Rock Mechanics and Coupled Processes

The recognition that enormous quantities of CO2 have to be stored in geologic formations to reach the global decarbonization goals, a number of geomechanical issues have to considered to ensure long-term storage efficacy. While it has been long recognized that changes in reservoir pressure should not exceed the pressure at which hydraulic fracturing might occur of seal formations, this presentation will focus on a number of other issues have not been sufficiently addressed. First, it is important to identify potentially active faults to limit the possibility that injection-related increases in pore pressure could induce seismic, or aseismic, slip on already-known faults. Also, as existing evidence shows that potentially active faults (and the damage zones that surround them) are permeable, the presence of potentially active faults represent possible leakage pathways that should be avoided, even when injection-related pressure changes are quite small. Second, when considering utilizing depleted oil and gas reservoirs for long-term storage of CO2, it is important to understand the both mechanical changes of the reservoir rocks and the stress changes that resulted from depletion. Such knowledge is required to predict how pressure (and poroelastic stress changes) associated with CO2 injection will affect the reservoir. Finally, from the perspective of induced seismicity, it is critically-important to identify reservoirs with both top seals and bottom seals to avoid pressure communication to potentially active faults in the basement.