L80油管螺纹接头腐蚀原因分析

摘要

某井L80油管下井投入使用仅6个月即发生螺纹接头腐蚀失效.采用宏观分析、金相分析、化学成分分析、腐蚀表面微观形貌及腐蚀产物分析等方法对现场发生腐蚀失效的管样进行了检验和分析;通过高温、高压工况模拟腐蚀试验, 对油管材料的腐蚀行为进行了研究分析.结果表明:油管螺纹接头表面的腐蚀产物主要为FeCO3, 腐蚀局部集中主要是由于油管在下井时, 螺纹部位存在粘扣现象, 从而导致螺纹接头的密封性能下降, 高矿化度地层水及CO2等腐蚀介质渗入螺纹连接处, 形成了缝隙腐蚀.%Corrosion failure occurred to an L80 tube threaded joint in a well only after six months of use.Means such as macroscopic analysis, metallographic analysis, chemical composition analysis, and corrosion surface micro-morphology and corrosion product analysis were used to test and analyze the corrosion tube sample in the field.The corrosion behavior of the tube material was studied by high temperature and high pressure working condition simulated corrosion test.The results show that the corrosion products on the surface of the tube threaded joint were mainly FeCO3.The local concentration of corrosion was mainly due to the thread gluing phenomenon of the tube thread part when it went down the well, which resulted in a decrease in sealing performance of the threaded joint.So high salinity formation water and corrosive medium such as CO2 infiltrated into the threaded joint and crevice corrosion happened.