Study On Microscopic Pore Throat Characteristics Of Typical Diagenetic Facies In Chang 6 Reservoir In Tiebiancheng Area,Jiyuan Oilfield

The Chang 6 reservoir in Tiebiancheng area of Ordos Basin is a typical sandstone reservoir with low porosity and low permeability.The difference of reservoir microstructure is the typical characteristic of this kind of reservoir.The microstructural characteristics of the reservoir are the important factors affecting the percolation characteristics and the oil and gas recovery of the reservoir,and the difference of the microscopic pore throat structure is the important attribute of the microscopic structure characteristics of the reservoir.The sedimentation and diagenesis are the key factors for the difference of pore throat structure.Therefore,based on the basic geological background of the reservoir,the method of combining the experimental test data with the oilfield production data is adopted.The microcosmic characteristics of reservoirs and their relationship with the ecological data of oil fields are systematically analyzed to provide theoretical reference for improving the understanding of the microscopic characteristics of Chang 6 reservoir and optimizing the evaluation and development of low porosity and ultra-low permeability sandstone reservoirs in Tiebiancheng area.(1)A set of delta front and plain facies sand bodies have been deposited in Tiebian City area.Chang 6 reservoir can be divided into three sub-layers: Chang 61,Chang 62 and Chang 63.The main lithology is feldspathic sandstone and a small amount of lithic feldspar sandstone with fine granularity.Sorting is better,grinding round to the main sub-edge shape.(2)the target layer in the study area experienced complex diagenetic evolution process,which was in the late stage A of the middle diagenesis,and partly entered the early stage B of the middle diagenesis.The pore types were mainly intergranular pore and dissolved pore.According to the clay mineral content and the main pore assemblages,Chang 6 can be divided into six diagenetic facies,namely,chlorite cementation and residual intergranular pore facies,kaolinite cementation and residual intergranular pore facies,chlorite cementation and dissolved pore facies,respectively.Kaolinite cementation-dissolved pore phase,Illite cementation-dissolved pore phase,carbonate cementation phase.(3)based on the comprehensive analysis of various experiments,among them,chlorite cement-residual intergranular pore reservoir has good physical properties,intergranular pore development,large pore throat radius,high pore coordination number and good connectivity,and high movable fluid saturation.Oil / water two-phase flooding has low degree of interference,strong percolation ability,high oil displacement efficiency,worst carbonate cementation dense facies,low reservoir porosity and permeability,poor overall performance of pore structure,large amount of cementation and filling of pores,The pore throat radius is small,the connectivity is poor,the movable fluid saturation is low,the disturbance degree of oil-water two-phase displacement is large,the displacement efficiency is low,and the reservoir is basically ineffective in the study area.(4)different diagenetic facies reservoirs have different production performance.The daily oil and liquid produced by chlorite cementation and intergranular pore facies are the highest,the water content is lower,the stable production period is long,and the daily oil and liquid production of kaolinite cementation-dissolved pore facies is higher and the output is more stable.Illite cementation-dissolved pore phase Illite cementation and dissolved pore tuffaceous dissolved pore reservoir have lower daily oil and liquid yield,higher water cut,shorter stable production time and greater difficulty in development.