Reservoir Characteristics And Controlling Factors Of Jurassic Coal Measures In Wucaiwan Sag, Junggar Basin

Aiming at the low exploration degree and great exploration potential of Jurassic reservoirs in the study area,this paper focuses on the reservoirs of the Jurassic Badaowan Formation and the Xishanyao Formation in the Wucaiwan Sag,Junggar Basin.Based on sedimentology and oil and gas reservoir geology,the field outcrop observation,logging,logging data and laboratory core analysis were used to comprehensively study the microscopic pore structure,microscopic seepage characteristics and diagenesis of reservoirs.The main factors controlling the physical properties of the reservoir were analyzed,and the reservoirs were classified and evaluated.A set of lacustrine-river facies sedimentary deposits was developed in the Badaowan Formation of the study area.The Xishanyao Formation is mainly a set of peat swamps and covered marshes deposited after lake sedimentation.The reservoir lithology of the Badaowan Formation in the study area is dominated by siltstone,followed by mudstone and fine sandstone,and also contains a small amount of medium sandstone and conglomerate.Low component maturity,the pore type is mainly intragranular dissolved pores and residual intergranular pores.The type of support between particles is mainly supported by particles.The lithology of the Xishanyao Formation is dominated by fine sandstone,followed by siltstone and mudstone,with the least conglomerate and low component maturity.The pore type is mainly composed of intergranular dissolved pores and residual intergranular pores.The contact and the point-line contact are mainly,and the contact is less than the bump;the support type between the particles is mainly the particle support type.The formation of the Xishan Kiln in the study area is mainly from the Early Diagenesis A to the Zhongchengyan B.The reservoirs of the Badaowan Formation in the study area should be ultra-low pore and ultra-low permeability reservoirs.The reservoirs of the Xishanyao Formation are mainly ultra-low porosity and low permeability reservoirs.Through the analysis of mercury intrusion data,the reservoir pore characteristics of the Badaowan Formation and the Xishanyao Formation in the study area are basically the same.The reservoir physical properties are mainly controlled by the rock types,sedimentary microfacies,diagenesis and micro-fractures of the reservoir rocks.As the particle size decreases,the physical properties of the reservoir become worse.Compaction and cementation are the main causes of reservoir compaction.The dissolution and micro-cracks improve the physical properties of the reservoir.