Regional geomechanical response to large-scale CO ₂ storage in the Bunter Sandstone, UK Southern North Sea

The Bunter Sandstone Formation is the intended storage formation for several commercial CO ₂ storage projects in the UK Southern North Sea. Previous studies have highlighted the potential for regional pressure perturbations expected to impact an area far beyond the storage sites where CO ₂ will be contained by structural trapping. This study evaluates the potential geomechanical impacts associated with widespread pressurisation of saline aquifers, based on a coupled flow-geomechanical modelling study. A published industrial-scale scenario is used as the basis for a reservoir simulation study, which envisages storage of 232 Mt, divided between four sites over a period of 30 years. Several scenarios are considered, with the worst-case scenario resulting in the greatest pressure increases selected for input to a geomechanical model. The results indicate that the saline aquifer is expected to experience only very small strains and gentle uplift of the seabed as a consequence of the modelled injection loads, with minimal risk to containment or other adverse impacts associated with rock failure. The large, well-connected nature of the saline aquifer ameliorates the potentially negative impacts of excessive pressurisation. The modelling results suggest that the Bunter Sandstone is an excellent prospect for commercial-scale storage of CO ₂ from a geomechanical perspective.