Abstract: The concept of syngenetic fault is known as growth fault or synsedimentary fault. Through the studying on the syngenetic fault in offshore area of the Dagang Oilfield, it is found the in-ternal syngenetic faults had segmented growth feature clearly,they grew segmentedly, and connected to one fault finally. The segmented growth feature of the syngenetic fault in the depres-
sion had the different control on the stratigrphic sedimentation,hydrocarbon migration and accumulation. Which makes that in the same hydrocarbon-bearing system, also in the samefault and horizon, just in the different location, the hydrocarbon migra-tion and accumulation pattern different. Segmented study on the syngenetic fault in the depression is of important practical meanings to guide the field exploration and production.

Key words: Rift Basin, syngenetic fault, refraction, off-shore area of Dagang, Zhangdong Fault, sealing