Investigation of ice evolution during methane hydrate dissociation at different initial temperatures in microporous media

Abstract

In this work, a coupled lattice Boltzmann model is proposed to study the gas hydrate dissociation with consideration of ice evolution in microporous media. The reliability of this model is verified by simulating the dissociation of xenon hydrate and the freezing of water droplets, respectively. The initial temperature is one of the influences on methane hydrate dissociation. In this paper, methane hydrate dissociation and ice evolution characteristics have been analyzed at the initial temperature of 270.5 K–278 K. Within this temperature range, a maximum percentage of methane hydrate dissociation can be obtained near the freezing point. Ice formation inhibits and delays the methane hydrate dissociation at the initial stage. It is demonstrated that for the whole process, heat release caused by the ice-water mixture formation facilitates methane hydrate dissociation. However, the ice formation stage has negative impacts on hydrate dissociation time. Additionally, the whole dissociation can be divided into four processes by analyzing the evolution of dissociation percentage and ice saturation. Especially, three types of ice formation positions are concluded. They are related to the hydrate structure and occurrence state. This paper provides a reference of the effect of ice evolution on methane hydrate dissociation in practical applications.