渤海湾盆地南堡凹陷滩海地区奥陶系原油油源分析

Source Analysis of Oils from the Ordovician in the Shoal Zone,Nanpu Sag,Bohai Bay Basin

近年来渤海湾盆地南堡凹陷的油气勘探取得了重大突破。在滩海区奥陶系古潜山钻遇工业性高产油气流,使奥陶系古潜山成为南堡油田重要勘探目的层之一,但目前对奥陶系主要产油层中油气的来源问题仍存在着不同的认识。通过对奥陶系原油与古近系沙三段、沙一段和东三段3套烃源岩的地球化学特征进行对比研究,并结合奥陶系油气成藏特征,探讨了奥陶系原油的油源。结果表明:南堡油田奥陶系原油生物标志化合物特征和稳定碳同位素组成与沙三段烃源岩的相似,二者具有较好的亲缘关系;同时,区域性的不整合面、油源断层可以成为沟通奥陶系古潜山储层与沙三段油源的运移通道;奥陶系原油主要来源于沙三段烃源岩。

The Ordovician Formation is the main oil reservoir of deep strata in the Nanpu oilfield in the northern Huanghua depression,Bohai Bay basin.At present,there are some different points of views about the distribution of the source rocks contributing to this reservoir.The geochemical characteristics of saturated hydrocarbons and carbon isotopes in source rocks,crude oils and extracts in some sandstones from oil-bearing strata in the regional interest areas have been investigated in this paper.The contribution of source rocks in the first and third members of Shahejie Formation to petroleum accumulation in the reservoirs of the Ordovician Formation,Dongying Formation in the region has been discussed too.The results show that the crude oils in the reservoir of the Ordovician Formation mainly derived from the source rocks in the third member of Shahejie Formation.