Research On Sedimentary Facies,Reservoir Characteristics And Advantageous Regions Prospecting Of Chang6in T29-T38 Well Area,Wuqi Oilfield

29-38 Area of Wuqi Oil field is located in the western part of Shanbei slope and it is the secondary structural unit of Ordos basin.This paper mainly studies Chang 6reservoir.The geological conditions in the study area are rather complex,characterized by multilayered oil bearing formations with strong lateral and vertical heterogeneity.Therefore,this paper studies sedimentary micro-facies,then in order to predict favorable area,reservoir characteristics are studied,classificated and evaluated.The paper aims to grasp the reservoir characteristics,and providing the basis and some guidance for the further development plan.The paper takes the petroleum geology,sedimentary petrology,structural geology as basic.The paper uses the date of core analysis and well logging to complete stratigraphic comparison and division.Based on the study of regional geological background,the paper analyzes various facies marks which reflects the sedimentary characteristics,then analyzes log facies and confirm the types of sedimentary micro-facies.The samples were characterized by slice observation,grading analysis,scanning electron microscope and mercury porosimetry.Based on the experimental data,rock type,pore type,pore structure,physical properties and reservoir heterogeneity and other reservoir characteristics are studied.Based on the research results of reservoir sandbody distribution characteristics and physical properties in the study area,the favorable area is optimized.Analysis shows that the Chang 6 oil layer in study area is generally 120.34 to135.5 meters and it can be divided into Chang 6¹,Chang 6²,Chang 6³ and Chang6⁴four subgroups oil layer.The structure of the study area inherited regional tectonic background which is similar to the flat terrain features with relatively flat tectonic setting.Each layer shows high east and low west monoclines of large scale.Furthermore,two small nose shaped uplifts are developed.The whole sedimentary environment is relatively stable,which belongs to the delta front subfacies deposition,and the sand bodies are mainly distributed from the NE to SW.Two kinds of sedimentary microfacies can be identified which are underwater distributary channel and inter distributary bay.The lithology of Chang 6 reservoir is mainly light grey,grey fine clastic feldspar sandstone or feldspar sandstone,and rare feldspathic sandstone.The diagenesis is intense.The sandstone reservoirs have undergone compaction,pressure dissolution,gaolinization,sericitization,authigenic mmineral filling,dissolution,metasomatism,recrystallization of clay minerals and other epigenesis.Occasionally,there are some unfilled microcracks.It eventually evolved into a low porosity and ultra-low permeability sandstone reservoir.The pore size of Chang 6 reservoir is mainly pore and pore type,and throat is mainly composed of middle throat and fine throat.The average porosity of the chang 6 reservoir is 9.28%,and the average permeability is 0.74×10^-3?m².Combining the characteristics of the reservoir properties,capillary pressure curves and parameters in the study area,the classification and evaluation criteria of the Chang 6 reservoir are established,and then Chang 6 reservoirs in the study area are divided into four types.At last,the favorable areas are optimized for each layer,which provides the basis for the discussion of the follow-up development plan.