Geophysical Monitoring of Shallow CO2 Controlled Release Experiment: Otway Project Field Case Study

The talk will cover the results of the seismic monitoring program of the shallow CO2 controlled release experiment into a shallow strike-slip fault at the CO2CRC Otway International Test Centre in Victoria, Australia. Understanding how faults influence fluid migration behaviour is crucial, and the project provides valuable empirical insights on carbon dioxide flow within vertical faults. Approximately 16 tonnes of gaseous CO2 were injected at a depth of ∼77–87 meters. This experiment offered an opportunity to obtain field measurements on vertical fault permeability at a shallow strike-slip fault. The geophysical monitoring program employed several downhole high-resolution seismic techniques to observe this fast-developing process, including active reverse VSP, active cross-hole seismic with DAS and passive monitoring with DAS using oceanic microseisms. The applied seismic techniques successfully detected and observed the injected carbon dioxide and its evolution during the monitoring program. The seismic monitoring program highlighted the effectiveness of downhole seismic methods for rapid data acquisition to capture fast-evolving processes. Time-lapse reverse VSP provides a 3D volumetric view of gas distribution patterns through heterogenic near-surface sediments. Meanwhile, time-lapse cross-hole seismic and passive monitoring using DAS proved efficient for detecting CO2 presence at critical locations.