A WORKFLOW FOR DOWN-SELECTING A CCS SITE

The Gulf of Mexico (GoM) Basin has widely-recognized potential to participate in the emerging low carbon economy. Many GoM coastal carbon-intensive industries (e.g., petrochemicals, LNG, etc.) require decarbonizing via capture. Fortunately, the geologic section provides many opportunities to store captured CO₂. In order to obtain a Class VI EPA permit for injecting non-EOR-related CO₂ into deep saline reservoirs, the geologic section must be well-characterized and understood. Based on several studies, including one in the Lower Rio Grande Valley, we provide a workflow designed to yield permit-ready locations that can accept and store large volumes of CO₂ for significant time periods. Arguably, one of the most important decision points in the workflow is identification and qualification of a storage complex for geologic storage. Along most of the Texas coast, both onshore and offshore, the Miocene age geologic section is most prospective because it is generally below the minimum depth for dense-phase CO₂ and above the depth to over-pressure. Ubiquitous potential storage reservoirs (e.g., barrier-bar and deltaic depositional systems) and confining systems are identified in the Miocene section. The depositional systems are interpreted from well log character and mapping sand body geometry. The geologic structural interpretation includes mapping faults on available 2-D and 3-D seismic and inferring regional extent. Whole core is planned to calibrate conversion of log-based porosity to permeability in the Miocene of this region, as well as confirm the low permeability of fine-grained zones (e.g., marine mudstones). Critical characteristics of the storage complex include 1) lateral continuity of flow units across facies trends and across faults, 2) recharge of shallow aquifers with brine from saline mudflats leading to absence of a fresh groundwater resource, and 3) relatively shallow occurrence of overpressure that locally limits the depth of the injection window.