Study On Sedimentary Microfacies Of Large Submersible Bar Condensate Gas Field And Reservoir In Kuqa Depression

Kuqa depression is the key area of oil and gas exploration in the north of Tarim Basin,which is rich in oil and gas resources and has a good prospect of oil and gas exploration.The study area of this paper is located in the north of Kuqa depression,which is a compound fault anticline structure,and the main reservoir is deeply buried.There are good oil and gas shows in Suweiyi formation and Bashijiqike formation of the target interval,with great potential.However,the basic geological knowledge of stratigraphic correlation,sedimentary facies types and distribution characteristics of sedimentary facies has not been unified,and the overall research level is relatively low.It is of great significance for the exploration and development of oil and gas in this area to carry out the basic geological research work of sedimentary micro equivalence.According to the data of drilling coring,logging curve and seismic data,combined with the regional geological background,the paper determines the sequence boundary identification mark of the target layer,completes the stratigraphic division and correlation of twenty-two wells in the study area,establishes a complete isochronous stratigraphic framework,divides the Suweiyi formation into two sections with four small layers,and the Bashijiqike formation into three sections with eight small layers.Through the comprehensive analysis of multi-source such as structural geological background,seismic stratigraphy,lithofacies paleogeography,sand body inversion and sand mud ratio.Suweiyi formation has the characteristics of beach bar deposition,the provenance of the dense well pattern area comes from the east,and the provenance of the sand body in the south comes from the southeast of the study area.The provenance of Bashijiqike formation is mainly from the southeast of the study area.Through the comprehensive analysis of core facies,logging facies,seismic facies and lithofacies paleogeographic background,the sedimentary facies types of the target strata in the study area are identified again.Among them,the subfacies of lakeside and shallow lake developed in Suweiyi formation,including four types of microfacies:lakeside sand bar,lakeside sand bar,lakeside mud and lakeside mud;the sand body is dominated by the sedimentary microfacies of lakeside sand bar and lakeside beach bar,and the sand bar is mainly extended from east to west.In Bashijiqike formation,shallow water delta lacustrine depositional system is developed,mainly including three microfacies: underwater branch channel,hekou bar and inter channel bay;thesand body is mainly composed of underwater branch channel and hekou bar of shallow water delta front subfacies,which are affected by shallow lake water body,and the sand sediment sheet is obvious.The underwater branch channel mainly extends from southeast to northwest and from north to south,hekou bar is mainly distributed from northeast to southwest.The sandstones of Suweiyi formation are mainly brown powder fine feldspar quartz sandstones,lithic quartz sandstones and quartz sandstones.The pore types are primary intergranular pores and expanded intergranular dissolution pores,which belong to medium porosity and medium permeability reservoirs.The sandstones of Bashijiqike formation are mainly feldspathic quartz sandstones and lithic quartz sandstones.The pore types are mainly expanded intergranular dissolved pores and primary intergranular pores,both of which belong to medium porosity and medium permeability reservoirs.The control of sedimentary micro relative reservoir mainly lies in its control of physical properties,including sandstone separation,roundness,etc.Among them,two microfacies in the middle and margin of the shore shallow lake bar in the Suweiyi formation in the study area are the reservoirs with better physical properties;distributary channel and hekou bar are two microfacies with better physical properties in the Bashijiqike formation.