Flow modelling to quantify structural control on CO 2 migration and containment, CCS South West Hub, Australia

Abstract

In order to reduce uncertainties around CO 2 containment for the South West Hub CCS site (Western Australia), conceptual fault hydrodynamic models were defined and numerical simulations were carried out. These simulations model worst-case scenarios with a plume reaching a main compartment-bounding fault near the proposed injection depth and at the faulted interface between the primary and secondary containment interval. The conceptual models incorporate host-rock and fault properties accounting for fault-zone lithology, cementation and cataclastic processes but with no account made for geomechanical processes as the risk of reactivation is perceived as low. Flow simulations were performed to assess cross-fault and upfault migration in the case of plume–faults interaction. Results near the injection depth suggest that the main faults are likely to experience a significant reduction in transmissivity and impede CO 2 flow. This could promote the migration of CO 2 vertically or along the stratigraphic dip. Results near the interface between the primary and secondary containment intervals show that none of the main faults would critically control CO 2 flow nor would they act as primary leakage pathways. CO 2 flow is predicted to be primarily controlled by the sedimentological morphology. The presence of baffles in the secondary containment interval is expected to be associated with local CO 2 accumulations; additional permeability impacts introduced by faults are minor. Thematic collection: This article is part of the Geoscience for CO 2 storage collection available at: https://www.lyellcollection.org/cc/geoscience-for-co2-storage