川东北高含硫天然气形成机理

Generation mechanismof acid gas in Northeast Sichuan

马喜斌 张建勇 张燕 陈东 谢建瓴 李小蓉

中原油田分公司采油四厂，河南 濮阳 457073 中国科学院地质与地球物理研究所，甘肃 兰州 73000 中原油田分公司技术安全监督处， 河南 濮阳 457001

川东北高含硫天然气中的硫化氢来自硫酸盐热还原（TSR）反应，但高含硫天然气的分布与硫酸盐的分布并不完全一致，与地层水中SO42-离子浓度分布也不一致。在对比分析湿气-硫酸镁反应体系、甲烷-硫酸钙反应体系及重烃—硫酸镁反应体系模拟实验的基础上，通过TSR化学反应表达式的分析及化学动力学、热力学等理论的探讨，结合实际地质资料，认为甲烷是C2+烃类参与TSR反应的产物而不是反应物，TSR的发生与C2+气态烷烃的产生具有同步性，TSR的反应速率随着C2+气态烷烃的增加而增加，当湿气裂解为干气后，硫化氢含量几乎不再增加，从而形成干气伴生硫化氢。川东北地区TSR主要发生在热裂解生凝析气阶段，原油裂解为硫化氢伴生天然气后，压力系统发生改变，天然气重新聚集成藏，喜山期构造运动而进一步调整成藏，因此现今高含硫天然气藏分布规律极其复杂。

The hydrogen sulphide of acid gas is generated by the thermal reduction reaction of sulphate in Northeast Sichuan. But the
acid gas distribution is not completely accordant with the distribution of sulphate and SO42- ionic concentration. Thermal reduction
reaction of sulphate is believed to be the determinative factor for gas reservoirs to generate high sulphur content. Based on the
contrast and analysis of the wet gas and magnesium sulfate, methane and calcium sulphate, heavy hydrocarbon and magnesium
sulfate, it is concluded that the methane is the product rather than the reactant of the thermal reduction reaction of sulphate the C2+
hydtocarbons affiliated in terms of the data analysis. The hydrogen sulphide content scarcely increases when the wet gas is cracked
to be the dry gas, which the dry gas with hydrogen sulphide is generated. The thermal reduction reaction of sulphate is mainly at the
stage of condensate gas generation by thermal cracking in Northeast Sichuan. When the crude oil is cracked to be natural gas with
hydrogen sulphide, the pressure system is changed and the natural gas has been accumulated again in new traps.