INTEGRATION OF GEOPHYSICS AND GEOLOGY TO CHARACTERIZE PACIFIC NORTHWEST BASALTS FOR CO2 SEQUESTRATION

Tops and bases of individual flows within the Columbia River Basalt Group in eastern Washington and Oregon may provide one of the highest potential targets for the permanent sequestration of industrial-sourced CO2 in the northwestern United States. Laboratory studies indicate that supercritical CO2 can be injected into these formations and stored over very long timeframes through dissolution, hydrodynamic trapping, and mineralization. The first field validation test of safe and permanent containment of CO2 within these reactive mafic volcanic rocks is being undertaken in eastern Washington as part of the Big Sky Regional Carbon Sequestration Partnership.

The focus of the basalt characterization test is an assessment of the mineralogical, geochemical, and hydrologic impact of injecting 1,000 to 3,000 tons of CO2 within a selected basalt reservoir zone. Specific technical objectives of the test are to: 1) assess the local/large-scale reservoir and adjacent formation responses to injection of supercritical CO2 into deep basalt formations, 2) track migration and evaluate containment of the CO2 for comparison with reservoir modeling predictions, and 3) evaluate the rate of CO2 mineralization for comparison with laboratory-derived predictions. Because basalts pose some of the greatest technical challenges for geophysical-based characterization and monitoring, an aggressive 2D surface seismic program is being accompanied by down-hole vertical seismic profiling (VSP), cross-well seismic tomography, micro-seismic monitoring, wireline logging, geochemical sampling, and detailed hydrologic testing programs.

In this presentation we describe the design and acquisition of the surface seismic survey and the integration of geophysical and geologic technologies being employed to characterize the basalts and to track the movement of the plume and the geochemical changes in the basalts.