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

Stage 2C of the CO2CRC Otway Project: Seismic Monitoring Operations and Preliminary Results

The CO2CRC's “Otway Stage 2C project” is a test injection of 15,000 tons of supercritical gas mixture (80 mole% CO2 & 20 mole% CH4) at the CO2CRC Otway site in the Australian state of Victoria. The objective of this test is to examine the limits of surface seismic detection and to conduct detailed pressure monitoring of the injection. A key design feature of the project is injection near the bottom of a highly permeable formation, thereby allowing for buoyancy driven flow to thicken the plume and enhance seismic response. The project is specifically targeting observation of the development of the gas plume through a combination of multi-vintage 4D seismic surveys acquired with a buried seismic receiver array, 4D Vertical Seismic Profiling (VSP) and pressure measurements. Using both time-lapse seismic data and reservoir simulations, we aim to not only detect the plume but also demonstrate its eventual stabilisation. In this paper we discuss the technical aspects of the Otway Stage 2C seismic monitoring program and the initial results