四川盆地是中国高含硫化氢天然气分布最集中的地区,目前已在震旦系(威远气田)、下三叠统飞仙关组(罗家寨、普光、渡口河、铁山坡、七里北)、嘉陵江组(卧龙河)和中三叠统雷口坡组(磨溪、中坝)发现了近10个高含硫化氢的大中型气田(藏),探明储量5000×10^8m^3。这些高含硫化氢气藏普遍经历过较大的埋深过程(储层经历过较高温度),储层上下或储层中间均发育有膏质岩类,且气源充足,具备硫酸盐热化学还原反应(Thermochemical Sulfate Reduction,TSR)发生的物质基础和热动力条件。从气藏地质特征以及天然气组成和碳、硫同位素等方面的证据表明,四川盆地中、下三叠统和震旦系气藏的硫化氢属于TSR成因。而且TSR对烃类的大量选择性消耗一方面导致天然气干燥系数增大,另一方面导致气藏充满度降低,气藏压力系数变小。
The Sichuan Basin is the richest area in high H2S-bearing natural gas in China. Presently, explored reserves of over 500 billion cubic meter of natural gas have been found, which lie in Sinian (Weiyuan gas field), the Feixianguan Formation of Lower Triassic (Luojiazhai, Puguang, Dukouhe, Tieshanpo and Qilibei gas fields), Jialingjiang Formation of Lower Triassic (Wolonghe gas field) and Leikoupo Formation of Middle Triassic (Moxi and Zhongba gas fields), including about 10 large and medium gas fields (pools) with high H2S content. All the gas pools are buried in great depth (reservoir suffered high temperature), and the upper, lower or middle reservoirs have gypsiferous rock and sufficient hydrocarbon gas, so, the reservoirs possess material and dynamic conditions of thermochemical sulfate reduction (TSR). The geology of gas pools, natural gas components, carbon and sulfur isotopes indicate that the H2S of Middle and Lower Triassic and Sinian gas pools are of TSR origin. Selective hydrocarbon depletion makes natural gas drier, and correspondingly the gas pool filling and pressure coefficient decrease.