Study On Petroleum Accumulation System Of Complex Fault Block Oilfield

Hongshangzui oilfield in the northwestern margin of Junggar Basin faces a complex oil gas distribution,which can be found from the Carboniferous to the Cretaceous with normal crude oil,heavy oil as well as light oil reservoirs,even though dry gas reservoirs appeared in Hongche fault;as well as confusing formation water spreading.Hongshanzui Oilfield formation water distribution is very puzzled,gas and water distribution influenced by complex control factors,in which resulted big chanllege in oil gas exploration and development,in order to provide practical significance for complex fault block reservoir accumulation for optimization and guide further exploration and development programs,it is necessary to carry out field research on the oil gas accumulation system,as well as formation water distribution and the related research.This paper describes the plane distribution and vertical variation of formation water of the Hongshangzui oilfield in the northwestern margin of Junggar Basin for the purpose of investigating hydrocarbon migration and accumulation of oilfield.After contrast research on geochemical features of Hongshanzui oilfield crude oil sample,it is found that Hongshanzui oil field crude oil come form a single source,which comes from Fengcheng group of Permian Changji sag in Wuerhe area with low-mature.The resulted showed that crude oil in Hongshanzui oil field is source from the Permian Fengcheng Formation in Wuerhe areas and migrates with a path of S-N trending faults and unconformities that formed in the Yanshanian movement.Comparison of distribution of hydrocarbon reservoirs and chemical feature of formation water indicates that preserved environments of formation water is an indicative of hydrocarbon reservoirs directly and enclosed environment indicated by formation water was proved that good hydrocarbon reservoirs existed.The contact between the Carboniferous and the Cretaceous is an fault caused by the Yanshanian Movement.The comparison of formation water properties between the hanging wall and foot wall of fault show that N-S trending faulted zone formed post-Yanshanian Movement is under an stretching and the northern segment of the Hongche fault zone has poor sealing condition which resulted in a lost of hydrocarbon and light oil reservoir somewhere.Analyses of crude oil density distribution and saturated hydrocarbon gaschromatography shows that a heavy oil zone formed by washing and biodegradation.But the northern segment of the Hongche fault belt.As for,due to the huge thick layer mudstone sealing of the Baijiantan Formation,the southern segment shows better hydrocarbon preservation conditions.A good faulted reservoir formed under a sealing by the E-W trending fault.After synthetic study on the characteristics of formation water and reservoir accumulation system,reveals that the big fault which is the main facters controlled the resevior distrubition of Hongshanzui oilfield.Crude oil along with the unconformity surface and Yanshanian tectonic movement formed nearly NS-trending fault zone migrated from southeast to northwest.Near the source rock area formed high pressure reservior,where oil and gas migration along the fast advantage channel accumulation,Hongshanzui oilfield with a vertical oil and gas transportation systems composed by fracture system and unconformity,oil and gas through the three-dimensional conducting system from low position to high position,from deep to shallow migration,and gathered into a hidden trap.