<div>We have investigated whether water-saturated residual oil zones (ROZs), sometimes associated with conventional Australian hydrocarbon plays, could provide a CO2 storage resource and supplement depleted field storage. Our petrophysical study demonstrates 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. Multiphase compositional flow modelling was used to estimate the CO2 storage efficiency of typical Australian ROZs. We developed a novel modelling methodology that first captures oil migration events leading to the formation of ROZs. Modelling CO2 storage over a 20-year injection period demonstrates that CO2-oil interactions increase the density and viscosity of CO2, enhancing CO2 sweep efficiency and lateral flow, improving storage efficiency. The extent of these effects depends on the quantity and spatial distribution of residual oil in place and the miscibility of CO2 at reservoir conditions. Presented at the Australian Energy Producers (AEP) Conference & Exhibition (https://energyproducersconference.au/conference/)

The Exploring for the Future program Showcase 2024 was held on 13-16 August 2024. Day 3 - 15th August talks included: <b>Session 1 – Hydrogen opportunities across Australia</b> <a href="https://youtu.be/pA9ft3-7BtU?si=V0-ccAmHHIYJIZAo">Hydrogen storage opportunities and the role of depleted gas fields</a> - Dr Eric Tenthorey <a href="https://youtu.be/MJFhP57nnd0?si=ECO7OFTCak78Gn1M">The Green Steel Economic Fairways Mapper</a> - Dr Marcus Haynes <a href="https://youtu.be/M95FOQMRC7o?si=FyP7CuDEL0HEdzPw">Natural hydrogen: The Australian context</a> - Chris Boreham <b>Session 2 – Sedimentary basin resource potential – source rocks, carbon capture and storage (CCS) and groundwater</b> <a href="https://youtu.be/44qPlV7h3os?si=wfQqxQ81Obhc_ThE">Australian Source Rock and Fluid Atlas - Accessible visions built on historical data archives</a> - Dr Dianne Edwards <a href="https://youtu.be/WcJdSzsADV8?si=aH5aYbpnjaz3Qwj9">CO2: Where can we put it and how much will it cost?</a> - Claire Patterson <a href="https://youtu.be/Y8sA-iR86c8?si=CUsERoEkNDvIwMtc">National aquifer framework: Putting the geology into hydrogeology</a> - Dr Nadege Rollet <b>Session 3 – Towards a national inventory of resource potential and sustainable development</b> <a href="https://youtu.be/K5xGpwaIWgg?si=2s0AKuNpu30sV1Pu">Towards a national inventory of mineral potential</a> - Dr Arianne Ford <a href="https://youtu.be/XKmEXwQzbZ0?si=yAMQMjsNCGkAQUMh">Towards an inventory of mine waste potential</a> - Dr Anita Parbhakar-Fox <a href="https://youtu.be/0AleUvr2F78?si=zS4xEsUYtARywB1j">ESG mapping of the Australian mining sector: A critical review of spatial datasets for decision making</a> - Dr Eleonore Lebre View or download the <a href="https://dx.doi.org/10.26186/149800">Exploring for the Future - An overview of Australia’s transformational geoscience program</a> publication. View or download the <a href="https://dx.doi.org/10.26186/149743">Exploring for the Future - Australia's transformational geoscience program</a> publication. You can access full session and Q&A recordings from YouTube here: 2024 Showcase Day 3 - Session 1 - <a href="https://www.youtube.com/watch?v=Ho6QFMIleuE">Hydrogen opportunities across Australia</a> 2024 Showcase Day 3 - Session 2 - <a href="https://www.youtube.com/watch?v=ePZfgEwo0m4">Sedimentary basin resource potential – source rocks, carbon capture and storage (CCS) and groundwater</a> 2024 Showcase Day 3 - Session 3 - <a href="https://www.youtube.com/watch?v=CjsZVK4h6Dk">Towards a national inventory of resource potential and sustainable development</a>

This Record forms part of a study under the Exploring For The Future (EFTF) program (2020-2024). The Residual Oil Zone Project was designed to understand and identify residual oil zones in Australia, with the aim of developing this potential hydrocarbon and CO2 geological storage resource through CO2–Enhanced Oil Recovery. The work presented here is a collaborative study between Geoscience Australia and GeoGem Consultants. Residual Oil Zones (ROZ) represent a new and potentially viable oil resource for Australia, while at the same time providing a means to use and store carbon dioxide (CO2) through the application of CO2 enhanced oil recovery (CO2-EOR). These naturally water-flooded and water-saturated reservoirs, which contain a moderate amount of residual oil, can be associated with conventional fields (brownfields) or occur with no associated main pay zone (greenfields). Both types of ROZ are currently produced commercially through CO2-EOR in the USA, and are of growing interest internationally, but have not yet been explored in Australia. CO2-EOR has been in widespread practice in the USA since the oil shocks of the 1970’s. While tertiary CO2 injection usually targets oil remaining in fields that have been subject to water-flooding, there has been a parallel adoption of practices to recover vast amounts of paleo-oil that existed when many of these reservoirs were much fuller, before relatively recent (in geologic time) events caused structural and seal changes, resulting in natural water-flooding and/or migration of much of the oil out of the reservoir. The Permian Basin in Texas contains many examples where such Residual Oil Zones (ROZ’s) were found beneath conventional oil reservoirs. These ROZ are unproductive to conventional water flood operations but offer the possibility of an extra 9-15% recovery (of the ROZ OIP at discovery). This work reviews the lessons or insights that can be gained from the USA regarding ROZ field developments.

The Lower Cretaceous Gage Sandstone is a deep saline aquifer which is overlain by the regionally extensive Lower Cretaceous South Perth Shale seal in the offshore Vlaming Sub-basin, Perth Basin, Australia. This paper is focused on the CO2 storage capacity estimation in the Gage reservoir by integrating both the well and seismic data. After a 3D grid system was constructed, well log interpretations, depth converted interval velocity and seismic relative acoustic impedance data were imported into the 3D grids. The volume fraction of shale was first constructed combining the neural networks modelling and residual stochastic simulation from the well and seismic attributes data. Porosity was modelled using sequential Gaussian co-simulation with the volume fraction of shale model. The CO2 storage capacity was estimated using the total pore volume and storage coefficients in US-DOE methodology. The best estimate (P50) of carbon storage capacity in the Gage Sandstone reservoir is 493 million tonnes based on the static reservoir modelling. This article was submitted to Energy Procedia November 2018. <b>Citation:</b> Liuqi Wang, Megan Lech, Chris Southby, Irina Borissova, Victor Nguyen, David Lescinsky, <i>CO2 storage capacity estimation through static reservoir modelling: A case study of the lower Cretaceous Gage Sandstone reservoir in the offshore Vlaming Sub-basin, Perth Basin, Australia, </i>Energy Procedia, Volume 154, <b>2018</b>, Pages 54-59, ISSN 1876-6102, https://doi.org/10.1016/j.egypro.2018.11.010.