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重点对准噶尔盆地石炭系与二叠系主力烃源岩生物标志化合物分布特征,及单体烃碳同位素特征进行分析与对比。该盆地石炭系和二叠系烃源岩有机质丰度都相对较高,成熟度以西北缘与南缘较高,准东较低,各项参数均达到了烃源岩要求。盆地石炭系烃源岩生物标志化合物特征具有Pr/Ph值较高,伽马蜡烷含量低,C29甾烷含量较高,而C28甾烷含量较低的特点,生物标志化合物特征反映出石炭系烃源岩,形成环境为淡水湖湘,主要为Ⅲ型有机质。二叠系烃源岩Pr/Ph值整体较低,伽马蜡烷指数相对较高,且含有一定量的β-胡萝卜烷,C28甾烷明显高于石炭系烃源岩,沉积环境主要为半咸水—咸水盐湖相,有机质类型为Ⅰ型、Ⅱ型。石炭系烃源岩有机质类型主要为Ⅲ型,其干酪根碳同位素组成较重,但单体烃碳同位素差别较大,母质来源和成熟度都影响着正构烷烃单体烃碳同位素的分布。二叠系烃源岩干酪根分布特征表明主要源岩有机质类型为Ⅲ型、Ⅱ型和Ⅰ型,其正构烷烃单体烃碳同位素的分布特征与干酪根碳同位素分布有较好的相关性,Ⅲ型有机质单体烃碳同位素组成较重,而Ⅱ型和Ⅰ型有机质单体烃同位素组成较轻;南缘二叠系烃源岩有明显的甲烷菌母质输入现象,干酪根、单体烃碳同位素组成和一些藿类化合物碳同位素组成都表现为较轻的特点。
The distribution characteristics of biomarkers of Carboniferous and Permian main source rocks in the Junggar Basin and the characteristics of carbon isotope of single hydrocarbon are analyzed and compared. The organic carbon abundances of Carboniferous and Permian source rocks are relatively high in this basin. The maturity is higher in the northwestern and southern margins and lower in the quasi-east, and all the parameters reach the requirements of source rock. The characteristics of biomarkers of Carboniferous hydrocarbon source rocks in the basin are characterized by higher Pr / Ph value, lower gamma-alkane content, higher content of C29 sterane, and lower content of C28 sterane. The characteristics of biomarker compounds reflect the characteristics of Carboniferous Source rock, the formation of freshwater lake Hunan, mainly Ⅲ organic matter. The Pr / Ph value of Permian hydrocarbon source rock is relatively low with a relatively high Gamma-C-Alkane index and a certain amount of β-Carotenoid, which is significantly higher than that of Carboniferous hydrocarbon source rocks. The sedimentary environment is mainly half Saltwater-saltwater salt lake, organic matter types are type I and type II. Carboniferous source rocks are mainly of type III, with a relatively high carbon isotopic composition of kerogen but a large difference in carbon isotope of monomer hydrocarbon. Both parent source and maturity influence the distribution of carbon isotopes of n-alkanes. The distribution characteristics of kerogen in Permian source rocks indicate that the organic matter types of the main source rocks are type Ⅲ, type Ⅱ and type Ⅰ. The distribution characteristics of hydrocarbon carbon isotopes of n-alkanes have a good correlation with the distribution of carbon isotopes of kerogen , The type Ⅲ organic carbons had a heavier carbon isotope composition, while the type Ⅱ and type Ⅰ organic hydrocarbons had lighter hydrocarbon isotope compositions. The Permian source rocks in the southern margin had obvious methanemethanoidal input, and kerogen, monomer The carbon isotopic compositions of hydrocarbons and some carbon isotope compositions of these compounds show a lighter trait.