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塔里木盆地乌什凹陷乌参1井、神木1井和神木2井的相继突破,揭示了该区具有广阔的油气勘探前景。通过饱和烃和轻烃气相色谱对乌什凹陷原油地球化学特征进行了全面的分析,并与塔里木盆地典型的陆相原油和湖(海)相原油进行了对比。神木2井和乌参1井原油Pr/Ph值分别为2.35和3.53,表现出典型的煤成烃特征。乌什凹陷原油具有相对较高的芳烃(苯和甲苯)、甲基环己烷和环己烷含量,而环戊烷和无环烃类相对含量较低,说明陆源有机质贡献较大。乌什凹陷原油庚烷指数介于25.0%~27.6%之间,异庚烷指数介于2.5%~2.7%之间,处在高成熟早期阶段。乌什凹陷原油未经历水洗和生物降解作用,但发生了较为明显的蒸发分馏作用,导致轻烃组分中芳烃含量增加,而正构烷烃含量减少。通过OCSD—C7轻烃星状图和C7轻烃系统三角图分析,乌什凹陷原油和迪那2气田凝析油同属于陆相原油,来源于腐殖型有机质,和克拉苏构造带及塔中1气田来源于腐泥型有机质的湖(海)相原油存在明显差别。综合上述分析,乌什凹陷原油主要为来自于侏罗系煤系烃源岩的煤成油。
The successive breakthroughs of the Wushen 1 well, Shenmu-1 well and Shenmu-2 well in the Wushi depression of Tarim Basin reveal that the area has broad prospect of oil and gas exploration. The geochemical characteristics of crude oil in Wushi depression were analyzed comprehensively by gas chromatography of saturated and light hydrocarbon, and compared with the typical crude oil and lake (sea) phase crude oil in Tarim Basin. The Pr / Ph of the wells of Shenmu-2 and Wushen-1 wells are 2.35 and 3.53, respectively, showing typical features of coal-forming. Crude oil in Wushi Depression has a relatively high content of aromatic hydrocarbons (benzene and toluene), methylcyclohexane and cyclohexane, while the relative content of cyclopentane and acyclic hydrocarbons is relatively low, indicating that terrestrial organic matter contributes more. The Wushi Sag crude oil heptane index is between 25.0% ~ 27.6%, isoheptane index is between 2.5% ~ 2.7%, in the early stages of high maturity. Wushi depression crude oil did not experience washing and biodegradation, but the more obvious evaporation fractionation, resulting in aromatics content of light hydrocarbon components increased, while n-alkanes decreased. According to the OCSD-C7 light hydrocarbon star chart and the C7 light hydrocarbon system triangle diagram, the oil in the Wushi depression and the condensate in the Dina 2 gas field belong to the continental oil, which is derived from the humic organic matter and the Krasuba tectonic belt and the tower The Zhong 1 gas field is obviously different from the lake (sea) phase crude oil of sapropelic organic matter. Based on the above analysis, the oil in the Wushi depression is mainly derived from coal-derived oil from the Jurassic coal measure source rocks.