| Sandstone reservoirs of Funing Formation in W Oilfield of Gaoyou Depression,Subei Basin,are influenced by sedimentary environment.Sand bodies are overlapped vertically.The physical properties of target strata are poor,pore structure is complex,and affected by mud and lime.It is more difficult to model reservoir physical properties.The non-Archie phenomenon in saturation relationship is obvious,which affects the calculation accuracy of reservoir parameters.In addition,poor reservoir physical properties lead to low natural productivity,which basically requires reservoir fracturing transformation before production.At present,there is no mature method to predict the productivity of low permeability reservoirs after fracturing.Various problems greatly restrict the role of logging interpretation,and also bring troubles to engineering.In order to improve the accuracy of low permeability reservoir parameters in the study area,predict reservoir productivity after reservoir modification for engineering measures,and play the role of logging interpretation,this paper carries out the research of logging evaluation technology for low permeability reservoirs in Funing Formation of W Oilfield,based on rock physics experimental data,taking logging curve data as the main means,combining with geological characteristics of target area,oil testing and production situation and engineering measures parameters.Research.Firstly,the standardization of logging curves is carried out in the study area,and the standardized corresponding data tables are established by combining histogram with trend surface,thus eliminating the errors caused by different series of logging tools.At the same time,through core data,mud logging description and logging data,the relationship between lithology,physical property,electrical property,oil-bearing property and "four characteristics" of the studied area is systematically analyzed,and the basic characteristics of reservoirs are understood.Secondly,on the basis of petrophysics,the models of porosity,permeability,lime content and shale content with better applicability are established while the influencing factors are analyzed in reservoir parameters.In the traditional experiment of low permeability reservoir,capillary self-priming experiment is designed to better establish saturation model for low permeability reservoir.In addition,considering the influence of porosity,the dynamic-static conversion relationship of Poisson's ratio can be well obtained,and the brittleness index of the formation can be accurately calculated,which provides technical support for evaluating the compressibility of the formation.Then,according to the production data of oil testing and single well,the interpretation chart and interpretation standard of conventional fluid properties and post-fracturing fluid properties are established by using acoustic time difference,deep induction resistivity and natural gamma curve.Reservoir classification is focused on fractured reservoirs.Considering that there are many joint tests,normal reservoirs and fractured reservoirs are defined as reservoir I,and fractured reservoirs are defined as oil-water reservoirs.The reservoir of the same layer is defined as reservoir II,and the reservoir without productivity after fracturing is defined as reservoir III,which also provides preliminary judgment for the precondition of Engineering measures.Finally,the influence of logging curve characteristics,reservoir quality parameters,brittleness index and fracturing operation parameters on productivity is studied.It is considered that natural gamma ray,acoustic time difference,deep resistivity,brittleness index and actual construction pressure have a good relationship with productivity grading in W oilfield.Fisher discriminant method is used to establish a model for grading,and the coincidence rate is 80%.The treatment effect can meet the production needs. |
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