The ideal site for geologic CO2 sequestration has several key characteristics. Specifically, an aquifer must be available with high permeability, poor water quality (three to four times the salinity of seawater), and adequate depth to maintain the CO2 in a supercritical state. In addition, conditions must preclude the lateral or vertical migration of stored gases or their escape from the sequestration zone. M&A provided hydrogeologic expertise to target an appropriate geologic horizon for a pilot drilling and testing program in northern Arizona. We used a GIS-based approach to analyze regional geologic and groundwater quality conditions and then develop recommendations for potential CCS targets. A site near the APS Cholla Power Plant near Joseph City was selected for the study.

M&A oversaw the geologic and hydrologic logging of a nearly 4,000-foot-deep pilot well, which was drilled using conventional mud-rotary methods in 2009. Testing indicated that although water at this depth was of suitably poor quality for sequestration, the target geologic unit did not have the required permeability for injecting and storing CO2. Plans are underway to drill another test hole on Hopi lands, near Black Mesa.

M&A provided technical assistance to obtain several permits for the project: a drilling permit from the Arizona Oil and Gas Conservation Commission, a temporary aquifer protection permit from ADEQ, and an underground injection-control permit from the EPA for a planned pilot test.