Seismic Monitoring of a Small-scale Supercritical CO2/CH4 Injection - CO2CRC Otway Stage 2C Case Study

CO2CRC Otway project was the first Australian of CO2 geosequestration project. The project site is located 240 km away from Melbourne, Victoria. During the Stage 1 of this project ~66 thousand tons of supercritical CO2/CH4 gas mixture was injected into a depleted gas reservoir at approximately 2 km depth in 2008-2010 to prove that gas can be safely transported and stored in a geological formation. The ongoing Stage 2C of the project is focusing seismic monitoring capabilities and, also, on proving that the injected gas plume plume will stabilize over the period of time. A very limited amount of the same gas mixture (15 000 tonnes) was injected into a saline aquifer at ~1500 m. In order to monitor the gas injection a comprehensive 4D seismic program was rolled out. In this presentation we outline the monitoring program and show the time-lapse seismic results obtained after the first four monitor surveys, acquired at 5 000 t, 10 000 t, 15 000 t of the injection and, also, 9 months after completion of the injection.