NOVELTY - Method-1 for creating a carbon dioxide hydrate, comprises: (a) supplying liquid carbon dioxide and a dissociation agent to a hydrocarbon hydrate; (b) decomposing the hydrocarbon hydrate by the dissociation agent into a hydrocarbon gas and liquid water; and (c) forming the carbon dioxide hydrate from the liquid carbon dioxide and the liquid water.    USE - The method is useful for: creating carbon dioxide hydrate in a subterranean geological formation, in which the hydrocarbon hydrate is located; releasing a hydrocarbon gas from a hydrocarbon hydrate in a geological formation (claimed); and depositing carbon dioxide (carbon dioxide sequestration) in and collecting hydrocarbons from subterranean geological formations.    ADVANTAGE - The improved method: is based on liquid phase reaction, which has increased conversion rate when compared with the conversion based on solid state diffusion; replaces hydrocarbon hydrate by carbon dioxide hydrate with an increased reaction rate and an improved conversion efficiency; releases hydrocarbon gas from the subterranean geological formation in a controlled manner without destabilizing the geological formation; and is capable of completely replacing the hydrocarbon hydrate by the carbon dioxide hydrate thus avoids the stability problems in the geological formation. The improved deposition device is compatible with conventional borehole techniques and deposition devices.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a method of releasing a hydrocarbon gas from a hydrocarbon hydrate in a geological formation, comprising: the steps of (a) and (b) as above per se, and delivering the hydrocarbon gas to a surface of the geological formation;    (2) a substance composition, which is provided for depositing carbon dioxide hydrate in a subterranean geological formation (3), comprising liquid carbon dioxide, and an agent that is capable of facilitating the dissociation of the hydrocarbon hydrate; and    (3) a deposition device (100), structured and arranged for depositing carbon dioxide hydrate in a subterranean geological formation, comprising a mixing device (10) structured and arranged for providing a mixture of liquid carbon dioxide and the dissociation agent, and a supply device (20) structured and arranged for supplying the mixture of the liquid carbon dioxide and the dissociation agent into the subterranean geological formation.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic illustration of creating a carbon dioxide hydrate by a liquid phase reaction.    Subterranean geological formation (3)    Mixing device (10)    Stirring device (13)    Supply device (20)    Deposition device. (100)