利用井下挂环的方法评估注多元热流体井筒油管的腐蚀行为。通过失重法、扫描电子显微镜、能谱分析仪、蚀坑3D形貌分析等方法研究了不同井身位置挂环的腐蚀速率和腐蚀产物膜特征。结果表明:随着井身深度增大,油管内环和外环的腐蚀速率均显著增大;由于油管内部和外部接触的腐蚀介质有所差异,内环的腐蚀速率远高于外环,但随着井身深度增大内环/外环腐蚀速率比逐渐减小;挂环腐蚀产物均由大量铁的氧化物和少量碳酸亚铁组成,呈多层结构,外环腐蚀产物的层状结构相比内环腐蚀产物更加复杂;在井身中上部,腐蚀主要受高温多元气相流体的氧化反应主导,而在井身下部主要由高温CO₂-O₂溶液的电化学腐蚀主导。

Downhole hanging ring method was used to evaluate the corrosion behavior of wellbore tubing injected with multi-thermal fluid. And the corrosion rate and corrosion product film characteristics of hanging rings at different wellbore positions were studied by weight loss method, scanning electron microscope, energy spectrum analyzer and 3D morphology analysis of corrosion pits. The results showed that the corrosion rates of the inner and outer rings increased significantly with the increase of wellbore depth. Due to the difference of corrosive media between the inside and outside of the tubing, the corrosion rate of the inner ring was much higher than that of the outer ring. But the ratio of corrosion rate between the inner ring and the outer ring decreased gradually with the increase of wellbore depth. The corrosion products on hanging rings with a multilayer structure were composed of a lot of iron oxides and a small amount of ferrous carbonate. And the layered structure of the corrosion products on the outer ring was relatively more complex compared to the corrosion products on the inner ring. In the middle and upper part of the wellbore, corrosion was mainly dominated by the oxidation reaction of high-temperature multi-gas-phase fluid, while in the lower part of the wellbore, it was mainly dominated by the electrochemical corrosion of high-temperature CO₂-O₂ solution.