抄録
Carbon dioxide capture and storage (CCS) is expected to be a key decarbonization technology for achieving carbon neutrality. Sensitivity analyses using an energy system model on CCS costs and storage capacity indicate that increasing domestic CO2 storage capacity is economically rational. To increase CO2 storage capacity, we have devised a method of subseafloor CO2 storage using clathrate hydrates (hereinafter referred to as CO2 hydrate storage). CO2 hydrate storage is a method of storing CO2 by forming an artificial hydrate seal within the subseafloor strata, utilizing the property of CO2 to generate hydrates under the low-temperature and high-pressure conditions of the deep-sea around Japan. Numerical simulations of CO2 hydrate generation show that more than half of the injected liquid CO2 dissolves into formation water, while the remainder is ultimately stored in the formation by the hydrate seal. Regarding storage costs, estimation performed with QUE$TOR 2020 indicates that CO2 hydrate storage is less expensive than aquifer storage, because even though the depth from sea-surface is greater, the injection location beneath the seafloor is shallower, resulting in lower well drilling costs.
