Geochemical characteristics of the mixed oil in western slope belt of Dongpu Depression

The geochemical characteristics of the crude oil in the studied area are different from those of the oil in other areas of the depression.The systemical analyses of the saturated hydrocarbon composition,aromatic composition and biomarkers of the crude oil show that,the type of the oil-generating organisms of the crude oil is good,the majority of which is low-grade hydrobionts and the minority of which is high-grade terrigenous plants.There is high content of gammacerane in the oil,phytane predominates in isoprenoid alkenes,which indicate the paleoenvironment of source rocks is reductive brackish-salt lake facies.The maturity parameters of the crude oil are inconsistent,which indicates the oil is not immature oil but is mixed oil,and the majority of the oil comes from the mature source rock of Shahejie Formation.