Structural And Reservoir Characterization Of The South Part Of The Shunbei No.5 Strike-slip Fault Zone,Tarim Basin

Newly discovered superdeep marine carbonate reservoirs with burial depths of more than 7,000 m are found in the Shuntuo Low Uplift,Tarim Basin,China.Previous exploration experience indicates that strike-slip faults in these deposits played a key role in reservoir formation and hydrocarbon accumulation.The multi-stage activity of strike-slip fault development of a Riedel shear fracture system has enhanced the karstification process.A fracture–cavity type reservoirs was formed in the carbonate rock strata under 7,000 m depth.The discovery of this oil and gas accumulation has opened new possibilities for hydrocarbon exploration in deep-marine carbonate reservoirs.In this research,based on the study of high-quality 3-D seismic volumes,drilling datas,and outcrop datas,the structural and hydrocarbon characteristics of the SB5 M strike-slip fault zone in the Shuntuo Low Uplift were investigated in detail.The south part of the Shunbei No.5 strike-slip fault zone is an atypical multi-reactivated intracratonic strike-slip vertical fault zone.In the Paleozoic,the south part of the Shunbei No.5 strike-slip fault zone was composed of sub-vertical strike-slip faults in the deep layer,a graben structure in the middle layer,and en-echelon normal faults in the shallow layer.By analyzing the vertical separation of strata,calculating the growth indices of the faults,and studying the strata changes caused by the faults,it was determined that the faults developed in the deep,middle,and shallow layers were controlled by Middle Caledonian,Late Caledonian,and Middle–Late Hercynian movements,respectively.South part of the Shunbei No.5 strike-slip fault zone developed the “Fault-Karst” farcturecavity resevoir.This type of farcture-cavity reservoir developed as a result of the interplay between faulting and karstification.Affected by multistage tectonic movements,the south part of the Shunbei No.5 strike-slip fault zone connected with the source rocks of the Lower Cambrian Yuertus Formation and throughout the Paleozoic strata,and thus served as hydrocarbon migration pathways and accumulation traps.The development of the strike-slip "fault core and fracture zone system" and graben structure led to great heterogeneity in the reservoirs controlled by the south part of the Shunbei No.5 strike-slip fault zone.