Study On Productivity Of Fractured Horizontal Wells In Anisotropic Tight Gas Reservoirs

As conventional oil and gas resources enter the later stage of development,unconventional oil and gas has gradually become the focus of development.Large and ultra-large tight gas fields are constantly emerging in the Ordos Basin,Sichuan Basin and other places,and tight gas has an increasing share in the national energy structure.Due to the characteristics of low porosity and low permeability in tight gas reservoirs,fracturing horizontal well technology is generally used for development.Among them,there are factors such as anisotropy,stress sensitivity,and starting pressure gradient.Horizontal well productivity is of great significance for the development of tight gas.In this paper,for the anisotropic tight gas reservoir,the stress sensitivity of the reservoir and the starting pressure gradient experimental research are started.By changing the effective stress of the core to test the permeability of the core under different stresses,the expression formula of stress sensitivity of the reservoir is fitted.The low-velocity flow experiment is carried out according to the "pressure differenceflow rate" method,and the starting pressure gradient data of the test core is calculated according to the fitting of the flow velocity and the pressure square difference.The experimental study of the two reservoir cores laid the foundation for the derivation and establishment of the productivity model.Then according to the flow law of the development of horizontal wells in tight gas reservoirs,the whole flow process is divided into two flow stages and three flow resistance zones.Flow resistance is obtained separately,and a basic model of single fracture productivity is established.Reservoir stress-sensitive productivity model and productivity model considering both reservoir stress sensitivity and starting pressure gradient.Then,the equivalent well diameter model is used to consider the inter-fracture interference of fracturing horizontal wells,and the single fracture model is converted into the overall productivity model of fracturing horizontal wells.In this way,through Visual Studio 2019 platform,using C # language for programming design,complete anisotropic tight gas reservoir fracturing horizontal well productivity evaluation software,and complete software testing through example calculation.Finally,eight parameters commonly used in the model are selected to analyze the influencing factors of the model.From the experimental study,it was found that the tested cores all have the phenomenon of stress sensitivity and starting pressure gradient.It is thought that the reservoir in the study area is affected by the stress sensitivity and starting pressure gradient,and the reservoir stress sensitivity is fitted by the experimental data.The general expression.Considering the effect of reservoir anisotropy through coordinate transformation,and fitting data from experimental research,a basic model of fracturing horizontal well productivity,a productivity model that considers reservoir stresssensitive productivity,and a reservoir are also considered based on tight gas flow characteristics The productivity model of stress sensitivity and starting pressure gradient,and the conversion of single fracture production to horizontal well production through the equivalent well diameter model.Completed the design of the productivity evaluation software,and was sensitive to the production pressure difference,reservoir permeability,fracture half-length,number of fractures,horizontal well length,angle between the horizontal well and the main permeability direction,stress sensitivity and starting pressure Eight gradient parameters were analyzed for influencing factors.