硫化氢形成与C2＋气态烷烃形成的同步性研究--几个模拟实验的启示

The Generation Synchroneity of H2S and C_(2+) Gaseous Alkane——Implications of Some Simulation Experiments

硫酸盐热还原(TSR)是高含硫天然气形成的主要原因,但是参与TSR反应的主要烃类组分仍存在争议。在对比分析湿气—硫酸镁反应体系、甲烷—硫酸钙反应体系以及重烃—硫酸镁反应体系模拟实验的基础上,通过对TSR化学反应表达式的分析以及化学动力学、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,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+气态烷烃的增加而加快,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。根据油气生成演化阶段分析,认为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,如果构造环境发生改变就会进一步调整成藏。因此,天然气中硫化氢含量不仅受生成条件控制,还受运移通道、保存条件等因素控制。

The thermochemical sulphate reduction （TSR） is believed to be the determinative factor for gas reservoirs to generate high content of H2S （ the volume percent of H2S above 5% ）, but the main hydrocarbon compounds react with sulphate are still not distinctly made sure. In this paper, based on the contrast analysis of TSR reaction systems （ wet gas and magnesium sulfate, methane and calcium sulphate, heavy hydrocarbon and magnesium sulfate）, through the analysis of TSR chemical equations and study of chemical kinetics and chemical thermodynamics, combined with geologic information, it is concluded that methane is believed to be the product of the TSR reaction between heavy hydrocarbon and sulphate, and not main reactant; there is synchroneity between the TSR reaction and the increasing of C2＋ gaseous Alkane, the TSR reaction rate increase as C2＋ Gaseous Alkane increase and the volume of H2S almost not increase till the wet gas cracked to be dry gas and then dry gas with H2S is generated. According to the analysis of oil and gas evolution stage, it is believed that TSR mainly at the stage of condensate gas generation by thermal cracking. When crude oil being cracked to be natural gas with H2S, the pressure system is changed and gas with H2S will be newly accumulated and the natural gas with H2S will be accumulated again in new traps if the structural environment changes. So, the volume of H2S in controlled by generation conditions but by other factors, such as migration pathway and preservation conditions. natural gas reservoirs is not only conditions, reservoirs conditions.