Abstract To understand the isotope fractionation of methane (CH4) during thermochemical sulfate reduction (TSR), isothermal pyrolysis of CH4/N2 gas involving gypsum + MgCl2 and MgSO4 solutions were conducted in a gold-tube system. CH4 was oxidized to generate H2S and CO2 via TSR in the hydrothermal experiments with sulfate. The δ13C1 becomes more enriched with the conversion of CH4. However, there is no evident enrichment of 2H for CH4 during TSR under hydrothermal conditions. Ab initio quantum calculations based on Density Functional Theory (DFT) demonstrate that the kinetic isotope effect (KIE) rather than the thermodynamic equilibrium isotope effect (EIE) governs the 13C fractionation during methane TSR. The kinetic 13C fractionation factor (α) for TSR of CH4 involving SO42− and HSO4− is 0.960–0.992 between 0 °C and 600 °C. Combining these experimental results, α for methane TSR was in the range 0.98–0.99 with an average value of 0.985. Based on these results, the extent of methane TSR for natural gas in the Puguang gas field in the northeastern Sichuan Basin was determined via the evolution of δ13C1. Geological extrapolation of the kinetic parameters and KIE suggests that the conversion of CH4 via TSR in the P2ch-T1f Formations in this gas field is

中文翻译：

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涉及甲烷和硫酸盐的水热实验：深入了解热化学硫酸盐还原过程中甲烷的碳同位素分馏

摘要 为了了解硫酸盐热化学还原 (TSR) 过程中甲烷 (CH4) 的同位素分馏，在金管系统中进行了涉及石膏 + MgCl2 和 MgSO4 溶液的 CH4/N2 气体等温热解。在硫酸盐的水热实验中，CH4 通过 TSR 被氧化生成 H2S 和 CO2。随着 CH4 的转化，δ13C1 变得更加丰富。然而，在热液条件下的 TSR 过程中，CH4 没有明显的 2H 富集。基于密度泛函理论 (DFT) 的从头算量子计算表明，在甲烷 TSR 期间，动力学同位素效应 (KIE) 而非热力学平衡同位素效应 (EIE) 控制着 13C 分馏。涉及 SO42− 和 HSO4− 的 CH4 TSR 的动力学 13C 分馏因子 (α) 在 0 °C 和 600 °C 之间为 0.960–0.992。结合这些实验结果，甲烷 TSR 的 α 在 0.98-0.99 的范围内，平均值为 0.985。基于这些结果，通过δ13C1的演化确定了川东北普光气田天然气甲烷TSR的程度。动力学参数和 KIE 的地质推断表明，该气田 P2ch-T1f 地层中 CH4 通过 TSR 的转化是