Based on the crude oil, saturated hydrocarbon chromatography, mass spectrometry, biomarkers and other information, the characteristics and distribution of crude oil in western Bozhong Sag were analyzed. With the comparison and analysis of the oil source, the main controlling factors of oil densification were discussed. The results show that the crude oil of Guantao Formation has the characteristics of zonal distribution on the plane. The crude oil is gradually getting better towards the sag. The crude samples in Guangao Formation have the characteristics of "four high and two low". The lower limit of occurrence is about 2,000 m. The thermal evolution of source rocks is high, and the crude oil is mature in the western Bozhong Sag. The secondary oil thickening action dominated by biodegradation is widely developed in the research area. The late filling of high wax content oil and anti-degradation in Dongying Group is the main controlling factors of oil densification in the western Bozhong Sag. On one hand, the early thickened crude oil has been "diluted", and the crude oil has been improved. On the other hand, the wax content of mixed crude oil is increased and has certain anti-degradability, which is an effective guidance to the exploration deployment of light oil and gas exploration in western Bozhong Sag.
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