Molecular Dynamics Simulation of Decomposition of Methane Hydrate and Interfacial Characteristics in Nanostructure Region

Abstract

Methane hydrate decomposition is crucial to its safe and efficient exploitation and utilization. The water-methane hydrate–water system in the nanostructure region during decomposition process was studied by molecular dynamics simulation. Taking the decomposition of 3 × 3 × 6 SI hydrate at an initial temperature of 310 K as an example, the decomposition processes of different layers at different moments were studied. The density distribution of methane molecules, radial distribution function of water molecules in each layer and F3 order parameter of each layer during the decomposition process were analyzed. The locations of hydrate–water interfaces at different temperatures and different moments were estimated, and furthermore the decomposition rate of hydrate was obtained. In addition, this work is also concerned with the influence of hydrate–water interfacial contact area on decomposition. It is noticed that hydrate decomposes row by row from outside to inside. The formation of methane nano-scale bubbles is observed during decomposition. Due to the increase of the heat and mass transfer resistance, the decomposition rate becomes slower with time. However, higher initial temperature is helpful to promote the decomposition rate. Besides, expanding hydrate–water interfacial contact area can enhance the hydrate decomposition efficiently.