Molecular Dynamics Study on the Growth Mechanism of CH ₄-H ₂S Binary Hydrates

Abstract

In the exploitation of gas reservoirs with high sulfur, the frequent formation of gas hydrates will seriously affect the exploitation and pipeline transportation of natural gas. Therefore, the study of the formation mechanism of CH₄-H₂S hydrates  is helpful to take effective measures to solve the problem of hydrate plugging in gas reservoirs with high sulfur. In this study, the growth mechanism of CH₄-H₂S hydrates the temperature of 250-285 K, the pressure of 5-50 MPa and H₂S concentration of 15%-75% was studied by using molecular dynamics simulations. The results indicate that temperature has a great influence on the growth of CH₄-H₂S hydrates, where the maximum growth rate is about 2.25 Å/ns at the temperature of 260 K. The pressure has a negligible impact on the growth rate of CH₄-H₂S binary hydrates . The growth rate of CH₄-H₂S hydrates increases as H2S concentration increases. The ratio of gas/water of H₂S molecules is greater than that of CH₄ molecules, indicating that H₂S molecules are more easily adsorbed by the interface. Furthermore, the total number of cages occupied by H₂S molecules is greater than that of CH₄ molecules, which suggests that the structure of binary hydrates is mainly stabilized by H₂S molecules.

Keywords: Molecular dynamics, CH4-H2S binary hydrates, Growth rate