Numerical Analysis And Experimental Study On Residual Stress Of Solid Expandable Tubular Under Different Working Conditions

With the increasingly complex drilling problems faced by oil and gas well exploitation,the solid expandable tubular technology,which can solve the problem of well diameter limited,has developed prosperously.After the expansion operation,the tubular inevitably exists a high level of residual stress,which will have adverse impacts on the service of solid expandable tubular.In view of this phenomenon,through the methods of test and finite element simulation,the distribution characteristics of residual stress of expansion pipe under multiple working conditions are studied,and the influence law of residual stress on the performance of expansion pipe is proved,which has certain engineering application value for the design and construction technology of solid expandable tubular.Firstly,the indoor expansion tests of two specifications of solid expandable tubular are carried out,the strain release coefficient of blind-hole method is modified by specific deformation energy of blind-hole edge,the plastic correction formula suitable for expansion tubular is proposed,and the circumferential and axial residual stresses on the outer wall of expandable tubular after expansion are obtained.The finite element simulation of expansion process is carried out in combination with the field conditions,and the error is less than 15% compared with the test results,which verifies the reliability of the finite element method for residual stress of expandable tubular.The research expands the application scope of the blind-hole method of the residual stress measurement,and determines a simple and fast test method.Then,the nonlinear expansion process of the expandable tubular is simplified as a rigid-flexible contact problem.The expansion process of the expandable tubular under different working conditions is simulated based on the finite element method.The effects of the frictions coefficient between tubular and mandrel,the half cone angles,chamfer radiused and expansion rates of the mandrel,as well as the initial geometric defects of the expandable tubular on the distribution of axial residual stress,circumferential residual stress and radial residual stress of the expandable tubular after expansion are analyzed respectively.The main factors affecting the magnitude and spatial distribution of residual stress in the range of actual working conditions are clarified.Finally,based on the existing research,the geometric model of the expansion tubular is extracted,the influence of residual stress on the collapse resistance performance of the expansion tubular is studied,and the collapse resistance strength of Φ194mm expandable tubular with residual stress is obtained.Through the analysis of the variation of residual stress distribution,the main reason for the spring-back of expansion end section tubular is obtained.On this basis,a new type of mandrel structure which can improve the shrinkage is proposed.