Abstract

The next several decades pose enormous challenges and opportunities for the global oil and gas industry. While oil and gas will continue to be used for decades to come, it is now recognized that enormous quantities of CO2 have to be stored in subsurface geologic formations to reach global decarbonization goals. International bodies, countries (including China and the United States the world’s two largest greenhouse gas emitters), and 25% of Fortune 500 companies have all established net-zero emission goals by mid-century. In this talk, I will focus on several geomechanical issues that have to be 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 some other issues that 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 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 too small to induce fault slip. Second, when utilizing depleted oil and gas reservoirs for long-term storage of CO2, it is important to understand both the mechanical changes of the reservoir rocks and the stress changes that resulted from depletion. Such knowledge is required to predict how pressure (and the 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.