate detritus was shed off of the adjacent Central Basin Platform.

This study evaluates the reservoir quality of two Wolfcamp A cores from the north Texas portion of the Delaware Basin and how the reservoir quality in these cores varies on a sub-meter scale as a result of depositional processes and diagenetic alteration. Depositional analogs to sedimentation occurring in the Wolfcamp A (i.e. debris flows, turbidites, hybrid flow events) will help constrain the expected potential reservoir geometry and distribution. The integration of datasets, which include cores, thin sections, wireline logs, and laboratory measured petrophysical properties, will determine the reservoir quality of the Wolfcamp A. The pore system architecture will be analyzed using ion milled samples under the SEM and laboratory measured sonic velocity analysis. Additionally, rebound hardness will be analyzed and tied to facies, stratigraphic architecture and reservoir quality.