Geomechanical Aspects of CO2 Geological Storage Design in a Multi-Layered Depleted Field in Offshore Malaysia

Abstract An integrated study was conducted to design the injection plan for a CO2 geological storage site offshore Malaysia. The selected site is a multi-layered depleted field in a faulted anticlinal structure. The geomechanical aspects of the design consisted of a field-scale geomechanical model to investigate the integrity of the caprock and stability of the faults under different subsurface conditions imposed by the CO2 injection and storage. The field consists of thirteen depleted reservoir and seven aquifer layers, which were selected as potential storage layers. The geomechanical related risks of CO2 storage in these layers were investigated in detail using a coupled numerical approach between a reservoir dynamic flow model and a geomechanical simulator. The results of the numerical modelling were used to investigate the caprock integrity, including the effects of thermal stresses on the caprock and reservoir, and the risk of reactivation of existing faults in the caprock and reservoir for all studied CO2 storage layers. The integrity of the caprocks immediately above the selected CO2 storage layers was analyzed using the results of the coupled geomechanical simulations. The results show that the final pressures in the storage layers do not exceed the fracture pressure in the caprock above any of the storage layers. Hence, the planned injection pressure is unlikely to cause any tensile failure in the caprocks. The fault stability analysis was conducted for the critical faults within the zone of interest. These results also show no risk of fault instability with the current injection design. Considering the recent focus of industry on the management of carbon emissions, the case study presented in this paper is one of the best practices that can be implemented for field-scale geomechanical risk assessments to evaluate long- and short-term CO2 injection and storage during the planning phase.