Abstract:

Abstract: Shenxian Sag is situated in the east part of Linqing Depression in Bohai Bay Basin. The main source rocks are Sha-1, Sha-3, Sha-4 members and the Kongdian Formation. The late depositional stage of the Guantao Formation was the peak stage of oil generation and expulsion of the source rocks and also the critical period of the formation of petroleum systems. According to oil shows and oil source correlation, the Lower Tertiary in the sag could be divided into two petroleum systems: 1. the known Sha-3 menber pertoleum system which contains two subsystems such as the lower Sha-3 submember and the middle and upper Sha-3 submember subsystems. Oil pools of Jia-2 Well and Sherr4 Well were discovered in the first subsystem but no oil shows have been found in the last subsystem; 2. the deduced petroleum system of Sha-4 member and the Kongdian Formation could be divided into Sha4 member subsystem and Kongdian Formation subsystem, and no oil shows have been discovered in the second subsystems. The oil pools developed within the petroleum systems are mainly srtuctural oil pool, structural lithologic oil pool and lithologic oil pool which were formed in Miocen Epoch. The distribution of oil pools are controlled by hydrocarbon generation sag,hydrocarbon genera-tion stage and fault sealing ability. It is considered that circumsag belt in Tangyi Subsag is favourable for hydrocarbon pool formation.

Key words: petroleum system, Lower Tertiary System, oil and gas pool, Shenxian Sag