Numerical simulation of the effect of gas hydrate formation on liquid-CO2 leakage suppression in sub-seabed sand sediment

CO2 capture and storage is a promising strategy against global warming. Although there is concern about the risk of CO2 leakage from deep saline aquifers, it is expected that CO2 hydrate formation suppresses the leakage in the sub-seabed sediment, depending on the water depth of a storage site. Therefore, hydrate formation in the sub -seabed sand sediments is one of key factors in lowering the risk of CO2 leakage and it is important to know conditions under which CO2 leakage is suppressed by hydrate formation. To estimate the sealing effect of CO2 hydrate against CO2 leakage beneath the seabed, a numerical simulation method of hydrate formation in sand sediments can be a useful tool. The simulation results suggest that, under the given conditions, it was shown that the sealing effect due to the hydrate formation can be expected, except for the case of an absolute permeability of 10-12 m, at which leaked CO2 can reach the seafloor for all the leakage rates tested in this study. From these results, it is suggested that whether CO2 hydrate suppresses the leakage of liquid CO2 mainly depends on the absolute permeability of a selected sea area.