Sulfur solubility in sour gas components and mixtures from a molecular perspective

The solubility characteristics of sulfur in sour gas are crucial in addressing the issue of sulfur deposition and comprehending the multiphase flow behavior in high-H2S gas reservoirs. To this end, a pioneering molecular simulation method was proposed in this study to investigate the dissolution of sulfur in sour gas at the molecular scale. The solubility of sulfur in methane (CH4), carbon dioxide (CO2), hydrogen sulfide (H2S) and their mixtures were quantified. Additionally, the microscopic dissolution process of sulfur was elucidated and its differences among different gas components were highlighted. The results show that H2S is the predominant component that facilitates the dissolution of sulfur in sour gas. More specifically, the density in the central region of the sulfur phase diminishes linearly with the escalation of sulfur solubility in the H2S component. Meanwhile, the density at the edge of the sulfur phase increases linearly, and the thickness of the transition zone of the sulfur phase tends to increase initially and then remain constant. As temperature and pressure rise, the interaction energy between H2S molecules and sulfur augments, resulting in the entry of more gas molecules into the central region of the sulfur phase. Consequently, a smaller sulfur-sulfur intermolecular interaction energy ensues, leading to an increase in sulfur solubility. Similarly, the difference in solubility of sulfur among CH4, CO2, and H2S is also attributed to the variation in interaction energy between gas components and sulfur molecules. These findings hold important implications for sulfur control and treatment in high-H2S gas reservoirs.