HYDROGEOLOGIC CHARACTERIZATION OF A CO2 INJECTION PILOT BOREHOLE WITHIN THE COLUMBIA RIVER BASALTS

Continental flood basalts may play an important role in sequestering regional sources of CO₂. Particularly noteworthy attributes of basalts include their geochemical reactive properties with CO₂, and their presence in regions where sedimentary basin capacity may be limited. There are little available data, however, on the injection capacity and sealing ability of these basalt formations. In preparation for a pilot basalt CO₂ field injection study, a series of hydraulic tests were performed during drilling and following completion of a 4110 ft test borehole in the Columbia River Basalt Group. A downhole packer/pressure probe test system was used to isolate test intervals that were characterized during drilling. Additional hydrogeologic information was obtained from surface and borehole geophysics, and core and groundwater samples. Based on the hydraulic and hydrochemical (i.e., non-potable) characterization information obtained during drilling, a ~190 ft injection zone was selected. Additional, more extensive hydraulic tests and hydrochemical sampling of the selected injection zone were also conducted following well completion.