Coupled Modelling of CO2 Injection into a Realistic North Sea Aquifer

The work describes the use of coupled reservoir simulation geomechanical modelling to investigate the potential for geomechanical failure within a saline aquifer subjected to CO2 injection for geological storage. The model was based on a realistic North Sea (Forties Sandstone) formation. The work was carried out as part of the UK Storage Appraisal Project and was mainly concerned with issues of injection pressure, injectivity and thereby storage capacity. The default criterion within the project was to consider a maximum injection pressure based on (hydraulic) fracture pressure gradient. The geomechanical modelling work was carried out to see if there was any scope to change this based on other potential modes of geomechanical failure. The results show that for the scenarios modelled, geomechanical failure is unlikely in the formation providing the injection rate is controlled so that the injection pressure does not exceed the fracture pressure at the well.