CO2 capture and storage (CCS) is one of the most effective countermeasures against the global warming. Although CO2 aquifer storage is considered a main stream as CCS technology, there is a possibility that the capacity of the aquifer storage is limited and may not sufficient to meet the target reduction of CO2 emission. Therefore, it is good to have other CCS options. In this study, we focus on CO2 storage in the form of gas hydrate. In this method, CO2 is injected into the sub-seabed sand sediments at the condition of low temperature and high pressure, under which CO2 hydrate can stably form. A large amount of CO2 is sequestered as hydrate in the sediments by the reaction with pore water. However, hydrate formation has a great risk to reduce permeability and this may lead to the blockage of gas flow. In order to ensure large sequestration space, it is important that gas front expands over a wide area with avoiding such large permeability reduction. In this study, at first, we conducted experiments, in which CO2 was injected into sand sediment and CO2 hydrate formed in the sediment, to understand the blockage phenomena. Next, based on the experiments, we modelled the gas-water two-phase flow with hydrate formation in the sand sediment and developed a one-dimensional numerical simulator. Finally, we simulated the two-phase flow under the experimental conditions and revealed the blockage mechanism due to hydrate formation.
