Abstract: According to comprehensive analysis of data from core lab, logging and well logs,the Chang?7member of Yanchang formation of Upper Triassic in the study area can be dividedinto three types of source?reservoir lithologic assemblages such as source sandwiching reservoir(Type1), source?reservoir interbed (Type2) and reservoir sandwiching source rock (Type3). This Paper indicates that such assemblage types have important effects on expulsion and charging of tight oil, based on studied results of source rock thickness, internal fluid pressure feature,geochemical analysis and effective oil charging space coefficient. The former two types have micro?fracture episodic hydrocarbon expulsion and incomplete expulsion, the third type is one with complete expulsion. For the tight oil enrichment extent, Type1is high, followed by Type2, Type3is relatively poor.