Structural Performance Analysis And Optimization Of Wedge Packers

In the process of low permeability oilfield development,the fine stratified water injection technology can make every oil layer distribution reasonable and water injection symmetrical,thereby improving the efficiency of oil displacement and increasing oil recovery.But during the water injection process,due to the difference between the heterogeneity and water absorption capacity of the reservoir,the pressure difference between the layers is large and the creep deformation of the pipe string causes the sealing performance of the packer is poor and easy to fail,so that,the failure of the stratified water injection will affect the effective development of the oil field.The wedge packer used in the process of stratified water injection is restricted by the size of the vertebral body and the perfonnance of the packer,so that the sealing performance of the wedge packer can not be further improved,and the quality of the fine stratified water injection will be affected.In this paper,the wedge packer as the research object,through the analysis of the working principle of wedge packer failure,a new type of wedge packer is design by improvement of the structure of the wedge packer,because of the the contact stress of the wedge packer and casing is low,and the three-dimensional model of the wedge packer is established to verify the mechanism rationality of the wedge packer.The seal structure model of the wedge packer is established by the finite element analysis software,and the sealing performance of the improved wedge packer is compared and analyzed.the results show that the mechanical parameters such as maximum contact stress,average contact stress and contact length between the sealing wall and the wall of the wedge packer are all improved than unprotected rubber.The influence of the thickness of the vertebral body and the structure of the piston sleeve on the sealing perfornance of the wedge packer is analyzed by the finite element model of the sealed structure.The effects of different sealing parameters on the sealing performance of the wedge packer under diff-erent parameters were studied.The distributing disciplin of the contact stress and the change of contact length under different structural parameters were obtained.At the same time,the influence of factors such as Compression distance is studied.The parameters of the structure parameters of the sealant rubber and the protective rubber are optimized based on the response surface method.First,the maximum contact stress between the sealant rubber and the casing wall is taken as the experimental results.The structural parameters of the sealing rubber and the protective rubber are analyzed orthogonally,and the structural parameters with significant influence on the experimental results are obtained through the range analysis of the experimental results.Then,the response surface model is built to optimize the objectives and design variables in response to the design method of Box-Behnken by selecting the maximum contact stress as an optimization goal,selecting the structural parameters of the sealant rubber and the protective rubber as the design variables,selecting the structural parameters range of the sealant cylinder and the protective rubber cylinder as a constraint condition.The response surface model is validated by F test,coefficient of variation,multiple correlation coefficient,residual normal probability distribution and so on,and the feasibility of the model is evaluated.According to the regression model equation,the optimization module of Design-Expert 8 is used to optimize and analyze the structural parameters of the sealant rubber and the protective rubber in the setting range.Through the optimized the structural parameters of the sealant rubber and the protective rubber,the sealed structure model of the optimized parameters is established.Then,The mechanical parameters between the sealant cylinder and the casing wall before and after the optimization are compared and analyzed.In this paper,the sealing structure of wedge packer is improved,and the influence of different sealing structure parameters on the sealing performance of wedge packer is studied.At the same time,the structural parameters of sealing rubber and protective rubber cylinder are also studied.