Joint Rock Physics Inversion of Seismic and Electromagnetic Data for CO2 Monitoring at Sleipner

Abstract

The Carbon Capture and Storage project that is taking place at the Sleipner field involving the injection of CO2 into Utsira sandstone reservoir at 1012 m below sea level. The migration of CO2 must be monitored to understand the amount and composition of CO2 inside the reservoir. The goal of this study is to estimate petrophysical parameters such as CO2 saturation and its mixing type inside the reservoir by jointly inverting P-wave velocity and resistivity model.

CO2 saturation estimated from joint rock physics inversion can reach 68% with an uncertainty of around 20%. The same test also shows that the Brie exponent for CO2 higher than 15% is of around 7, suggesting the mixing type of brine and CO2 is somewhere between uniform and patchy. These results are variable depending on the chosen parameters. The study shows that two different geophysical methods can be combined to provide complementary information for discrimination of CO2 saturation and its mixing type.