Geochemical Characteristics and Origin of Natural Gas in East Portion of Tarim Basin(II)
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摘要: 天然气的组分和碳、氢同位素组成特征研究表明塔里木盆地已发现的天然气均为热解气。通过气源对比可知,该盆地东部地区的天然气主要有两种类型 :1)是来自震旦纪到下古生界海相腐泥型母质的油型气,其甲烷、乙烷、丙烷δ13C值,分别为-44.5‰~-33.8‰、- 42‰~-2 8.1‰和-35.4‰~-2 8.4‰,其甲烷的氢同位素组成大于- 2 0 0‰;2 )是产自中生代陆相腐殖型源岩的煤型气,其甲烷、乙烷、丙烷的δ13C值分别为-40.5‰~-33.1‰、- 2 9.7‰~-2 1.3‰和-2 6.3‰~-2 0.3‰,其甲烷的氢同位素组成小于-2 0 0‰。将天然气的地化特征与地质背景相结合判断可知,在塔北隆起地区一些天然气藏是由成熟 (高成熟 )阶段的油型气与过成熟阶段的油型气混合形成,另一些天然气藏是由成熟阶段的油型气和成熟阶段的煤型气混合形成.Abstract: Research on chemical components and isotope composition of carbon and hydrogen of natural gases from the Tarim basin shows that all discovered gases in this basin are thermogenic.With respect to source organic matter there are two types of gases: 1)the oil-type gas, which generated from Sinian to lower Palaeozoic marine source rocks with the sapropelic organis matter with-44.5%。-33.8%0 of δ13C1,,-42.0%。-28.1%c of δ13C2,-35.4%。-28. 4%0 of δ13C3, and heavier than- 200%0 of δD1;2) the coal-type gas, which generated from Mesozoic terrestrial source rocks with the humic organic matter with-40.5%‘-33.1%0 of δ13C1,-29.7%。-21.3%c of δ13C2,-26.3%。-20.3%c of δ13C1,and lighter than-200%0 of δD1. Based on the geochemical characters and geological setting Tahei uplift region is regarded as having some reservoired gas pools formed by mixed mature oil-type gas with post matured oil-type gas.Some reservoired gas pools are formed by mixed mature oil-type gas with mature coal-type gas.
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Key words:
- Tarim basin /
- natural gas /
- carbon isotopic composition /
- hydrogen isotopic composition
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