Geologic Evaluation of the Tucson Basin for Carbon Dioxide Sequestration Potential

The Department of Energy (DOE), including its National Energy Technology Laboratory and West Coast Regional Carbon Sequestration Partnership (WESTCARB), have established national programs to evaluate the technical feasibility of long-term subsurface geologic storage of carbon dioxide (CO2) produced by industrial activity. The WESTCARB is a consortium of seven western U.S. States and one Canadian Province that is one of seven regional North American partnerships established to evaluate technical aspects of high-volume CO2 capture and sequestration. Collaborative WESTCARB research programs have included more than 90 public agencies, private companies, and non-profit organizations. The Arizona Geological Survey (AZGS) began work in 2010 on WESTCARB Phase III – Arizona Geological Characterization (California Energy Commission Agreement Number 500-10-024). As part of WESTCARB Phase III, the AZGS is evaluating the potential for CO2 sequestration in geologic formations that are below a level of 800 meters (m) (2,625 feet (ft)) depth below land surface (bls). This evaluation is directed at porous and permeable geologic formations with impermeable sealing strata in Cenozoic sedimentary basins in the Basin and Range Province, and Paleozoic sedimentary formations of the Colorado Plateau. An initial screening of Cenozoic sedimentary basins with significant depth and volume below the 800 m (2,625 ft) bls level resulted in 10 candidate basins from a total of 88 basins (Spencer, 2011). This report represents ongoing WESTCARB assessment of CO2 storage potential in the Tucson basin, one of 10 Cenozoic basins in Arizona identified during the preliminary evaluation, and is part of Tasks 2 and 3 of Arizona WESTCARB Phase III. Task 2 consists primarily of characterizing basin structure, stratigraphy, lithology, and the nature of seals or a cap rock. This task also includes determining the storage capacity of permeable sediments below 800 m (2,625 ft) depth (Spencer, 2011). Task 3 is to determine if, and at what depth, saline groundwater approaches 10,000 milligrams per liter (mg/L) of total dissolved solids (TDS), characterized in a separate salinity study (Gootee et al., 2012). This concentration represents the threshold above which water is considered non-potable and unsuitable as drinking water (United States Environmental Protection Agency 1991). Based on the extent of permeable strata underlying impermeable strata, saturated with saline groundwater above 10,000 mg/L, the CO2 storage volume below 800 m (2,625 ft) can be revised from earlier estimates (Spencer, 2011).Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu