摘要
四川盆地天然气绝大部分含有硫化氢,部分含量高达15%以上。其中高含硫化氢天然气主要分布在三叠系飞仙关组、雷口坡组和嘉陵江组;震旦系、石炭系、二叠系属于低含硫化氢,上三叠统须家河组和侏罗系属于微含硫化氢或不含硫化氢天然气藏。研究表明,三叠系飞仙关组、雷口坡组和嘉陵江组、震旦系、石炭系储层中发育的膏质岩类为TSR形成硫化氢提供了物质基础;富含有机硫源岩的高温裂解是二叠系低含硫化氢天然气的主要成因。硫同位素组成表明,高含硫化氢天然气的硫同位素比储层硫酸盐硫同位素δ34S亏损7‰～11‰;而低含硫化氢天然气硫同位素分布区间较宽,在0‰～20‰之间,大部分比同期硫酸盐的硫同位素轻15‰左右。四川盆地三叠系膏岩的硫同位素值分布较宽,并呈现阶梯状变化,而硫化氢的硫同位素则呈现出相似的分布规律,表明各气层硫化氢中的硫来自于本层系的硫酸盐,即TSR发生在各自的储集层中;另外四川盆地三叠系TSR发生时各气藏的温度条件相近,即各气藏的硫化氢在大致相同的温度条件下发生;同时也说明TSR过程中硫同位素的分馏过程与硫酸盐本身硫同位素数值的高低无关,而与TSR反应的温度条件和反应程度有关。还建立了运用硫化氢的硫同位素和含量判识硫化氢成因类型的模式。
The natural gases in Sichuan basin commonly contain H2S from minim to 18.6% in content. The natural gases with high content of H2S occur in Feixianguan Formation, Leikoupo Formation and Jialingjiang Formation of Triassic, the Sinian, Carboniferous and Permian reservoirs have lower H2S contents, and Triassic Xujiahe Formation and Jurassic contain trace amount or no H2S in natural gas reservoirs. The research shows that the gypsiferous rocks of Feixianguan Formation, Leikoupo Formation and Jialingjiang Formation of Triassic, Sinian and Carboniferous reservoirs provide the material basis for the formation of H2S by thermochemical sulfate reduction （TSR）, and the Permian natural gases with low content of H2S are mainly from the pyrolysis of organic sulfur source rock. The stable sulfur isotopic compositions show that the gases with high content of H2S have a δ^34S depletion of 7‰- 11‰relative to the reservoirs sulfate, and the 334S of the gases with low content of H2S have a wide range （0‰-20‰） and are about 15‰lighter than that of the contemporary sulfates. The sulfur isotope values of the Triassic gypsiferous rocks in Sichuan basin have a wide distribution extent and show stepwise changes, which are similar to those of H2S, indicating that the sulfur in H2S came from the sulfate and TSR occurred in the respective reservoirs. Otherwise, the temperature conditions are similar as the TSR occurred, which means that the H2S generates in the similar temperature conditions and the fractional process of sulfur isotopes have no concern with the sulfur isotope values of sulfate, and the temperature and extent of reaction are the key factors in the TSR process. The pattern for identifying the H2S genetic types is developed by using the stable sulfur isotope values and contents of H2S.
出处
《地球化学》
CAS
CSCD
北大核心
2006年第4期432-442,共11页
Geochimica
基金
中国石油天然气股份有限公司科技项目(040502-10-01)
国家重点基础研究发展计划项目(2001CB209100)
