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厘清济阳坳陷三合村洼陷浅层天然气成因.通过采集浅层天然气及伴生原油样品,在进行天然气组分、碳、氢同位素组成以及伴生原油饱和烃色谱分析的基础上对浅层天然气的成因进行了研究,认为三合村洼陷浅层天然气主要来自微生物对原油的降解,属于典型的次生生物气,微生物还原二氧化碳生成甲烷是次生生物甲烷的主要生成途径.研究结果表明:天然气组分以甲烷为主,干燥系数大(C_/C_1~+>0.931);甲烷碳同位素比值变化大(-50.03‰<δ~(13)C_1<-39.03‰),并与甲烷氢同位素比值呈负相关关系;重烃组分含量低且碳同位素比值普遍较大(-33.62‰<δ~(13)C_2<-19.72‰,-29.27‰<δ~(13)C_3<-7.64‰,-26.28‰<δ~(13)n-C_4<-15.63‰);二氧化碳碳同位素比值表现为异常的正值(2.82‰<δ~(13)CCO_2<17.69‰).微生物对湿气组分的选择性降解以及次生生物甲烷的生成是导致济阳坳陷三合村洼陷天然气组分、同位素组成复杂特征的主要原因.浅层天然气成因的确定对后续勘探浅层气藏附近的降解型稠油油藏具有重要的指示意义.
Clarifies the origin of shallow natural gas in Sanhe village depression of Jiyang Depression.Based on the analysis of gas component, carbon and hydrogen isotope compositions and the chromatographic analysis of the associated crude oil saturated gas by collecting the samples of shallow natural gas and associated crude oil, It is considered that the shallow natural gas in Sanhe village depression mainly comes from the degradation of crude oil by microorganisms and belongs to the typical secondary biogas.The generation of methane by microbial reduction of carbon dioxide is the main generation pathway of secondary methane.The results show that: The main component of natural gas is methane, with a large coefficient of dryness (C_ / C_1 ~ + 0.931); the carbon isotope ratio of methane varies greatly (-50.03 ‰ <δ ~ (13) C_1 <-39.03 ‰) (-33.62 ‰ <δ ~ (13) C_2 <-19.72 ‰, - 29.27 ‰ <δ ~ (13) C_3) <-7.64 ‰, and the carbon isotope ratios were relatively low 26.28 ‰ <δ ~ (13) n-C_4 <-15.63 ‰), and the carbon isotope ratio of carbon dioxide showed an abnormal positive value (2.82 ‰ <δ ~ (13) CCO_2 <17.69 ‰) Sexual degradation and the formation of secondary methane are the components of natural gas in Sanhe village depression in Jiyang depression, Isotopic composition of the main causes of complex features.Determination of shallow gas genesis of the subsequent exploration of shallow reservoirs near the degradation of heavy oil reservoirs is an important indicator.