Single Sand Body Characterization Of Baijiantan Formation In Middle-East Seven Area Of Junggar Basin

Oil and gas resources are stored in sand bodies,which are the most important objects in oil exploration and development.The quality of sand bodies and the spatial location of sand bodies have a vital impact on oil and gas reservoirs,so sand bodies are the core of oil and gas reservoir exploration and development.As the main horizon of the key research block of No.2 Oil Production Plant of Xinjiang Oilfield,Baijiantan Formation in the Middle-East Region has been exploited and developed for more than 60 years since industrial oil flow was obtained in 5013 well in the East in1960.By 2015,after five stages of oil testing and production,productivity construction,productivity decline,low-speed stable production and adjustment and development,215 wells have been drilled,and recoverable reserves are still comparable.It has high prospects for exploration.However,with the improvement of exploration and development,the reservoir has entered the stage of high water cut development.Although a large number of oil and water wells have been injected in the adjustment stage,and the well pattern density is increasing,there are still some problems in the work area at present:the description results of local sedimentary microfacies do not conform to the actual production;the reservoir exploitation stays at the level of sand formation,and the configuration of single sand body in the sand formation is complex,which leads to injection and production wells.The potential of the network has not been fully exploited,and water channeling occurs in individual wells.The injection-production development policy needs to be further optimized.Therefore,it is of great significance for oilfield production to study the sedimentary characteristics and fine characterization of single sand body of Baijiantan Formation.Based on reservoir geological characteristics and sequence stratigraphy theory and method,delta front facies stratigraphic correlation is made by taking into account such factors as base cycle,marker layer?standard layer?and sand body superimposition.T₃b₁⁴ is divided into T₃b₁^4-1 and T₃b₁^4-2 sublayers,T₃b₂¹ into three sublayers,T₃b₂² into seven sublayers,a total of 12 sublayers,which lays a good foundation for single sand body characterization and reservoir geology research.In terms of sedimentation,through drilling,logging,coring data and previous geological research results,sedimentary facies markers are identified,and the types of microfacies developed in the Baijiantan Formation in the study area are defined.Two facies,three subfacies and eight microfacies are identified.The favorable micro-phase is in the small layers of T₃b₂^2-6,T₃b₂^2-5,T₃b₂^2-4,T₃b₂^2-2 and T₃b₂^1-2,and the underwater distributary channel and mouth bar are developed.T₃b₂^2-1 and T₃b₁^4-1 interbay microfacies are two sets of main barriers in the reservoir.Based on the results of fine correlation of small layers,sedimentary environment and sedimentary microfacies,the identification of single sand body in the sand formation of the study area is carried out,the identification marks of single sand body are determined,and the genetic model of the list sand body is established.The single sand body is revised and verified by combining production dynamic connectivity data and production-suction profile,and the plane distribution rule of single sand body is determined.69 sets of single sand bodies are identified in the small layer.Single sand bodies are most developed in T₃b₂^2-2.The single sand body can be divided into three types according to its shape:sheet,branch and finger.Among them,the flake sand body is the largest,which belongs to the migration superimposed channel origin,mostly located at the root of subfacies in the delta front;the single sand body is determined to be 2-5 meters thick and 10-50 meters wide;and the migration superimposed channel origin sand body is 50-550 meters wide.The vertical contact relationship of single sand body can be divided into four types:separated type,superimposed type,cut-and-overlap type and substitution type.On the plane,there are three types:Bay contact,docking type and side-cut type.