Study On Repairing Technology Of Thin-wall Tube Of Shallow Casing

Conventional casing subsidy technology has the problem of the small diameter and a remarkable impact on the path after the completion of casing repair.Studies have shown that the application of thin-wall subsidy tube for casing repair can effectively solve the path problem.Under this researching background,based on the analysis of the relevant literatures on the casing subsidy technology,and the research status of the casing and subsidy technology in domestic and foreign oil fields combined with the actual restoration of the thermal loss of the Shengli Oilfield,this paper aims at the repairing process of thin-walled large-diameter subsidy tube of shallow casing.The expansion mechanism of the expansion tube is not clear under the condition of large expansion rate with no effect on the diameter,either can it provide the theoretical basis for the reasonable design and selection of the repairing tube.In the course of the experiment,the use of 304 and 316 stainless steel filler tube shows a phenomenon of buckling failure,because the material is not appropriate,the structure is unreasonable.Therefore,it is important to find the appropriate shallow casing repairing material and the appropriate parameters in designing the expansion subsidy tube and its sealing structure.A thin-walled subsidy tube for shallow casing repair was designed.On the basis of analyzing the performance requirements and market research of the subsidy pipe,a special steel pipe was selected as the subsidy pipe material.On the basis of the basic equation of the space axisymmetric problem,the mathematical expression of the mechanical parameters in the process of expansion is deduced according to the boundary condition and the yield rule.The two-dimensional finite element model of "expansion cone-subsidy tube-casing" is established.The finite element analysis of the plastic deformation of the subsidy tube under the action of the expansion cone is carried out.The driving force and the contact pressure of the expansion cone are obtained with the change of displacement of the expansion cone.The influence of the friction coefficient between the expansion cone and the subsidy tube on the expansion process is studied.The mechanical behavior of the expansion process under different expansion taper angles is studied.By comparing the stress and driving force of the subsidy tube under different conditions,the optimum expansion cone angle suitable for casing subsidy is determined.The finite element analysis of the thread interface of the subsidy tube is carried out.The three-dimensional finite element model of buckling analysis of subsidy tube is established in ANSYS Workbench.The buckling failure of subsidy tube is obtained by solving the buckling mode and the critical buckling load value of the subsidy tube under the axial load.By comparing the magnitude of the first order buckling load and the driving force of the expansion cone,the safety length of the buckling deformation of the subsidy tube is determined.The design of the sealing structure of the subsidy tube was completed,and the sealing pressure of the sealing material with different sealing materials was calculated by the finite element method.According to the result,it was judged whether it meets the pressure requirement of 12 MPa.