准噶尔盆地烷烃气碳同位素组成及来源

通过对全盆地烷烃气碳同位素组成进行分析，明确了准噶尔盆地烷烃气成因类型、来源及分布。准噶尔盆地天然气主要包括成熟—过成熟油型气、成熟—过成熟煤型气、过渡气和生物气等。准噶尔盆地烷烃气碳同位素倒转普遍，碳同位素倒转原因包括细菌氧化作用、油型气和煤型气混合、不同源煤型气混合以及同源不同阶煤型气混合。准噶尔盆地煤型气包括3类：①煤型气重烃气碳同位素组成较重(δ¹³C₂＞-26.0‰)，主要为成熟—高成熟，来源于侏罗系烃源岩；②煤型气重烃气碳同位素组成相对较轻(δ¹³C₂＜-26.0‰)，成熟度范围广，来源于侏罗系、二叠系乌尔禾组和佳木河组烃源岩中的一套或多套；③煤型气重烃气碳同位素组成分布范围广，主要为高—过成熟，来源于石炭系烃源岩。

Carbon isotopic composition and source of hydrocarbon gases in the Junggar Basin

The genetic style,source rock and distribution of hydrocarbon gases in the Junggar Basin were determined through the carbon isotopic compositions analyses.Mature to post mature oil-type gas,mature to post mature coal-type gas,transition gas and biogas are identified in the Junggar Basin.Partly reversed order of carbon isotopic compositions of hydrocarbon gases in the Junggar Basin are attributed to one or several of the following reasons:Mixing of oil-type and coal-type gases,mixing of coal-type gases of different sources,mixing of coal-type gases of varied maturity,and bacterial oxidation.Three types of coal-type gases in the Junggar Basin are identified.The first type of coal-type gases characterized by high δ13C value of heavy hydrocarbon gases (δ13C2>-26.0‰),are mature to high mature and generated from Jurassic source rocks.The second type of coal-type gases characterized by low δ13C value of heavy hydrocarbon gases (δ13C2<26.0‰) and wide maturity range,generated from one or several source rocks in the Jurassic and the Wuerhe Formation and Jiamuhe Formation of Permian.The third type characterized by δ13C value of heavy hydrocarbon gases and the high-post maturity,generated from the Carboniferous source rocks.