Planning Time-lapse CSEM-surveys for Joint Seismic-EM Monitoring of Geological Carbon Dioxide Injection

Using state of the art survey planning and modeling tools, we investigate the possibility of employing marine controlled-source electromagnetic (CSEM) surveys in the monitoring of carbon dioxide sequestration. As a site example, we use the CO2 injection from the Sleipner Øst gas field into the Utsira formation in the North Sea. The injection plume inferred from 3D seismic surveys is used, together with well information and a priori geological knowledge, to build resistivity models for CSEM modeling. We find that the time-lapse change in the CSEM response would have been well above CSEM-acquisition noise levels in both 2001 and 2006. The combination of CSEM and seismic methods, which have a complementary dependence of their response on residual brine saturation, can yield an improved resolution of the CO2-distribution. In addition, CSEM methods are sensitive to the bulk volume of a resistor, also complementary to the superior resolution in seismics. We therefore would expect CSEM monitoring to become a valuable addition to the current monitoring program.