某井改良型13Cr特殊螺纹接头油管腐蚀原因分析

Cause Analysis on Corrosion of Modified 13Cr Tubing with Premium Connection

针对某天然气井油管腐蚀严重的问题,将起出的油管螺纹接头进行了宏观检查,对不同井段油管腐蚀分布规律进行了统计分析,对油管的化学成分和腐蚀产物进行了试验分析。分析认为油管接头部位腐蚀集中与接头转矩台肩部位内倒角结构尺寸、内倒角部位加工精度有关;油管外螺纹接头端面腐蚀原因与油管在井下受力状况有关;导致改良型13Cr油管腐蚀的原因不仅与天然气中CO2、凝析水等腐蚀介质有关,而且与井下温度有关。

An investigation on corrosion cause of tubing string in one well is given in this paper,and the tubing connections used in the well were inspected by vision.Statistics of distribution regulation was made for tubing corrosion,and tests were done in chemical component and corrosion product.It was shown that corrosion concentration on joint is not only related to inner bevel structure dimension,but also related to roughness on inner bevel.It was proved that tubing corrosion on torque shoulder concerns with load born on tubing string.The corrosion cause of modified13 Cr tubing had a bearing on CO2,condensate water and temperature in the well.