Modelling CO2 EOR-storage in Residual Oil Zones

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 petrophysical study to identify and characterise ROZs. In this report, we model the formation of a residual oil zone in an Australian setting and the subsequent injection of CO2 using a 5 spot well pattern. The reservoir is built as an archetype example of the Hutton Formation from the Cooper-Eromanga basin. The reservoir interval is populated with "permeable sandstone” and “impermeable baffle” facies and a sealing layer at the top of the model is created and assigned properties such that it can be made to leak oil by capillary failure, as part of the process used to create a residual oil column. The static model is them imported into CMG-GEM software for the reservoir flow simulations. We find the scenario, with injectors perforated at the top and a central producing well perforated at the bottom, able to both store the most CO2 and produce the most oil. The storage and sweep efficiencies are high, highlighting the difference with typical CO2 storage scenarios without pressure mitigation. 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.

Data is available on request from clientservices@ga.gov.au - Quote eCat# 149366