Electromagnetic Characterization of CO2 Sequestration Sites – Feasibility Studies and First Field Results from Ketzin

The electrical resistivity of sedimentary rocks depends strongly on pore fluid content and pore connectivity, and bulk resistivity increases where carbon dioxide displaces conductive saline pore fluid. Therefore, controlled-source electromagnetic (CSEM) methods are potentially a key geophysical technique for exploring and monitoring carbon sequestration sites. We investigate the feasibility of CSEM characterization of the CO2 sequestration pilot site at Ketzin, Germany. Simulation studies using newly developed, accurate 1D and 3D modelling tools indicate that surface-based CSEM surveys may well be able to image the background resistivity structure, but will probably not detect the small CO2 reservoir. Borehole-to-surface configurations exhibit much higher sensitivity to the reservoir and may thus be particularly well-suited for monitoring applications. A recently conducted large-scale CSEM field survey has demonstrated the feasibility of CSEM measurements at the site, and provided data that contain subsurface responses down to the target reservoir depth.