库车坳陷克拉苏冲断带轻质原油地球化学特征及成因

Geochemical Characteristics and Genesis of Light Oil in Kelasu Thrust Belt of Kuqa Depression

库车坳陷克拉苏冲断带以产气为主,并伴生一定量的轻质油。基于库车坳陷克拉苏冲断带18个轻质原油样品有机地球化学分析,总结了轻质原油生物标志化合物特征,对轻质原油进行了成因分类,并确定了其母质来源。研究结果表明,克拉苏冲断带克拉、大宛和大北地区轻质原油具有低Pr/Ph比值、高伽马蜡烷含量的特征,具有明显的湖相烃源岩特征。克拉地区原油母质以藻类输入为主,沉积于还原咸化环境。大宛和大北地区原油母质以高等植物输入为主,沉积于弱还原咸化环境。在克拉和大北地区部分原油母质还存在混合来源特征。按照生物标志化合物特征可以将库车坳陷克拉苏冲断带轻质原油划分为3种类型:第一类原油主要分布在大宛和大北地区,推测主要来源于中侏罗统恰克马克组下段湖相泥岩;第2类原油分布在克拉地区,推测主要来源于三叠系湖相烃源岩;第3类原油分布在克拉和大北地区,推测主要来源于三叠系湖相烃源岩,但侏罗系煤系烃源岩也具有一定贡献。

Kelasu thrust belt of Kuqa Depression is dominated by generating gas associated with a certain amount of light oil.Based on organic geochemical analysis of 18 light crude oil samples in Kelasu thrust belt of the Kuqa Depression,this study summarized the characteristics of biomarkers compound of light oil and determined genetic classification and the organic sources.The results show that light oil from Kela,Dawan and Dabei areas of Kelasu thrust belt is mainly from lacustrine source rocks of Kuqa Depression provides low Pr/Ph and high content of gammacerane.Organic matter of oil sources are mainly derived from algae deposited in salty environment in Kela area.while organic matter of oil sources in Dawan and Dabei areas are mainly derived from terrestrial higher plant,deposited in weakly salty environment.Organic matter of some oil sources in Kela and Dabei areas are both contributed by algae and higher plants.According to biomarker compounds features,light oils are classified into three types in Kelasu thrust belt of Kuqa Depression.The first type of light oil is mainly found in Dawan and Dabei areas,presumably mainly from lacustrine mudstones of lower section in Jurassic Qiakemake Formation.The second type of light oils is located in Kela area,presumably mainly from the Triassic lacustrine source rocks.The third type of some light oils developed in Kela and Dabei areas,presumably mainly from the Triassic lacustrine source rock,but the Jurassic coal series also have minor contribution.