Dissociation behavior of hydrate core sample using experimental apparatus equipped with long core holder

Natural gas hydrate that exists in the sediment is thought to constitute a large methane gas reservoir and is expected to be an energy resource in the future. In order to make recovery of natural gas from hydrates commercially viable, hydrates must be dissociated in-situ. Inhibitor injection method is thought to be one of the effective dissociation method as well as depressurization and thermal stimulation. But there is only limited information about dissociation kinetics in inhibitors, while there exist substantial phase equilibrium data. In our previous study, the experimental set-up had been developed to achieve the precise thermal analysis. The length of the core holder had been extended to 5 times longer to reproduce the thermal gradient in the core. In this study, the dissociation behavior of a hydrate core sample in methanol aqueous solution has been investigated using the developed experimental set-up. Warm methanol aqueous solution was injected through the core samples, which imitate natural gas hydrate sediment under seafloor. This approach could make clear that the specific feature of dissociation behavior using inhibitor injection. Temperature change was rather different from the case of water injection that made the hydrate dissociate fast. Also mass transfer at down stream was cleared that could not be detected by previous experimental apparatus. Recrystallization was observed.