AAPG Foundation 2019 Grants-in-Aid Projects

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Diagenetic Controls on Reservoir Characteristics of the Wolfcamp and Bone Spring Formations in the Delaware Basin, West Texas

Abstract

Understanding the processes and products of diagenetic alteration is key to successful exploration and production of unconventional reservoirs within mixed carbonate-siliciclastic systems. Previous studies have shown evidence for a complicated diagenetic history in the Delaware Basin, West Texas due to burial, fluid flow, tectonic stresses, and overpressuring. This study aims to determine the main geologic controls on diagenesis and their impact on reservoir porosity, thermal maturity, and hydrocarbon migration, focusing on the basin-centered, unconventional successions from the Wolfcamp and Bone Spring Formations. Investigation of cores exhibiting differences in reservoir performance, structural setting, and fracturing history allows for hypotheses on whether diagenesis in these settings occurred under open-system or closed-system conditions. Petrographic and fluid inclusion microthermometric analyses will be supplemented with δ13C and δ18O stable isotope analysis, 87Sr/86Sr strontium isotope analysis, and laser ablation U-Pb dating to: 1) develop a detailed paragenetic sequence for the diagenetic events; 2) evaluate the relationship between diagenetic events and tectonic, hydrologic, and sequence stratigraphic controls; and 3) determine the control exerted by these geologic processes on the occurrence and distribution of reservoir properties. The results will be used to constrain the burial and thermal history of the region and to develop a conceptual diagenetic model for the controls on reservoir behavior and performance. A better understanding of the diagenetic history of the Bone Spring and Wolfcamp will aid in predicting spatial and temporal trends in reservoir character within the Delaware basin, as well as similar heterogeneous, unconventional basins elsewhere.