Abstract: In order to study the distribution law of oil and gas near oil source faults in petroliferous basins, based on the study of formation mechanism and period of associated traps of oil source faults, the initial formation period of associated traps of oil source faults is determined by the fracture initiation period and segment growth connection period reflected by the fault offset-displacement curves of oil source faults in different geological periods. The formation period of lateral sealing of oil source fault is determined by the relationship between displacement pressure of oil source fault rock and displacement pressure of oil and gas migration disk reservoir rock with time. A set of methods for determining the formation period of associated traps of oil source fault is established by superimposing the two methods, and it is applied to the determination of the formation period of associated traps of Dazhangtuo fault in the Es₁^x formation in Qikou sag, Bohai Bay Basin. The results show that the associated trap formation period of Dazhangtuo fault in Es₁^x formation is 2.35 Ma, although it is later than the period when the source rocks of the Es₃ formation discharge a large amount of oil and gas, but it can still capture a large amount of oil and gas discharged from the source rocks of the Es₃ formation, which is more conducive to the accumulation of oil and gas discharged from the underlying source rocks of the Es₃ formation in Es₁^x formation near Dazhangtuo fault. It is consistent with the oil and gas distribution found in the Es₁^x formation near Dazhangtuo Fault, which indicates that this method is feasible to determine the formation period of associated traps of oil source faults.

Key words: oil source fracture, associated trap, formation period, determination method