油井管接箍失效原因分析

基于失效油井管接箍宏观分析的初步判断,采用扫描电镜微观分析、金相组织分析等方法,对失效的油井管接箍展开了系统分析。但是从EDS分析结果来看,腐蚀产物成分中含有C元素和O元素,该腐蚀区域位于井下166~176m,此处为套管气,湿度较大,具备发生腐蚀的条件,电化学测试,测其腐蚀电位、腐蚀电流及腐蚀速率,二者电位差为13mV,低于可以激发电偶腐蚀的阀值50mV,说明失效接箍和油管发生电偶腐蚀的概率极低。但是对工况进行分析发现,电缆存在漏电现象。造成局部带电,可以增加电偶腐蚀的阈值,故更容易发生电偶腐蚀。

Failure analysis of tubing coupling in oil well

Based on the preliminary judgment of the macroscopic analysis of the failed oil well pipe couplings,a systematic analysis of the failed oil well pipe couplings was carried out using SEM microanalysis and metallographic analysis. However,from the analysis results of EDS,the corrosion products contain C and O elements. The corrosion area is located 166-176 m downhole. Here,the casing gas has a relatively high humidity and has the conditions for corrosion to occur. The corrosion potential,corrosion current,and corrosion rate are 13 mV,which is lower than the threshold of 50 mV that can stimulate galvanic corrosion,indicating that the probability of galvanic corrosion of failed couplings and oil pipes is extremely low. However,the analysis of the working conditions found that the cable has a leakage phenomenon. As a result of local electrification,the threshold of galvanic corrosion can be increased,so galvanic corrosion is more likely to occur.