N80钢防砂管腐蚀穿孔原因分析

Corrosion Causes Analysis of the N80 Steel Sand Control Tubing

为了分析西部某油田N80钢防砂管表面腐蚀穿孔及断裂的原因,对防砂管进行了宏观检查、壁厚测量、磁粉探伤、理化检验及扫描电镜(SEM)观察等综合分析。结果表明,该防砂管腐蚀穿孔的主要原因是基管(碳钢)和护管(不锈钢)浸泡在同一电解质(井下采出液)中,由于碳钢与不锈钢之间存在电位差,导致相互之间发生电偶腐蚀,使得电位较低的基管(碳钢)首先发生腐蚀,最终腐蚀穿孔而断裂。

In order to analyze the causes of corrosion perforation and fracture of N80 steel sand control pipe in an oilfield in western China, the sand control pipe was analyzed synthetically by appearance inspection, wall-thickness measurement,magnetic powder inspection, physicochemical inspection and scanning electron microscope（SEM） observation. The results show that the main cause of corrosion perforation of the sand prevention pipe was that when the base pipe（carbon steel） and the protecting pipe（stainless steel） were soaked in the same electrolyte（underground extraction liquid）, the galvanic corrosion occurs for the reason of potential difference, then lower potential base pipe（carbon steel） was preferred to corrosion, eventually lead to corrosion perforation and fracture.