某海上气井连续氮气气举作业61.5 h后, 发生连续油管断裂, 观察发现连续油管外壁腐蚀严重。通过宏观和微观分析、理化性能检验、X射线衍射和模拟试验, 对腐蚀油管进行了失效分析。结果表明, 气举作业所用氮气携带的O2和井内CO2共同作用造成了连续油管腐蚀破坏, 氧腐蚀是造成短时间内连续油管严重腐蚀的主要因素。针对此结论和现场工况, 采取除氧防腐蚀措施, 解决了现场作业中连续油管的腐蚀问题。

A coiled tubing in an offshore gas well cracked and suffered serious corrosion after nitrogen gas-lift operation for 61.5 h. The failure cause of the tubing was studied by macro and micro analysis, physical and chemical properties testing, X-ray energy spectrum analysis and stimulated corrosion test. The results showed that the combined effect of O2 carried by N2 and CO2 in the wet gas well corroded the coiled tubing. The O2 corrosion was the main reason of the corrosion of coiled tubing in short time. According to the results and the on-site conditions, measures to remove O2 was taken and the corrosion problem was resolved.