Analysis Of Collapsing Strength And Residual Stress Of Expansion Casing

Expansion casing drilling technology is an important emerging technology in recent years, and has been listed as the National 863 Project in 2006. This article focused on the key technologies in expansion casing which were residual stress and collapsing strength, and they demonstrated the necessity and urgent needing of studying in casing design and applications on engineering.Firstly analyzed all kinds of factors which impacted on the expansion casing collapsing strength, analyzed qualitatively and quantitatively these factors containing uneven wall thickness, the ellipticity, as well as non-uniform geometric deformation phenomenon, residual stress and other factors impacting on collapsing strength with ANSYS, the results revealed the law that the factors impacted on collapsing strength, and had great significance for guiding design, construction and selecting materials of expansion casing; The ideal casing collapsing strength of theoretical formula was amended and improved, greatly improved the accuracy of calculation formula.The collapsing strength of casing has a closely relationship to mechanical properties target. The mechanical properties target was analyzed by tube material and tube mechanical performance tests. In the tube material experiments, tested the minimum yield strength, elongation and other important performance parameters of expansion casing before and after, verified the feasibility of physical method to enhance the casing strength, identified that there was no difference between circumferential and axial minimum yield strength target when casing was expanded on ambient temperature, and made quantitative analysis which was basis for tube trial. In the tube experiments, tested the vertical and horizontal direction elastic modulus and anti-pressure inside and outside, it showed that the expansion casing could not only improve anti-pressure inside and collapsing capacity, but also increase the diameter of casing, improved the capacity of path.The residual stress in expansion casing is one of important factors affecting its collapse and pressure resistance. The residual stress in expansion casing which the specifications is J55 and K55 is tested by the hole drilling method, the testing results were amended with relieved strain coefficients grading method, the size and direction of residual stress in expansion casing were obtained; through comparing these testing results with simulations, because the errors met the requirement of engineering, so the results showed that the hole drilling method was convenient, fast, accurate, effective.The expansion process of expansion casing was very complex, and belonged to a rigid-flexible body contacting problem, existed friction, was a highly nonlinear behavior, so was simulated by ANSYS. Simulated and analyzed mainly the residual stress (effective stress after expansion) and axial displacement, to provide theoretical data for determine reasonably the friction between piston and casing, as well as the design of inflated bodies. At last simulated the dynamic process which residual stress formatted by using the finite element software DEFORM, and also to provide a more effective and simple platform for studying the expansion casing key technologies.