Research On Sedimentary Facies Belt And Reservoir Characteristics Of Yijianfang Formation Of Ordovician In Tabei Area

This paper,based on plenty of documents in the world,according the theories such as carbonate reservoir geology,carbonate reservoir characterization and carbonate reservoir lateral prediction,and combined with the macro and micro technologies,on the basis of detailed core observation and thin section identification,adequately applying with drilling,logging data,well logging and seismic data,takes the Yijianfang formation of Middle Ordovician in the north tarim area as the research object,studys the stratum spatial distribution,sedimentary facies types and its development characteristics,reservoir characteristics and its main controlled factors,reservoir prediction and so forth.First of all,combined with regional tectonic evolution,logging and seismic data,the stratum of Yijianfang formation is divided and compared,as well as its spatial distribution.Through the core observation and thin slice identification analysis,combined with the identification of various sedimentary facies,it is found that the Yijianfang formation is mainly composed of the open platform facies,which are divided into platform beach,beach sea,platform point reef,and so on.Horizontally,the platform beach is thick and continuous.The beach sea,which is caught in the beach in form of lens,is less developed and developed in the specific stratum;Vertically,the platform beach and the beach sea are interleavely developed,which are the characteristics of geocyclicity.According to the study of reservoir space types and physical characteristics of Yijianfang formation,it mainly develops vuggy reservoir and fractured-vuggy reservoir,cave reservoir mainly develops in the middle-upper stratum.In addition,based on the reservoir evaluation standard,the Yijianfang formation is evaluated ????? levels,which is mainly developed the second level.Meanwhile,the reservoirs are mainly distributed in the middle-upper of the Yijianfang formation,which are horizontally traceable and compared.In the study area,the reservoir of Yijianfang is controlled by palacogeomorphology,diagenesis and tectonism,etc.Among them,the palaeogeomorphology indirectly determines the lithology and lithofacies,otherwise,the lithology and lithofacies are the material basis of the reservoir development;dissolution is the main control factor of the quality of the reservoirs,tectonism effects the permeability and connectivity of reservoir's stored energy.Those are the factors which effect the evolution of the reservoir of Yijianfang.The favorable exploration zones in the studied area of Yijianfang are predicted with the comprehensive analysis of various factors,combined with a variety of methods.It is found that the effective porosity distribution of reservoir is matched with the geologic feature can.That is,in upper location of the structure,its porosity is higher than other tectonic positions;at the same time,the higher porosity,the thicker effective stratum.Furthermore,the favorable reservoir development zone is distributed along the fracture-developed zone,while the underdeveloped regions are mainly distributed in the low energy facies and low fracture-developed zone.Overall,these conclusions can provide geologic theoretical foundation for the exploration and development of the Yijianfang formation.