Sub-seabed sequestration of CO2 is a potential method for reducing the atmospheric level of greenhouse gas. The geological exploitation in sub-seabed hydrate zone shows that free gas could be sealed beneath it, which provides a feasible idea for CO2 sub-seabed sequestration. In this study, the CO2 was injected into the water-containing porous media to simulate the CO2 sub-seabed sequestration process, and the magnetic resonance imaging (MRI) technique was employed to recognize the real-time reservoir state. The CO2 hydrate formed during the CO2 upward migration process and produced sealing effect for external fluids. In addition, it was found that at least 8 MPa of overpressure can exist stable beneath the CO2 hydrate cap, which ensures the security of CO2 marine sequestration and increases the CO2 sequestration depth. These results indicate that the hydrate cap provides a feasible and safe method for CO2 geological sequestration, and it is significant to promote the potential of sub-seabed CO2 sequestration.
Keywords CO2 sequestration, hydrate cap, sealing effect, MRI