Effects of different concentrations of methanol on the decomposition of methane hydrate: insights from molecular dynamics simulations

Abstract

As one of the most promising alternative energy, natural gas hydrate has aroused much attention owing to its controllable exploitation with the aid of chemical injections. Although alcohols are commonly used as promoters for hydrate decomposition, few studies have been carried out to investigate the effect of different concentrations of methanol on methane hydrate decomposition at a molecular level. For the first time, we systematically combined the parameters of angular order parameter (AOP), radial distribution function (RDF), and mean square displacement (MSD) to reveal the role of methanol in the decomposition mechanism of methane hydrates through the molecular dynamics approach. The results demonstrated that methanol concentration had an optimal value for hydrate decomposition, which was 20% methanol solution for the best efficiency for the hydrate decomposition and had been examined by analyzing the parameter of AOP. This can be attributed to the promotion effect of methanol on the deconstruction of the hydrogen bond networks of water molecules and the inhibition effect of methanol on the mass transfer effect of methane diffusion, both of which determined the decomposition of methane hydrates. These effects were further quantitatively evaluated by the structural parameters of RDF and MSD. The obtained results reveal the important influence of methanol concentrations on methane hydrates decomposition on molecular scale, and provide useful guidelines for highly efficient exploitation of natural gas hydrate reservoir.