| In the current oil and gas development process,the packer is one of the most important tools in the process of sub-stratified mining,fracturing,water injection and water shutting and so on.Compressed packer is one of the pressure capacity,simple principle,widely applicability packer structure.However,due to its sealing key component-rubber,has the nonlinear factors in material,geometry and deformation,the design theory especially the design of sealing pressure capacity is mainly based on empirical formula,and lacking accurate computing method,design theory and experimental basic.In this paper,based on the investigation of the existing structure,working conditions and common rubber materials,the calculation model of sealing pressure difference was established by means of theory and numerical simulation method,and with the same condition of visual experimental data,verifying the conformity rate of theoretical method and numerical simulation model,optimizing the factors which infect the calculate the accuracy.The research results of this paper provide a calculation method for the prediction of the differential pressure of the compression packer rubber.The main research contents and results are as follows:(1)Getting the important parameters describing the physical and mechanical properties of rubber,such as elastic modulus,Poisson's ratio and stress-strain parameters through experiment of mechanical properties of materials.Carrying out the friction coefficient test of rubber material,organic glass material and metal material,the experiments of mechanical properties and friction experiments provided reliable data for the calculation of the pressure difference of the rubber.(2)Using the space axisymmetric study methods,compression packer rubber stress axisymmetric model was established,deducing the mathematical relationship among the packer compression distance,sealing pressure difference and sitting load on setting and sealing pressure differential process.On the basis of the above analysis,three kinds of hydrogenated nitrile rubber materials were analyzed under different load conditions.The results showed that HNBR-01 and HNBR-02 were suitable to be used as the material of the compression packer rubber.(3)Based on the theory of fluid pressure penetration,the seal pressure numerical simulation model was set up,analyzed the variation law of the compression distance and the sealing pressure difference of the rubber under different load.The results showed that on the process of packer setting,the middle part and near the un-loading part of the rubber were firstly contact with the casing to form a sealing surface,and the numerical simulation method was more suitable for the nonlinear characteristics of rubber material.Taking the capacity of pressure difference and the difficulty of failure into account,HNBR-02 was recommended to be used for compression packer rubber.(4)Finished the experimental scheme including setting,sealing and failure and experimental device manufacturing,carried out the setting and seal pressure differential experiment of compression packer rubber.The experimental results showed that rubber compression distance had the nonlinear growth trend with the increase of setting load.Increasing the equivalent axial sealing load,rubber compression distance growth rate decreased.When the sealing load of the rubber was two times more than that of the minimum sealing load,sealing pressure capacity could be significantly improved by slight increase load.(5)Comparative analysis of visual experimental data and theoretical calculation and numerical simulation data,the results shown that the compression distance calculated coincidence rate of the three methods were more than 90%compared with the experiment values.The results obtained from the numerical simulation of the sealing pressure difference of super elasticity were between 15%-20%that was the smallest error among three methods.Based on the optimization of the HNBR-02 mesh type of hydrogenated nitrile rubber material,the calculation of sealing pressure difference in the error of about 8%under CAX4RH.So Choses the super-elastic numerical simulation method for the prediction of compression distance and the sealing pressure difference,meanwhile the rubber must use the CAX4RH mesh type.To sum up,this paper abandons the contact pressure as the standard of the sealing ability of the compression packer.The theoretical calculation and the numerical simulation model of elastic and hyperelastic are established.The accuracy of the three calculation model is verified by visual experiment,hyperelastic numerical simulation mode was chosen out and be optimized,5o as to improve the accuracy of the super-elastic numerical simulation model.The research results of this paper provide a study method for the prediction of structural design,compression distance and sealing pressure difference of compression packer rubber. |
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