QDN Basin is an extensional basin which fractured first and then depressed.The basin could be divided into 5 second order sequences and 19 third-order sequences.The basin's chronostratic framework was built according to basin's evolution history and formation characteristics.Two source reservoir cap rock assemblages were discovered in the basin.The lower assemblage consists of several source beds such as lake and transitional facies of the Eocene Series and Yacheng Formation;the reservoirs are mainly fan delta

sand beach

sand bars

foreset wedges and slope fans.The source rocks of the upper assemblage are the dense section of Meishan Formation

the shallow-abysmal argillaceous sediments of Yinggehai Formation;the reservoirs are deltaic sandbodies on continental slope.The regional cap rocks of the both are thick mudstone of the Yinggehai Formation and the abysmal ar gillaceous sediments of the Meishan Formation.It is considered that the basin possesses favourable hydrocarbon potential.