The Study On Jurassic Sedimentary Facies In The Western Margin Of Chepaizi Area,Junggar Basin

Chepaizi area is an important oil and gas enrichment area in Junggar Basin.The exploration degree of Jurassic in the western margin of Chepaizi area is relatively low at present.The study of sedimentary type and distribution will lay a foundation for further exploration and deployment.In this paper,the sequence stratigraphy and sedimentary equivalence of Jurassic in the western margin of Chepaizi area,Junggar Basin,have been studied by means of comprehensive analysis of core,logging,seismic and laboratory data.Based on the combination of well and seismic data,the sequence stratigraphic framework of the Jurassic in the study area is established,and two second-order sequences,four thirdorder sequences and eight system domains are divided.On this basis,the types of sedimentary facies are divided,and the subfacies of the braided river delta and the subfacies of the shallow lake of the shore are identified,the former is mainly distributed in the north and middle of the study area,and the latter is mainly distributed at the periphery of the study area.It is considered that the plane distribution of sedimentary facies in different system tracts of Jurassic sequences in this area has a strong inheritance,but there are local differences.According to the drilling data,the distribution range of Jurassic sequence sand bodies in the study area is carried out,among which the braided river delta sand bodies of Sangonghe formation and Xishanyao formation are most widely distributed.Based on the analysis of the spatial association relationship among sand body,unconformity surface and strata tip-out line,the types of subtle traps and favorable development areas of different formation segments are implemented.It is considered that there are mainly structural traps in this area.Structural-stratigraphic lithologic traps and stratigraphic lithologic traps are three types.Finally,combined with the preliminary exploration results of Chepaizi area,the conditions of trap formation are comprehensively analyzed,and the unconformity covering-lithologic trap zone in the northeast of the study area and the nose-shaped structure-lithologic trap zone in the central Su-6 well area are predicted.Su-14 well nose-like structure-lithologic trap zone 3 favorable exploration zones.