Geochemical features and oil-source correlation of crude oils from JZ20 oil field on the northern margin of Liaoxi Uplift,Bohai Bay Basin

The Liaoxi Uplift is one of the regions with the highest level of exploration in the Liaodong Bay area of the Bohai Sea. Geochemical analyses were carried out on crude oil samples from the Shahejie and Dongying formations in the JZ20 oil field on the northern margin of Liaoxi Uplift. The physical properties, hydrocarbon group composition, maturity and biomarker characteristics of crude oil were studied, based on which an oil-source correlation was made. The crude oil is light with a low maturity and low sulfur content. The saturated hydrocarbon chromatograms of the oil are distributed fully, indicating no biodegradation. The organic matter source is mixed with a minor terrigenous input to the crude oil in the Shahejie Formation and a significant terrigenous organic matter input to the crude oil in the Dongying Formation. The source rock was deposited in an anoxic to suboxic and brackish or saline water environment. Crude oil of the Shahejie Formation originated from the third and the first members of Shahejie Formation in the Liaoxi Sag. Crude oil of the Dongying Formation originated from the third member of Shahejie Formation in the Liaoxi Sag and the third member of Dongying Formation in the Liaozhong Sag. In addition, crude oil of the Dongying Formation is characterized by a double-sag hybrid source hydrocarbon supply.