Molecular insights into the interfacial tension of liquid sulfur with formation water/natural Gas: Effects of temperature, pressure, and composition

Z Li and DQ Zeng and T Li and Q Li and R Zhang and L Huang and XG Wang and H Wang, GAS SCIENCE AND ENGINEERING, 139, 205633 (2025).

DOI: 10.1016/j.jgsce.2025.205633

The exploitation of natural gas with high H2S content may lead to the precipitation of dissolved sulfur. This process can negatively impact clean and sustainable production. The lack of reliable interfacial tension (IFT) data between liquid sulfur and formation water/natural gas makes it difficult to use numerical simulations for optimizing production strategies. This study develops and validates molecular models for liquid sulfur, natural gas, and formation water. These models accurately reproduce density, viscosity, and surface tension. Using molecular dynamics simulations, we calculate the IFTs between liquid sulfur and formation water/natural gas. We also investigate the effects of temperature (395-425 K), pressure (1-30 MPa), salinity (5000-200000 mg/L), ion type, and gas composition. The results demonstrate that liquid sulfur-formation water IFT > liquid sulfur surface tension > liquid sulfur-natural gas IFT. Increasing temperature and pressure decrease the IFTs, while ions significantly increase them. Liquid sulfur-brine IFTs follow the order: MgCl2 > CaCl2 > Na2SO4 > NaHCO3. This is consistent with the strengths of ion-water interactions. H2S and CO2 significantly reduce the liquid sulfur-natural gas IFT, with H2S exerting a more pronounced effect. When CO2 and H2S coexist, H2S's IFT- reducing capacity is weakened due to competitive adsorption. This research provides critical parametric inputs for numerical simulations to control sulfur precipitation and enhance recovery in high-H2S gas reservoirs.

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