Abstract: Based on the integrated study on the source rocks,expulsion driving force,vertical migration pathway,and reservoir of Anda Depression in the northern part of Songliao Basin,this paper identifies the main controlling factors of mid shallow layers′ hydrocarbon accumulation and achieves a big exploration breakthrough of Anda Depression.This study reaches four conclusions as follows:1.The maturity of source rocks is the most important controlling factor of hydrocarbon accumulation and it determines the distribution and scale of the mid shallow oil pools;2.The overpressure of the 1st member of Qingshankou Formation in the mature source rocks is the main controlling factor of hydrocarbon accumulation of the 4th member of Quantou Formation;3.As for the Qingshankou Formation,the vertical migration pathway is the basis of the hydrocarbon accumulation and the developing level of the 2 nd and 3 rd reservoir of Qingshankou Formation is the key factor of hydrocarbon accumulation;4.The relatively low maturity (the Ro of most Anda Depression is less than 0.9%) and thin thickness (the thickness of most Anda Depression is less than 80m) of source rocks result in the relatively low generating hydrocarbon potential,which may control the hydrocarbon accumulation of Yaojia Formation.

Key words: overpressure, source rock, main controlling factor of hydrocarbon accumulatio, Anda Depression, Songliao Basin