Environmental impact assessment technologies for sub-sea geological CCS: Perspective of prediction models

Carbon capture and storage (CCS) is a potentially effective counter measure against global warming. CO ₂ storage in deep saline aquifers using the sealing effect of gas hydrate is of great interest nowadays, due to the large capacity of CO ₂ storage in sub-seabed sand sediments and low risk of CO ₂ leakage. In this method, the leaked CO ₂ rises into sub-seabed sand sediments under high pressure and low temperature, allowing stable CO ₂ into a hydrates to form. To access this option, a series of numerical models are proposed in this study to predict CO ₂ migration and hydrate formation in the sand sediment under the condition of gas-liquid two-phase flow in both reservoir scale and microscopic scale. This study can also provide tools to know where hydrate is formed in the pore of porous media and to reveal the mechanism of permeability reduction due to hydrate formation.