Cretaceous and Tertiary strata across Mississippi, Alabama, and the adjacent continental shelf constitute a widespread succession of sandstone, mudstone, and carbonate that have proven to be important objectives for deployment of geologic CO2 storage technology in saline formations. Analyses of stratigraphy, sedimentology, and reservoir properties indicate that the Cretaceous-age Paluxy Formation, Washita–Fredericksburg interval, and lower Tuscaloosa Group may provide a 1.4 gigatonne storage opportunity at the Kemper County Energy Facility in east-central Mississippi. The marine Tuscaloosa shale is a widespread reservoir seal in the deep subsurface of Mississippi and Alabama, and detailed geologic investigation of the shale includes integrated analysis of geophysical well logs and core that have yielded a multiscale analysis of the confining strata. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), quantitative X-ray diffraction (XRD), and permeability analyses from core were used to interpret microfabric, pore types, mineralogy and fluid properties within mudstone of the east-central Mississippi Embayment. This study has importance for identifying potential migration of fugitive CO2 into or across the shale. Results indicate that mudstone in the marine Tuscaloosa shale is an effective confining unit that is a key component of the storage complex in Kemper County. Water saturation in the marine Tuscaloosa shale units promotes rock ductility and contributes to low permeability, which is on the order of 10–100 nanodarcies (nD) as determined by pressure-decay permeametry. Accordingly, the marine Tuscaloosa shale is interpreted to prevent significant cross-stratal migration of injected CO2 from deeper sandstone reservoirs.
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