Molecular mechanism in the solubility reduction of elemental sulfur in H2S/CH4 mixtures: A molecular modeling study
Yuan Wei, Li Wang, Yu Yang, Long Wen, Xiangyu Huo, Li Zhang, Mingli Yang
Abstract
The solubility evolution of elemental sulfur in sour gas is key to study the occurrence and inhibition of sulfur deposition in the exploitation of high-sulfur gas reservoirs. Elemental sulfur mainly dissolves in H 2 S, and its solubility decreases dramatically in the presence of methane. As both methane and H 2 S are the main components in high-sulfur gas, it is essential to understand the molecular mechanism of the solubility reduction in H 2 S/CH 4 mixtures. Molecular dynamics simulations are carried out for the S 8 , H 2 S and CH 4 mixtures to reproduce the solubility reduction upon methane addition, and then used to reveal the reduction mechanism at the level of intermolecular interaction. The simulations reveal that both the strong competitiveness and high collision probability of H 2 S–CH 4 pairs reduce the average densities of H 2 S–S(S 8 ) and H 2 S–H 2 S pairs, which reduce the sulfur solubility in a direct/indirect but cooperative way. The role of methane in the solubility reduction is then discussed and the molecular mechanism of sulfur dissolution and precipitation in the sour gasses is addressed.