CO₂ Geological Storage Using the Clathrate Hydrate

Abstract

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.