A large amount of refrgeration capacity is required for the formation of CO₂ hydrate due to the emission of reaction heat. This fact leads to the unfeasible facet of onboard production of hydrate. Author introduced the new method of hydrate formation utilizing the vast low temperature capacity of deep sea water without addition of the extra energy to CO₂. The well stirred mixtures of CO₂ liquid and sea water are lead to the injection pipes installed vertically toward the deep sea. The fluid is cooled down through the pipe wall below the level of 10°C necessary for the hydrate formation and the further stirring is given to the fluid at a few appropriate positions of pipe depth. During these process formation rate is heightened to the full level. After being deposited on the sea bottom very long term stability is considered to be vitally essential items for the storage of hydrate. Author studied analytically the hydrate decomposition accompanied with CO₂ diffusion through the hydrate caused by the molecular density gradient. The upper and lower limits of hydrate decomposition for a hundred years were indicated under some numerical assumptions as well as the temperature change of hydrate. R-11 (CCl₃F) hydrate experiments were carried out, and the formation, decomposition and phenomena at the interface of both liquids were observed.