Abstract: The north margin of Qaidam basin is an old oil region. The Middle and Lower Jurassic strata are its main source rocks. Through regional studies, the Jurassic is divided into 3 series and four formations, i.e. Xiaomeigou formation of Lower Jurassic, Dameigou formation of Middle-Lower Jurassic and Hongshuigou formation and Caishiling formation of Upper Jurassic, of which Dameigou formation can be subdivided into 7 members. This paper presents the classifications and correlations of 38 wells encountered into the Jurassic one by one, and reviews the sedimentary characteristics of Lower Jurassic and Middle Jurassic, based on which the petroleum systems of the Lower Jurassic and the Middle Jurassic. It is concluded that the Lenghu-Nanbaxian arc structural belt and the Eboliang structural belt are favorable areas for petroleum exploration.

Key words: Qaidam basin, north margin, Jurassic, stratigraphic correlation, petroleum system