This report represents the first output from a study designed to understand and identify residual oil zones in Australia, with the aim of developing this potential resource using CO2 –EOR techniques. This work is part of the Residual Oil Zone (ROZ) module in the Exploring For The Future (EFTF) programme, which runs from 2020-2024. The work presented here is a collaborative study between Geoscience Australia and CSIRO.
ROZ potentially represent a new and viable oil resource for Australia, while at the same time providing an additional CO2 storage avenue through application of CO2 enhanced oil recovery (CO2-EOR). These water-saturated reservoirs, which contain a moderate amount of residual oil and resemble water-flooded conventional oil fields, 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 Permian Basin, USA, and are of growing interest internationally, but our understanding of ROZ in the Australian context is lacking.
The first section of this report identifies and discusses the key parameters and factors that influence the efficiency with which ROZ can be produced. These include fluid-rock and fluid-fluid interactions, which may affect injectivity and sweep of hydrocarbons. We also discuss the effects of reservoir heterogeneity as it relates to flow dynamics and also the effects of pore space configuration. The first section concludes with a discussion of CO2 storage associated with ROZ development. In the second section, we discuss two different injection strategies with which to develop ROZ; carbonated brine injection and water alternating gas injection.
The final section outlines details of the workflow that will be applied in the EFTF ROZ module over the coming years. Our proposed workflow is a three pronged approach which involves core flooding experiments, pore scale modelling and petrophysical analysis to identify potential ROZ in key Australian basins. In addition to plain CO2 injection, two other promising EOR techniques namely CO2-WAG and carbonated brine injection are also considered in this workflow. The main objectives of this workflow are to:
• assess and identifying estimated oil recovery potential from a target ROZ by either of three EOR injection strategies,
• identify the best injection strategy for a ROZ
• identify the CO2 storage and utilization potential
