Study On Sealing Reliability Of Packer Rubber For High Pressure Fracturing

Under the complicated working conditions of oil and gas wells,the reliability of the Packer rubber is affected by high pressure environment or its own factors.It is difficult to locate the reliability of packer rubber accurately when the theoretical analysis is not clear.Therefore,it is very meaningful to carry out the mechanical analysis of the deformation of each stage of packer rubber,determine the sensitivity of the factors affecting the seal,and give the reliability model which can select the reliability safety factor.From the point of view of seal and failure form and reason of Packer,the sealing mechanism of the key component packer rubber under the action of hydraulic pressure is analyzed,and the failure mechanism of micro-roughness wear leakage and macro-shear failure is established.This paper analyzes the different deformation characteristics in the free deformation stage,the restrained deformation stage and the stable deformation stage in the sealing process of packer rubber,and establishes the corresponding numerical analysis model,especially the free deformation stage.According to the theory of nonlinear continuum mechanics,the mathematical equation of the finite free deformation stage of packer rubber is derived,and the numerical solution model is constructed.The model is carried out by MATLAB.Numerical analysis is made to analyze the influence of different parameters on the displacement and deformation in the free deformation stage of packer rubber.Aiming at the unreliable sealing problem of packer rubber involving non-normal distribution variable in engineering practice,two numerical methods of mechanical reliability sensitivity analysis are proposed on the basis of mechanical reliability model of packer rubber.The structural parameters,material parameters,working pressure difference and load distribution of packer rubber with non-normal distribution are analyzed.The reliability and sensitivity calculation results of the sealing performance of the rubber cylinder under the influence of machine uncertainty are presented.The reliability safety factor model of static strength of packer rubber with stress-strength obeying normal distribution is established.The calculation method and process of parameters involved in reliability safety factor model are given.The value standard of reliability safety factor at different levels affecting the parameters of packer rubber with stress and strength obeying normal distribution is calculated and determined.It provides the basis for the reliability design requirement of packer rubber for high pressure fracturing.