高某气井加重杆屈曲失稳分析

目的分析某气井开展节流器投放作业时被高压天然气顶飞的加重杆的失效原因。方法采用外观检查、宏观分析、无损检测、螺纹检测、金相分析和受力计算等检测或分析方法进行了失效原因分析。结果加重杆本体金相组织无异常,但螺纹的螺距和齿宽均变窄,齿高变高,变形严重,其组织均有变形流线。通过应力计算和分析表明,失效的加重杆受到轴向压应力远大于杆体失稳的临界力。结论失效的主要原因是气井注醇作业未将井筒疏通,导致其下部井筒内压力过大,加重杆受到向上冲力和防喷器阻力叠加的轴向压应力超过了其杆体失稳的临界力,从而导致其严重变短变粗而屈曲失稳。同时加重杆受到的向上冲力也超过了防喷器阻力,因而冲破了防喷器的阻碍而飞出井口。

Analysis of Buckling Instability of Sinker Bar in Gas Well

Objective To analyze failure causes of sinker bar ejected by high pressure natural gas in distributing flow controller in a gas well. Methods The failure causes was analyzed by visual inspection, macroscopic analysis, non-destructive testing, thread detection, metallographic analysis, etc. Results The metallographic organization of the sinker bar had no abnormality, but the thread pitch and tooth width were narrowed, the tooth was higher, and the deformation was serious. Its organization had flow lines. Through stress calculation and analysis, the axial compressive stress of failed rod was greater than the critical force for instability of the rod. Conclusion The main reason of failure was that the wellbore was not cleaned, resulting in excessive pressure in the lower part of the wellbore, and the axial compressive stress superimposed by the upward force and the anti-blower resistance exceeded the critical force, and buckling happened due to serious shortening and thickening; at the same time, the upward momentum suffered by the sinker bar also exceeded the BOP resistance, and thus the rod broke through the BOP prevent obstacles and flew out of the wellhead.