Dynamic Modelling of CO₂ Injection in a Closed Saline Aquifer in the Browse Basin, Western Australia

This paper presents results of dynamic modelling of CO₂ injection in a closed saline aquifer in the Browse Basin, Western Australia. The storage capacity of CO₂ in this type of aquifer is ordinarily greatly limited due to the rapid pressure buildup during injection. This study shows how closed systems, including faulted or lithologically confined reservoirs, may be made suitable for larger volumes of CO₂ storage. Based on the analysis of radial flow models, the inability of the reservoir to accommodate displaced water was considered to be the main reason for the rapid pressure increase. Simulation results show that producing brine from the reservoir can greatly relieve the injection pressure and increase the storage capacity. Under an optimum injection-drainage strategy, the risk of CO₂ breakthrough at the drainage well can be decreased and the cost of draining brine can also be reduced. The studied site is estimated to be able to contain at least 20 years of CO₂ injection, at an injection rate of 1 million tonnes per year, before breakthrough of CO₂ at the drainage well. With this type of drainage strategy, more "closed system" geological sites could be made available for storing CO₂.