Abstract: Hydrocarbon generation potential of source sag controls oil/gas prospecting potential in a petroliferous basin.There was very close relation between feature of sag and fill sequence.Eight secondary sags were developed in Tangyuan depression, among which the difference between basement feature and its controlling on fault movement resulted in different types of sedimentation and fill characteristics.Based on analyses of formation and evolution regularity and formation fill sequence of each secondary sag in Tangyuan depression, this paper summerized three models for secondary sag and fill sequence.On the basis of analyses of development of source rock and source-reservoir-cap assemblage characteristics, oil/gas prospective potentials of different types of sag were predicted.

Key words: Tangyuan, Fault depression, Sedimentation, Sequence, Source-reservoir-cap assemblage, Oil and gas exploration