油井管特殊螺纹齿表面应力腐蚀行为仿真研究

Simulation Study on Stress Corrosion Behavior of Special Thread Teeth Surface of Oil Well Tubing

随着高温高压高产油田的勘探开发,油井管柱面临越来越恶劣的井筒环境,其螺纹接头腐蚀失效已经成为制约油气田高效开采的主要原因之一。为此,通过COMSOL Multiphysics软件建立了油井管螺纹齿的力学-电化学有限元模型,研究了不同外部载荷下油井管螺纹各个部位的应力分布与腐蚀规律。研究结果表明:油井管螺纹齿各个部位的应力分布大小与其腐蚀程度呈正相关,即接触应力越大,螺纹腐蚀情况越严重;接头螺纹在齿槽与承载面过渡处的应力最为集中,腐蚀情况最为严重,塑性变形会导致阳极腐蚀电流密度急剧增大,造成严重的腐蚀行为。研究结果可为油井管柱接头螺纹腐蚀失效机理研究提供新的思路,也为解决恶劣工况条件下井筒完整性问题提供理论依据和解决途径。

With the exploration and development of high-temperature,high-pressure and high-yield oilfields,oil well tubing is facing increasingly harsh wellbore environments,and the corrosion failure of its threaded coupling has become one of the main reasons restricting the efficient exploitation of oil and gas fields.In this paper,a mechanical-electrochemical finite element model for thread teeth of oil well tubing was built using COMSOL Multiphysics,and the model was used to study the stress distribution and corrosion laws of various parts of threads of oil well tubing under different external loads.The results show that the stress distribution of various parts of the oil well tubing thread teeth is positively correlated with the degree of corrosion,that is,the greater the contact stress,the more severe the thread corrosion is.The stress of the joint thread is most concentrated at the transition between the gullet and the bearing surface,where the corrosion is most severe.Plastic deformation can cause a sharp increase in anode corrosion current density,resulting in severe corrosion behavior.The study results provide new ideas for the study of the corrosion failure mechanism of oil well tubing joint thread,and also provide theoretical basis and solutions for solving wellbore integrity problems under harsh working conditions.