Experimental and numerical studies on dissociation of methane hydrate by simultaneous injection of nitrogen and hot water

This study aims to investigate the targeting behavior of a gas phase consisting of multicomponent and gas-water multi-phase flow assumed in an in situ low-temperature oxidation (LTO) process as an enhanced gas recovery from a methane hydrate (MH) reservoir. Experimental and numerical studies on MH dissociation in porous media by simultaneous injection of N₂ and hot water were carried out. It can be confirmed based on experimental results that the equilibrium temperature as a result of the decrease of the molar fraction of methane gas (CH₄ ) in the gas phase with N₂ injection was maintained at a lower level so that dissociated CH₄ production was completed earlier. In addition, based on the experimental observation of change of equilibrium temperature, the interfacial model of MH for the estimation of fugacity change was constructed and introduced into the numerical model. The history matching for temperature change, permeability characteristics, and CH₄ production during simultaneous injection process was subsequently conducted. Through the optimization of each parameter, it was found that the calculated results could reproduce a series of behaviors quantitatively. As a result, from the view-point of the behavior of the gas phase consisting of multicomponents on MH dissociation, the validity of a numerical model developed for an in situ LTO process has been confirmed.