Numerical Simulation of Fault Compartmentalisation in CCS Reservoir

To improve the South West Hub Carbon Capture and Storage Project (Western Australia) site characterisation and reduce uncertainties around CO2 capacity, injectivity and containment, conceptual fault hydrodynamic models are defined, and reservoir simulations are carried out to investigate the CO2 plume development and its interaction with faults. The conceptual fault hydrodynamic models are defined to incorporate host rock and fault properties accounting for fault zone lithology, cementation, and cataclastic processes. The primary focus was to study the impact of different faulting depth scenarios on reservoir compartmentalization and across-fault and up-fault migration of CO2. Selected flow simulations in the lower injection unit highlight a transition from partially sealing to totally sealing faults that occurs for the most probable faulting depth scenarios. This suggests some degree of compartmentalization in the injection unit resulting in potential restriction of reservoir volume affecting the plume distribution with a preferential CO2 migration aligned along the local N–S structural trend. The compartment bounding faults however, are expected to be composed of overlapping segments unlikely to represent extensively continuous barriers and lateral flow pathways are expected to intermittently exist between compartments reducing risk of pore pressure build up at depth.