四川盆地含硫化氢气藏分布特征及硫化氢成因探讨

Distribution Characteristics of Hydrogen Sulphide-bearing Gas Pools and the Genesis of Hydrogen Sulphide in Sichuan Basin

目前,四川盆地是我国发现含硫化氢气藏数目最多、储量最大的含油气盆地。该盆地产硫化氢的层位众多,从老到新分别有震旦系、石炭系、二叠系及三叠系等。平面上,川东气区硫化氢含量最高,其次为川西气区和川中油气区,川南气区硫化氢含量最低。纵向上,不同层位的含硫化氢气藏内硫化氢的含量存在较大差异。三叠系飞仙关组硫化氢含量最高,其次为二叠系长兴组和三叠系雷口坡组,二叠系茅口组气藏中硫化氢的含量最低。震旦系灯影组和石炭系黄龙组硫化氢含量比较稳定。嘉陵江组气藏中不同层段的硫化氢含量差别较大,其中嘉五段和嘉四段硫化氢含量最高。通过沉积相、埋藏史、热史、包裹体均一温度、硫同位素以及天然气组分等的分析,认为川东气区飞仙关组和长兴组高硫化氢型气藏、川东气区和川南气区的嘉陵江组气藏(除了嘉一段)、川南气区威远震旦系灯影组气藏、川西气区中坝气田雷口坡组气藏以及川中油气区磨溪气田雷口坡组气藏中的硫化氢为硫酸盐热还原反应(TSR)成因;川东气区石炭系黄龙组气藏和川南气区二叠系茅口组气藏硫化氢为含硫有机质热解成因。

At present,Sichuan basin is a petroliferous basin which has the biggest number of H2S-bearing gas reservoirs and of which the H2S-bearing gas reserves is also the biggest in China.Reservoirs producing H2S-bearing natural gas are distributed in Sinian,Carboniferous,Permian,and Triassic.Transversely,the East Gas District（EGD） has the highest content of H2S,followed by the West Gas District（WGD） and the Middle Oil-Gas District（MOGD）,and the South Gas District（SGD） has the least.Vertically,the content of H2S is various among the different reservoirs and even in different members of the same strata or well.The H2S content of natural gas in Triassic Feixianguan Formation is the highest,followed by those in the Permian Changxing Formation and in the Triassic Leikoupo Formation,and that in the Permian Maokou Formation is the least.The differences of the H2S content among different wells in the Sinian Dengying Formation are slight,and the similar phenomenon also exists in Carboniferous Huanglong Formation.Significant H2S content differences have been observed in the natural gas from different members of Jialingjiang Formation,in which the gas from the fifth and the forth members have the highest H2S content.According to the comprehensive analysis of the sedimentary facies,burial history,thermal history,homogenization temperature of the fluid inclusions,as well as the sulfur isotope ratios and the components of the natural gas,it can be concluded that the H2S of the Feixianguan Formation and the Changxing Formation in EGD,the Jialingjiang Formation（except the first member） in EGD and SGD,the Dengying Formation gas pool of Weiyuan gas reservoir in SGD,the Leikoupo Formation gas pool of Zhongba gas reservoir in WGD and the Leikoupo Formation gas pool of the Moxi gas reservoir in MOGD were generated by the thermochemical sulfate reduction（TSR）,while that in the Huanglong Formation in EGD and the Maokou Formation in SGD were generated by the cracking of the organic matter（kerogen or oil） which contains sulfur.