Groundwater monitoring at the Otway project site, Australia

Abstract The Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) Otway Project in the onshore Otway Basin, Victoria, is Australia’s first pilot project for the long term sequestration of CO 2 . The Otway Project has injected 65,445 tonnes of a mixed CO 2 -CH 4 supercritical fluid (77 mol% CO 2 , 20 mol% CH 4 , 3 mol% of minor wet gases and N 2 ) some 2000 m below the surface into the Waarre Formation, which is capped by the Belfast Mudstone regional seal. The site has been comprehensively characterised by a multidisciplinary team and the risk analysis has shown the likelihood of leakage out of the injection horizon–let alone to the land surface–to be exceedingly low. Nevertheless, the objectives of the CO2CRC through the Otway Project are not only to demonstrate safe CO 2 injection, but also to develop new methodologies for monitoring and verification (MV (ii) monitoring of water levels to determine seasonal variations to formation water flow rate and direction; and (iii) headspace gas sampling of the Dilwyn aquifer to detect tracer compounds and CO 2 content. This monitoring is necessary to establish the connectivity and fluid migration timescales of the fresh water aquifers and to understand the water-rock interactions and resulting fluid composition. The assurance monitoring team works closely with government agencies and landowners and provides data as required. Community engagement has been vital to the success of the program and considerable effort goes toward keeping landowners informed of our activities and minimizing disruption to their properties. To date, the groundwater component of the assurance monitoring program has not detected any perturbation in the baseline condition as a consequence of CO 2 injection. It is important to note that this does not necessarily indicate containment; it does however provide assurance to the community and regulators that the natural resources have not been impacted by the CCS activities and can continue to be used safely.