东海盆地丽水凹陷原油地球化学特征及油源分析

原油地球化学特征综合分析表明,丽水凹陷a井原油异构烷烃含量极高,b井原油富含环烷烃,c井原油环烷烃含量相对较高;原油碳同位素以a井最轻,b井最重,c井介于二者之间;各井原油的伽马蜡烷含量较高,五环三萜烷Ts、C29Ts和C30重排藿烷含量也较高,以规则甾烷为主,重排甾烷含量很低。通过与凹陷内3套烃源岩生物标志化合物特征的对比研究,认为丽水凹陷原油均有月桂峰组烃源岩的贡献;a、c井原油主要来源于月桂峰组烃源岩,但其烃源灶区可能不同;b井原油是月桂峰组和灵峰组烃源岩生成烃类的混合产物,其中高碳数烃类主要来源于月桂峰组烃源岩,部分来源于灵峰组烃源岩,中低碳数烃类来源于月桂峰组和灵峰组烃源岩。

An analysis of oil geochemistry and sources in Lishui sag, East China Sea basin

According to a comprehensive analysis of oil geochemistry in Lishui sag,oil in Well A is extreme high in isoalkane content,oil in Well B is rich in cycloalkanes and oil in Well C is relatively higher in cycloalkane content.For the carbon isotope of oil,Well A is lightest,Well B heaviest and Well C between Well A and B.In the three wells,oil is quite higher in the contents of gammacerane,pentacyclic triterpane Ts and C29Ts and C30 rearranged hopanes,but the sterane is dominated by its regular form,with the content of its rearranged form very low.Based on a comparison of biomarkers between three sets of source rocks in Lishui sag,it can be considered that the source rock of Yueguifeng Formation has contributed to all oil in the sag.Oil in Well A and C comes mostly from the source rock of Yueguifeng Formation,but may have different hydrocarbon kitchens.In contrast,Oil in Well B is the mixture of hydrocarbons generated from the source rocks of Yueguifeng and Linfeng Formation,with its high-carbon-number hydrocarbon mostly from Yueguifeng Formation and partly from Linfeng Formation,and its middle-low-carbon-number hydrocarbon from both Yueguifeng and Linfeng Formation.