CARBON DIOXIDE SEQUESTRATION POTENTIAL OF THE WEBER SANDSTONE, UINTA BASIN, UTAH

The eolian Pennsylvanian-Permian Weber Sandstone in the Uinta Basin, Utah, is a promising deep-saline aquifer for geologic CO₂ sequestration in the Colorado Plateau. Geologic characterization of the Weber provides fundamental baseline characteristics to determine the potential to safely and permanently store CO₂ deep underground. Within the basin, the Weber is thick (1000 to 1200 ft), widespread, and deeply buried (14,000 ft in some areas). Nearby outcrops offer analogs for aquifer-facies characteristics and boundaries that affect the overall subsurface Weber heterogeneity. Exploratory wells and the shallow Ashley Valley oil field near Vernal, Utah, supply Weber petrophysical properties and other reservoir data.

Eolian deposits of the Weber Sandstone include dunes, interdunes, and sand sheets. The Weber is a very fine to fine-grained subarkose to quartz arenite. The sand grains are frosted, subangular to subrounded, and well sorted. Based on core analysis, primary (intergranular) porosity in the Weber ranges from 8 to 20%; permeability ranges from 25 to 160 mD. Diagenesis includes carbonate cementation, quartz overgrowths, and authigenic clays. Natural fractures are common, affecting permeability and controlling fluid or gas injection pathways.

The Weber Sandstone intertongues with alluvial redbeds of the Maroon Formation in a zone that passes roughly east-west through the Bonanza area (100 mi²) of the eastern Uinta Basin. In this area, the Weber dips gently northwest toward the basin axis. Together, the structure and stratigraphic relation with the Maroon creates an excellent scenario for CO₂ sequestration in the Weber. We estimate the Weber can store 40 to 50 MMT of CO₂ in the Bonanza area alone.