Seismic Monitoring of CO2 migration through a shallow fault

Abstract To investigate gas migration along a near-surface fault and assess the performance of various seismic monitoring techniques, a controlled shallow CO2 release experiment was carried out at the CO2CRC Otway International Test Centre (Victoria, Australia). Sixteen tonnes of CO2 were injected at ~70 m depth into the Brumbys Fault. The monitoring program combined reverse 4D VSP using a downhole sparker source with a dense surface geophone array, cross-hole seismic tomography with distributed acoustic sensing (DAS), passive DAS analysis of Rayleigh-wave amplitudes, and data from permanently deployed surface orbital vibrators (SOVs). All methods detected the evolving plume consistently and provided complementary information on its geometry and migration. The results demonstrate that the integrated monitoring framework is capable of resolving small-scale CO2 movement and can be scaled up for continuous, cost-effective surveillance in larger storage projects.