Natural methane hydrates are estimated to be the largest source of unexploited hydrocarbon fuel. Understanding the dissociation of methane hydrates in the flow system is vital for natural gas development, especially for the gas hydrate reservoir protection and the prevention of secondary hydrate generation in the wellbore. In this work, the model of natural gas hydrate in clay mineral pores was established, and the effects of drilling fluid on hydrate stability under different intrusion velocities were investigated by molecular dynamics simulation. The simulation results show that the hydrate nucleus on hydrophilic surfaces will be more susceptible to temperature. As the temperature increases, the hydrate nuclei at the edges and corners collapse preferentially due to the large contact area. Water molecules on hydrophilic surfaces are difficult to participate in the formation of hydrates due to hydrogen bonds. Furthermore, the higher the velocity of the fluid, the greater the degree of hydrate dissociation. And the hydrate nucleus decomposes faster in the vertical flow direction than that in the parallel flow direction. The destruction of hydrate formation and decomposition equilibrium is the main reason for hydrate decomposition in the flow process. These results contribute to a better understanding of hydrate decomposition in a flowing system and implications for developing new materials for high-performance hydrate drilling fluids.
