An optimisation strategy to maximise the CO 2 storage capacity utilisation of a deep saline aquifer is presented in this paper. This was achieved by a scenario of simultaneous CO 2 injection and brine production within the Forties sandstone. The optimisation was performed using the SIMPLEX and Generalised Reduced Gradient algorithms and the assistance of surrogate modelling techniques. Results have shown that, by using five brine production wells producing up to 2.2 Mtonnes/year, the CO 2 storage capacity of the reservoir can be increased by 125% compared to when no brine production is used. It is also observed that pressure constraints are the main limiting factors controlling further CO 2 injection.