SEGJ Technical Conference

Estimation of CO2 saturation in Nagaoka CO2 Geological Sequestration Project

Abstract Consideration about different types of distribution of CO2 saturation is very important to estimate velocity of partially saturated rocks using Gassmann fluid substitution equation. We have studied sonic log and neutron log obtained at OB-2 well in Nagaoka CO2 geological sequestration project and found that the distribution of CO2 saturation is patchy saturation. Assuming different types of distribution of saturation, we can estimate CO2 saturation for each case uniform, patchy, and Bries formula saturation. Although uniform saturation gives much smaller value than actual saturation, patchy and Bries formula saturation gives reasonable value and the result shows good agreement with CO2 saturation calculated from neutron log.