An integrated model for CO2 hydrate formation in sand sediments for sub-seabed CO2 storage

CO2 capture and storage has been considered to be one of the most effective strategies against global warming, among which CO2 storage in deep saline aquifers using the sealing effect of gas hydrate and CO2 storage in the sub-seabed sand sediment in the form of gas hydrate are of great interest nowadays, due to the large capacity of CO2 storage in sub-seabed sand sediments and low risk of CO2 leakage. To access those two options, an integrated model for CO2 hydrate formation, which includes hydrate formation rates on the gas front, on the hydrate film behind the gas front, and on the surface of the sand particles behind the gas front, is proposed in this study to predict hydrate formation morphologies in the sand sediment under the condition of gas-liquid two-phase flow. Then, numerical simulations of CO2 hydrate formation in the sand sediment are conducted, and unknown parameters in the models are determined by comparing the simulation results with experimental data. The simulation results indicate that CO2 hydrate formation on the hydrate film behind the gas front makes a great contribution to CO2 hydrate saturation near the boundary, occupies the pore space of the sand sediment, and results in the permeability reduction and the blockage of the gas flow.