AAPG Foundation 2019 Grants-in-Aid Projects

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A Diagenetic Sequence for the Wolfcamp Formation, Implications for Hydrocarbon Potential

Abstract

This study aims to identify differences in the way that diagenesis has altered different facies of the Wolfcamp Formation, a major U.S. shale play located in the Midland Basin of West Texas, and the implications for the extractability of the play. Facies models based on lithologic core description and geochemical analysis have already been described and represent a variety of deepwater slope to basin plain depositional environments and benthic redox conditions (Luna and Birgenheier, in review). Using these facies models, petrographic examination of ultrathin thin sections and scanning electron microscope images of two Wolfcamp cores will be performed. Grain and matrix composition and morphology will be observed and characterized, along with cross-cutting relationships of mineral phases, and pore volume and geometry. Based on observed cross-cutting relationships, a comprehensive timeline of diagenetic events for the Wolfcamp (i.e., a paragenetic sequence) will be developed by facies. Tight-rock analysis to obtain porosity and permeability values of select core plugs will be completed by facies. These values will be compared to the established diagenetic model in order to correlate observations about porosity and permeability with lab-measured values. While the Wolfcamp is estimated to be the most prolific hydrocarbon accumulation in the United States, little is known about facies heterogeneity and the properties of each facies which could affect horizontal well success. Establishing a diagenetic sequence of each facies will allow for scientifically informed drilling rather than statistical exploitation of the play.