准噶尔盆地石炭系与二叠系主力烃源岩地球化学特征对比研究

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，C_29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。

Comparisons of Geochemical Characteristics of Carboniferous and Permian Main Source Rocks in Junggar Basin

Analysis and comparison of the biomarkers and compound-specific stable carbon isotope of n-alkenes were mainly conducted for Carboniferous and Permian source rocks from Junggar Basin,NW China.The organic matter abundance of Carboniferous and Permian source rocks is relatively high and the maturity of them is high in the northwestern and southern edges while low in the eastern region of the basin,and all of them match the requirements of the hydrocarbon generation.The Carboniferous source rocks in the northwestern and eastern regions are characterized by high Pr/Ph ratios and C_29sterane,and low gammacerane and C₂₈ sterane,which imply the freshwater lacustrine depositional environment of the source rocks dominated by type Ⅲ organic matter.Permian source rocks were deposited in the brackish water-salt water lacustrine environment and dominated by type Ⅰ and type Ⅱ organic matter.They had low Pr/Ph ratios,a certain amount of beta-carotane and relatively high content of gammacerane.Their content ofC₂₈ sterane is apparently higher than that of Carboniferous.The Carboniferous source rocks are characterized by type Ⅲ organic matter and heavy carbon isotope of kerogen.However,the compound-specific stable carbon isotope of their n-alkanes differs apparently because of the influence of their organic sources and maturity.As for Permian source rocks,the good correlation exists in the compound-specific stable carbon isotope of n-alkanes and kerogens.The compound-specific stable carbon isotope of alkanes is relatively high for those from Type Ⅲ organic matter and relatively low for those from type Ⅱ and type I organic matter.Additionally, the Permian source rock in the south margin has some input of methane bacteria parent matter and has relatively low carbon isotopes of the kerogen,n-alkanes and some hopane compounds.