RESRVOIR CHARACTERIZATION OF THE LOWER SAN ANDRES RESIDUAL OIL ZONE FOR UTILIZATION AND STORAGE OF CARBON DIOXIDE IN COCHRAN AND YOAKUM COUNTIES, TEXAS

Geological storage of carbon dioxide (CO₂) is required for achieving net-zero carbon emissions by the global economy. Incidental storage of CO₂ utilized by enhanced oil recovery (EOR) within residual oil zones (ROZs) in the Permian Basin represents a large opportunity for reducing CO₂ emissions within the energy industry. The open marine to peritidal facies of the San Andres Formation is one of the largest targets for CO₂ storage in the Permian Basin because of intense dolomitization, karst overprinting, and the formation of a large residual oil zone beneath the main reservoir. This study used 300’ of core recovered from the Mammoth Exploration Hudson 601H drill core through the San Andres Formation on the Northwest Shelf of the Permian Basin in Cochran and Yoakum Counties. Eight distinct carbonate facies have been identified through the study of the core from open marine outer shelf to supratidal facies. Petrographic thin section analysis was used to determine porosity types, note diagenetic changes within the ROZ of the core, and provide context for log-based porosity determinations and correlation through the field. Permeability of each of the facies identified in the core was determined with a portable probe permeameter. Together the petrophysical, petrologic, and petrographic observations from the Hudson 601H allow for the development of a reservoir geo-model for the lower San Andres Formation when combined with log data from surrounding wells. This model can be used to both inform future CO₂ utilization projects and geological sequestration projects in the Lower San Andres Formation.