Seismic and strain detection of heterogeneous spatial distribution of CO2 in high- permeable sandstone

Abstract In this study, we attempt to clarify the heterogeneous CO 2 distribution in homogeneous and high-permeability porous sandstone (Mt. Simon sandstone: 105 mD) using both physical rock experiments and fluid mechanical analyses. In particular, the experiments involve CO 2 injection into porous sandstone with measurements of P-wave velocity ( V p ) and strain under low capillary number ( C a ) flow conditions. We set three V p -measurement lines and two strain gauges (vertical and horizontal) at the center of the core. We also monitor changes of flow rate, volume, and differential pressure between the two pumps during CO 2 injection. The V p values of all channels show slight changes (under 4%). By contrast, the strain measurements indicate a substantial expansion in both directions. It is proposed that the injected CO 2 reaches the counter end of the core specimen immediately and forms few large-percolation clusters in porous sandstone. The CO 2 that follows flows only through clusters as pathways without capillary resistance. These CO 2 flows produce spatially heterogeneous distributions of CO 2 in the porous sandstone and make it difficult to monitor and detect CO 2 by seismic wave velocities only.