一种石油钻杆的腐蚀机理

摘要

A high temperature and pressure autoclave was used to simulate the drill pipe corrosion in situ field environment of Tarim oil field. The corrosion products and corrosion mechanisms of 8135 drill pipe working in lignosulfonate mud were studied. The corrosion product film on the outside of the drill pipe was analyzed by XRD and SEM. The results showed that localized oxidation corrosion occurred on S135 drill pipe, the features were the ulcerlike corrosion, localized contiguous corrosion and pit corrosion. The main corrosion products were orthorhombic crystal system＇s allcharite. The corrosion took place while the drill pipe standed on the derrick, where moisture in the mud cake clinging to the outside of drill pipe volatilized to the air and produced iron hematite, barite, bentonite powders and calcium powders. Three kinds of interrelated localized corrosion induding differential oxygen concentration corrosion, bimetallic corrosion and crevice corrosion oecured.%采用高温高压釜，模拟研究了塔里木油田现场环境所用聚磺体系钻井液对S135钻杆的腐蚀行为及腐蚀机理。通过对表面黏附有泥饼的挂片进行X射线衍射（XRD）和扫描电镜（SEM）分析，对腐蚀形貌和腐蚀产物进行了研究。结果表明，S135钻杆发生了局部氧腐蚀，特征为溃疡状腐蚀、连片局部腐蚀和深坑腐蚀，腐蚀产物主要是正交（斜方）晶系的针铁矿。钻杆腐蚀的主要原因是起钻时未刮泥浆，粘附在钻杆外壁的泥浆膜在空气中水分挥发过程和形成泥饼壳后便留下铁矿粉、重晶石、土粉、碳酸钙粉等作为骨架的固相物，称为垢层。垢层与钻杆表面接触，产生三种相互关联的局部腐蚀，即供氧差异微电池腐蚀、电偶腐蚀和缝隙腐蚀。