Geological and petrophysical appraisal of residual oil zones in onshore Australian basins

Maintenance and Update Frequency: asNeeded | Statement: This product is a key output from the Residual Oil Zone CO2 storage study under the EFTF program (2020-2024), completed under contract number 006410 between GA and CSIRO. It follows a preliminary methodology report (eCat 145932) and is associated with a reservoir modelling study (in review). | Purpose This product is an output of the CO2 Storage in Residual Oil Zones project that was conducted through the Exploring for the Future program (2020-2024). | Geoscience Australia and CSIRO have collaborated, under the Exploring for the Future program, to investigate whether water-saturated residual oil zones (ROZs), sometimes associated with conventional Australian hydrocarbon plays, could provide a CO2 storage resource and enhance the storage capacity of depleted fields. This product is part of a larger project that includes, among others, a reservoir modelling component. This report focuses on our petrophysical module of work that investigated the occurrence and character of ROZs in onshore Australian basins. Our findings demonstrate that ROZs occur in Australia’s hydrocarbon-rich regions, particularly in the Cooper-Eromanga Basin. ROZs with more than 10% residual oil saturation are uncommon, likely due to small original oil columns and lower residual saturations retained in sandstone reservoirs than in classic, carbonate-hosted North American ROZs. Extensive, reservoir-quality rock is found below the deepest occurring conventional oil in many of the fields in the Eromanga Basin, potentially offering significant CO2 storage capacity. For more information about this project and to access the related studies and products, see: https://www.eftf.ga.gov.au/carbon-co2-storage-residual-oil-zones.