某井钻杆管体断裂失效原因分析

Fracture analysis of drilling pipe

某井钻进过程中,钻杆发生断裂事故。对钻杆断裂事故进行了深入调查研究,分析了断裂钻杆样品,对断口形貌、几何参数、理化性能、金相组织和腐蚀产物能谱分析等进行了试验分析。试验分析结果表明,钻杆的理化性能均满足API SPEC 5DP要求及用户要求,钻杆断裂机理为早期腐蚀疲劳,钻杆过渡区内表面的腐蚀和应力集中是失效事故的主要原因,造斜点处的交变弯曲应力促进疲劳腐蚀的快速发展。

A fracture accident of drill pipe took place in one oil field. In order to know the cause of fracture of drill pipe, an investigation on the accident was introduced. Two fracture pipe samples were analyzed. Analyzed fracture morphology, geometric parameters, physical and chemical properties, microstructure and corrosion products. The test results show that, the physicochemical properties of drilling pipe meted API SPEC 5 DP requirements and user requirements. The main mechanisation of fracture is corrosion fatigue of early phase. The main causes of failure accidents is corrosion and stress concentration on the surface of drill pipe transition zone are. The alternating bending stress at the inclination point promotes the rapid development of fatigue corrosion.