A concern in CO2 storage in sub-seabed aquifer is CO2leakage, which may cause impacts on marine organism. To overcome this, storage of CO2 in the form of hydrate in sub-seabed sediments is proposed. By this method, the potential of storage amount is expected to be enlarged as well as the influence on the ecosystem can be reduced. To estimate the capacity and efficiency of this CO2storage option, the formation rate of the hydrate is necessary. Formation of gas hydrate at the interface between gas and water phases consists of two-stages: gas diffusion through hydrate film and hydrate formation at the interface between the film and water. This study aims at modelling of CO2 hydrate formation considering CO2diffusion in hydrate film and at obtaining model constants, such as formation rate and diffusion coefficient. By curve-fitting of calculated and measured heat fluxes, the rate and coefficient were obtained.
One of the concerns in CO2 storage in subsea underground aquifer is a risk of CO2 leakage through direct faults or boreholes and it may cause impacts on marine organism near the leakage sites. Inui and Sato (2006) proposed storage of CO2 in the form of hydrate in subsea underground. The influence on the ecosystem can be greatly reduced because CO2 is made a solid and is stored for a long term. Moreover, the potential of storage amount is about twice as large as the aquifer storage, 18 to 180 billion t-CO2. Ohgaki et al. (1996) also proposed a method to generate heat when CO2 hydrate is formed and to supply the heat to promote the dissociation of CH4 hydrate. Komai et al. (1999) paid attention to the generation of CO2 hydrate at higher temperature and a lower pressure than those for CH4 hydrate, and suggested the production of CH4 by replacement of CO2 hydrate.
