煤成天然气碳氢同位素组成及成藏意义:以鄂尔多斯盆地上古生界为例  

Carbon and hydrogen isotopic compositions of coal-genetic natural gases and their applications in accumulation in Upper Paleozoic,Ordos Basin

作　　者：冯乔[1,2] 耿安松[3] 廖泽文[3] 张小莉[4] 

机构地区：[1]山东科技大学地球信息科学与工程学院 [2]中国科学院广州地球化学研究所有机地球化学国家重点实验室,广东广州510640 [3]中国科学院广州地球化学研究所有机地球化学国家重点实验室 [4]西北大学地质学系大陆动力学重点实验室

出　　处：《地球化学》2007年第3期261-266,共6页Geochimica

基　　金：国家重点基础研究发展计划项目(2003CB214603);国家"十五"科技攻关计划项目(2001BA605A-04)

摘　　要：天然气碳氢同位素在线分析表明鄂尔多斯盆地上古生界天然气属于煤成气,不同地区不同层位的天然气碳氢同位素组成存在明显差异,构成了3类不同的分布模式,即榆林型(C2—P2)、苏里格型(P1—P2)和神木-米脂型(P3)。榆林型天然气碳氢同位素组成符合随碳数增加δ13C与δD值均逐渐变重的热成因气的变化规律,为成熟—较高成熟阶段的产物;苏里格型天然气C3H8的δ13C3与δDC3值均出现比C2H6偏轻的特征,可能是煤岩生烃过程中,同位素动力学分馏效应固有特征的反映;神米型的突出特点是石千峰组天然气的碳氢同位素值明显比其下伏气藏偏轻,δ13C1、δ13C2偏轻约2.5‰,δDC1值偏轻约12‰(榆17井),可能为较高热演化阶段凝析油裂解和(或)运移分馏聚集而成。这3类气藏碳氢同位素组成的差异,反映了不同热演化阶段煤成天然气同位素组成的固有特征,从而为天然气聚集与成藏研究提供了重要例证。The on-line analysis of natural gases from the Upper Paleozoic reservoir indicated that they were derived from coal measures. There are distinct differences in isotopic compositions of the natural gases from different areas and different horizons. And three distribution patterns are found： Yulin （C2- P2）, Sulige （P1 -P2） and Shenmu- Mizhi （P3）. The carbon and hydrogen isotopic compositions of natural gases of Yulin pattern have the law of the thermogenic gas that the δ^13C and δD values would increase gradually with increasing carbon numbers. They were produced during the high maturation stage. The δ^13C3 and δDc3 values of propane （C3H8） of Sulige pattern were heavier than those of ethane （C2H6）, which was the intrinsic characteristic of the isotope dynamic fractionation. The carbon and hydrogen isotopic values of natural gases of Shenmi pattern are lower in Shiqianfeng Formation than those in the underlying horizon. For example, the δ^13C1 and δ^13C2 values in Shiqianfeng Formation was 2.5‰ lower, and δDc, was 12‰ lower than those in the underlying horizon in well Yu17. They could be produced based on the cracking of condensate and the fraetionation of migration and accumulation during the high maturation stage. These patterns are a good example of migration and accumulation of natural gases based on the difference of the isotopic compositions at the different thermal stage.

关 键 词：碳氢同位素 分布模式 天然气成藏 鄂尔多斯盆地 

分 类 号：P593[天文地球—地球化学]