Abstract: According to the geological data, the formation process of heavy oil in Taobao area is studied, by using geochemical techniques. It is considered that the crude oil of the area began from the Qingshankou Formation of the central sag in the east, migrated for about 50 kilometers and was hindered by the Taobao adverse fault and at last was accumulated in the area. Because of long distance migration, the bed absorbing process and filtration of the reservoir leads to the low freezing point and low asphaltene of crude oil. Meanwhile, the crude oil gets heavy and dense and of high resin, due to oxidation, water washing and biodegradation of formation water. Thus the crude oil has certain characteristics of heavy oil.

Key words: Songliao Basin, west slope, Taobao, heavy oil, carbon isotope, oil and source rock correlation