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| Analysis of Buckling Instability of Sinker Bar in Gas Well |
| Received:May 21, 2017 Revised:September 15, 2017 |
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| DOI：10.7643/ issn.1672-9242.2017.09.021 |
| KeyWord:sinker bar buckling leak metallographic analysis |
| Author | Institution |
| CAI Ke |
Research Institute of Tubular Goods of CNPC, Xi'an , China |
| LU Cai-hong |
Research Institute of Tubular Goods of CNPC, Xi'an , China |
| MA Xiao-fang |
Research Institute of Tubular Goods of CNPC, Xi'an , China |
| LI Xiao-long |
Research Institute of Tubular Goods of CNPC, Xi'an , China |
| SONG En-peng |
Research Institute of Tubular Goods of CNPC, Xi'an , China |
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| Abstract: |
| 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. |
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