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

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.