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采用宏观分析、化学成分分析、力学性能试验、金相检验、扫描电镜断口分析及能谱分析等手段对某规格为φ139.7 mm×10.54 mm的G105钻杆的刺穿原因进行了分析。结果表明:钻杆刺穿的实质是早期疲劳失效;蹩钻、跳钻等钻柱振动引起钻杆上产生的严重交变应力是导致钻杆失效的主要原因;钻井液中的溶解氧对钻杆外表面造成氧腐蚀并形成腐蚀坑,促进了疲劳裂纹的萌生;钻铤直接过渡到钻杆,截面变化突然,使应力集中加剧,也是导致钻杆发生疲劳失效的原因之一。建议在钻井液中添加除氧剂和缓蚀剂,并适当降低钻压,调整钻井参数,避免钻柱剧烈振动。
The causes of piercing of a G105 drill pipe with a diameter of φ139.7 mm × 10.54 mm were analyzed by macroscopic analysis, chemical composition analysis, mechanical property test, metallographic examination, scanning electron microscope fracture analysis and energy spectrum analysis. The results show that the essence of drill pipe piercing is early fatigue failure. The serious alternating stress caused by drill pipe vibration, such as lap drilling and jumping drill, is the main cause of drill pipe failure. The dissolved oxygen in drilling fluid affects drilling Oxygen corrosion and corrosion pits are formed on the outer surface of the rod, which promotes the initiation of fatigue cracks. The direct transition of the drill collar to the drill pipe causes a sudden change in cross-section and intensifies the stress concentration, which is also one of the causes of the fatigue failure of the drill rod. It is suggested to add oxygen scavenger and corrosion inhibitor into the drilling fluid, reduce WOB and adjust drilling parameters to avoid violent vibration of drill string.