A simplified physics model for estimating subsurface CO2 storage resources constrained ‎by fault slip potential

Iman R. Kivi , Silvia De Simone, Sam Krevor

Carbon Capture and Storage (CCS) at rates of several gigatonnes (Gt) per year may be needed ‎to mitigate climate change. However, one major uncertainty is that the risk of injection-induced ‎earthquakes may grow with this scale of deployment. In this work, we develop a tool, named ‎CO2BLOCKSEISM, which uses simplified physics models to screen subsurface storage ‎resources constrained by fault slip potential at regional scales. The tool relies on (1) analytical ‎solutions of the pressure response of saline aquifers to multi-site CO2 injection at time-varying ‎rates and (2) a Monte Carlo-type probabilistic model for evaluating the probability of fault slip ‎incorporating uncertainties in geomechanical variables at the basin scale. Integration of the two ‎modules yields the temporal evolution of slip probability for mapped faults. We validate the ‎approach against seismic activity in Oklahoma caused by basin-wide, low-pressure subsurface ‎wastewater disposal at equivalent rates to large-scale CCS. We show that CO2BLOCKSEISM ‎can capture key features of induced seismicity in this region. We apply the methodology to the ‎southern Utsira Formation, Norway. We find approximately 12.5 Gt CO2 can be stored in this ‎region over 50 years of continuous injection while maintaining the stability of major faults that ‎could otherwise induce felt earthquakes. The use of fault-slip potential as a limiting condition ‎may enable a more restrictive and realistic estimate of the potential for rates of scale-up for ‎CO2 storage regionally and globally.‎