川东北飞仙关组高含H2S气藏特征与TSR对烃类的消耗作用

四川盆地川东北地区飞仙关组近年来发现了罗家寨、渡口河、铁山坡、普光等多个大、中型气田，它们均以高含硫化氢（H2S在气体组分中占10%~17%，平均为14%）为最显著特征。深入研究后发现，虽然这些大型鲕滩气藏储量规模较大，单井产量高；但是这些气藏充满度普遍偏低（在25%~91%之间），压力系数不高（大部分小于1.2）。从成藏条件来看，该区鲕粒溶蚀孔隙发育，有效储层厚度大，二叠系龙潭组、志留系龙马溪组优质烃源岩十分发育，油气源充沛，而且由断层构成的疏导体系发育，泥岩及膏质岩类组成的盖层封盖性良好，因此气藏的低充满度现象，可能是圈闭中发生过大量烃类的损耗或消耗。由于川东北飞仙关组H2S是烃类和硫酸盐在储层中发生热化学反应（TSR）形成的，气藏中硫化氢含量与压力系数、地层水矿化度、烃类含量等都存在反相关关系，因此飞仙关组高含硫化氢气藏压力系数小、充满度低，很可能是烃类被TSR大量消耗和储集空间增容所致。

Characteristics of Gas Reservoirs with High Content of H2S in the Northeastern Sichuan Basin and the Consumption of Hydrocarbons due to TSR

During the recent years, several medium and large-scale gas fields, such as the Luojiazhai, Dukouhe, Tianshanpo and Puguang, etc, whose most remarkable features being the higher H_2 S contents, have been discovered in the northeastern Sichuan basin. Their H_2 S contents among the gas compositions account for 10 to 17 percent while the average being 14 percent. Based on the thorough study, it can be found that although these large-scale oolitic shoal gas reservoirs usually have rich reserves along with high individual-well producing rate, their coefficients of fullness, which ranging from 25 to 91 percent, are generally rather low, also, their pressure coefficients are not high and mostly less than 1.2. According to their reservoir forming conditions, i.e., the abundant oolitic dissolution pores, the efficient reservoirs with huge thickness, the robust gas source, the well-developed transport systems, together with the excellent seal ability of the caprocks constituted by shale and gypsolyte, their lower coefficients of fullness were possibly due to a large quantity of hydrocarbons had been consumed or depleted within the traps. In the northeastern Sichuan basin, due to the H_ 2 S contained within the Feixianguan formation was generated from the TSR reactions, which occurred within reservoirs, between hydrocarbons and sulfate, there exist negative correlations between the H_ 2 S contents and the pressure coefficients, the reservoir water salinity together with the hydrocarbons contents, etc. Therefore, as far as the gas reservoirs with high H_2 S contents of the Feixianguan formation was concerned, their lower pressure coefficients and coefficients of fullness are likely caused by both the hydrocarbons had been consumed greatly due to TSR and the volume of reservoirs had been expanded.