Corrosion Behavior of Well Tube Steels for CO₂ Flooding Injection and Production Wells

The CO₂ corrosion resistance properties of four kinds of tubing materials N80, P110, 3Cr and 5Cr in fluid were studied using an autoclave. The morphology and components of corrosion products were studied by SEM, EDS and XPS. The results showed that the corrosion rates of those four kinds of materials increased first and then decreased as temperature increased, and the peak values of the corrosion rates all occurred in medium temperature zone. For N80, P110 and 5Cr, the peak value of the corrosion rates occurred at 90℃. The most serious corrosion happened at 80℃ for 3Cr. The corrosion type of the materials was uniform corrosion, and localized corrosion was not found. The major component of corrosion products was FeCO₃. The components of corrosion products with multilayer structure on 3Cr and 5Cr were FeCO₃ and amorphous compound Cr(OH)₃. The films of corrosion products of N80 and P110 were fine, compact and uiform on the surface, so the corrosion rates were low. The films of corrosion products on 3Cr and 5Cr were uneven and easy to drop, so the corrosion rates were relatively high.