Active-seismic monitoring of pore pressure changes in an analog reservoir

Geophysical monitoring of pore pressure diffusion in geologic carbon sequestration reservoirs is critical for understanding hydraulic processes occurring within the reservoir. Yet geophysical monitoring efforts to date are limited to tracking the evolution of the CO₂ plume throughout the reservoir and the caprock. We used CASSM (Continuous Active Source Seismic Monitoring), a time-lapse seismic technique, to monitor travel-time changes caused by pressure perturbations in a laboratory-scale, analog reservoir called SMARTT (Seismic Monitoring of an Analog Reservoir Testing Tank). CASSM was able to capture the subtle changes in pressure caused by multiple water injections into the reservoir. The correlation between perturbations in travel-time and pressure was up to 0.997 (R²) depending on the source-receiver pair. We used a granular contact model to show that these travel-time perturbations were a result of reservoir pressure changes caused by injection.