通过理化性能检测、组织分析、腐蚀形貌、产物膜分析、流体和冲刷腐蚀数值模拟等手段,并结合现场服役工况,系统分析了某油田20号钢弯头短期内3次腐蚀穿孔的原因。结果表明:CO₂吞吐过程导致弯头部位出现CO₂腐蚀,生成的腐蚀产物膜疏松多孔,同时介质中固体颗粒的存在导致弯头外弧侧出现冲刷腐蚀。在CO₂腐蚀和冲刷腐蚀的共同作用下,弯头外弧侧FeCO₃产物膜破坏,金属基体裸露,外弧侧壁厚迅速减薄最终发生穿孔。最后,给出了避免或减缓此类弯头失效的建议。

On the basis of the service environment, the reasons of 20^# elbow 3 times failure in a short period were investigated by means of physical and chemical property testing, microstructure analysis, corrosion scale analysis, flow rate and erosion corrosion simulated results. The results indicated that CO₂ corrosion occurred at the elbow during the process of CO₂ huffing and puffing, and the loose and porous FeCO₃ corrosion scale formed. Meanwhile, the solid particles in the medium caused erosion corrosion on the outer arc side of the elbow. Under the synergistic effect of CO₂ corrosion and erosion corrosion, the FeCO₃ scale was destroyed, and metal was exposed on the outer arc side of the elbow, resulting in a rapid thinning of the outer arc sidewall and finally perforation. Finally, suggestions were given to avoid or slow down the rapid failure of such elbows.