Methane hydrate decomposition in fluid flow environment: Insights from molecular dynamics simulations

During natural gas hydrate (NGH) extraction, the decomposition of hydrates is always accompanied by gas-water migration. Existing studies have confirmed the significant promoting effect of seawater flow on the decomposition of methane hydrates in porous media sediments. However, the molecular-level structural evolution during hydrate decomposition driven by fluid flow has not yet received broad attention. In this study, molecular dynamics simulation is used to investigate the microscopic effect mechanism of fluid flow on methane hydrate decomposition. Through two different simulation approaches, it is clarified that the accelerated mass transfer of methane molecules from the hydrate surface due to solution flow is the fundamental reason for promoting hydrate decomposition. Additionally, simulations of hydrate decomposition caused by heating and driven by fluid flow above phase equilibrium were performed to trace the microstructural evolution of methane hydrate in these two conditions. Two different modes of hydrate cage rupture were identified, which explain the differences in decomposition rates under different driving factors. The results of this study reveal the decomposition mechanisms of methane hydrates under the fluid flow environment, and may provide theoretical support for the technological solution of water erosion promoting hydrate exploitation. © 2025