Application of three-dimensional fault stress models for assessment of fault stability for CO2 storage sites

Carbon Capture and Storage (CCS) is a key technology for a low-carbon energy future and will have an importantrole on the economic future of the UK Continental Shelf (UKCS). The East Irish Sea Basin (EISB) is a prospectivearea for CCS in the western UKCS. 3D seismic from the EISB were used in this study to characterise the faultnetwork and potential fault reactivation risks associated with CO2injection. Two main structural domains arepresent: a Northern domain with NW-SE faults, and a Southern domain with faults following a N-S orientation.The main storage sites consist of structural closures in Triassic strata of the Sherwood Sandstone Formation(SSF), overlain by alternations of mudstones and evaporites of the Triassic Mercia Mudstone Group (MMG). Theclosures occur predominantly at fault-bounded horsts, with adjacent grabensfilled by thick sequences of theTriassic Mercia Mudstone Group (MMG). The fault framework was used to test, in 3D, the stress model publishedfor the EISB and assess the fault reactivation risk associated with CO2storage. Slip tendency values were pre-dominantly below 0.6, suggesting the presence of stable structures in the EISB. Under the tested conditions,faults are capable of withstanding pressure increases between 3 MPa and 10 MPa before the onset of slip. Thelimited fault reactivation risk suggests CCS operations are suitable prospects for the EISB. This work demon-strates the additional value gained from integration of accurately constrained fault geometries in 3D stressmodels.