The Sedimentary Facies And Reservoir Characteristics Of Chang6 In WeiJiaWan Area Of NanNiWan

Nan Ni Wan is located in the area of Wei Jia Wan Gou,Pine forest Township,BaoTa District,Yan'An City,Shaanxi Province.At present,this block has entered the middle and late stage of development,and the water content has increased obviously,but the basic geological research in this area is relatively weak,especially in the aspects of sedimentary micro-facies and reservoir physical property control factors.In order to improve EOR?Enhanced Oil Recovery?and provide theoretical support for the later exploration and development of oil fields,this paper carried out an in-depth study of the study area.This paper is guided by many disciplines such as sedimentary petrology,reservoir sedimentology and structural geology.Through the comprehensive use of logging,core,scanning electron microscopy analysis,thin section analysis,mercury intrusion analysis and other data,Chang6 oil layer group has been deeply studied from the aspects of stratum characteristics,structural features,sedimentary microfacies characteristics and reservoir characteristics,and made the following conclusions:In reference of Yan Chang formation in Ordos Basin,on the basis of stratigraphic division and correlation plan,this thesis mainly adopts the principle of"small"big first,mark layer principle,principle of adjacent Wells contrast and etc.,the principle of thickness when the method of combining to Nan Ni Wan,Wei Jia Wan wellblock Chang6 sedimentary period of the three reservoir group leader,Chang6₁,Chang6₂,Chang6₃ are further divided into Chang6₁¹,Chang6₁²,Chang6₂¹,Chang6₂²,Chang6₃¹,Chang6₃²,Chang6₃³seven small period;The stratigraphic correlation results show that the Chang6 formation in Wei Jia Wan area has stable development and little change in thickness.Through the research of sedimentary facies,Chang6 sedimentary period belongs to delta front subfacies,the main development of the underwater distributary channel and distributary bay between two sedimentary micro-facies and sand body thickness of about 5 meters to 10meters,the north east�south west of the zonal distribution,the source direction,debris supply is adequate,underwater distributary channel net-like distribution along the source direction,and between distributary bay spacing distribution of sand body connectivity,extends far.The lithology of reservoir in the study area is mainly gray fine-grained arkose and medium-fine-grained arkose.Good separation and general roundness;Most of them are primary and secondary pores,and the pore structure is mesopore�micro throat type and mesopore�micro throat type.The interstitial materials are mainly of argillaceous complex content,and the cementation type is mainly of pore type.The average porosity of the Chang6formation is 10%,and the average permeability is between 0.45mD to 1.0md,belonging to the low-porosity and ultra-low-permeability reservoir.Reservoir heterogeneity is moderate.According to the reservoir classification standard,the Chang6 sedimentary period of sedimentary facies,sand body distribution and reservoir characteristics of comprehensive analysis,it is concluded that the study area are mainly?,?reservoir.According to the reservoir classification standard,the small layers in the study area are classified as follows:Chang 6₁²,Chang 6₁¹ small layer is the best small layer with Chang 6porosity,mainly developed type II reservoir,local development type I reservoir;Chang 6₂² The small layer body mainly develops type III-class II-b reservoirs;the Chang 6₂¹small layer mainly develops type II reservoirs;the Chang 6₃³ and the Chang 6₃² small layers are low porosity and low permeability reservoirs,mainly developing type III reservoirs;The layer is dominated by the development of type III reservoirs,and the middle class II-b reservoirs are developed.