AAPG Foundation 2019 Grants-in-Aid Projects

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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 in New Mexico and west Texas, is the westernmost sub-basin of the Permian Basin. The lower Permian Wolfcamp Formation is one of the most productive unconventional petroleum systems in the US 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 reservoir facies has major implications for maximizing hydrocarbon production. These slope to basinal gravity-flow deposits (turbidites, debris flows, and hybrid flow events) were sourced from a semi–arid, mixed carbonate–siliciclastic shelf. Lithologies vary from calcareous and siliciclastic organic–rich mudstones to grainstones, conglomerates, and breccias. Sedimentation is likely driven by global sea–level fluctuations during Permian icehouse conditions, with increased siliciclastic deposition occurring during low-stands, and carbonate deposition dominating high-stands. This study evaluates the reservoir quality of two Wolfcamp A cores from the north Texas portion of the Delaware Basin and how it varies on a sub-meter scale as a result of depositional processes and diagenetic alteration. Depositional analogs to sedimentation in the Wolfcamp A will constrain the expected reservoir geometry and distribution. The integration of datasets (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.