Laboratory Measurement of Geophysical Properties for Monitoring of CO2 Sequestration

Both seismic and electrical properties depend on the mineralogical composition of the rock, porosity, fluid content, and in situ stress state. Previous work on effects of CO2 on seismic velocities is limited. Wang and Nur, 1989, measured both compressional (Pwave) and shear (S-wave) velocities on a number of sandstones saturated with nhexadecane and then flooded with CO2. They made measurements at different pore pressure and temperature conditions, finding that CO2 caused P-wave velocities to substantially decrease under all conditions while S-wave velocities were decreased at high pore pressure and increased at low pore pressures. Wang et al, 1998, found that both Pand S-wave velocities decreased in a carbonate rock when CO2 was injected at pore pressures from 1200 psi to 2600 psi.