Corrosion Rate Prediction Model of Pipe Column of Water Injection Well in an Oilfield

Uniform corrosion immersion tests were conducted on 3Cr steel and 13Cr steel for pipe column of water injection well in an oilfield under conditions of ground-based artificial water injection (with dissolved oxygen) and self-contained closed-loop water injection (without dissolved oxygen). The influence of CO₂ partial pressure and dissolved oxygen content on the corrosion rate was analyzed. Based on the existing relationships between CO₂ partial pressure, dissolved oxygen content, H₂S partial pressure, temperature, flow rate, Cl⁻ content and corrosion rate, the model parameters were fitted by multiple linear regression, and the corrosion rate prediction model was established and verified through experiments. The results show that under the condition of ground-based artificial water injection, the uniform corrosion rate of 3Cr steel increased with the increase of CO₂ partial pressure and the decrease of dissolved oxygen content, and that of 13Cr steel changed very little. Under the condition of self-contained closed-loop water injection, the uniform corrosion rates of both steels increased with the increase of CO₂ partial pressure. The average absolute relative errors between the predicted corrosion rates of 3Cr steel and 13Cr steel and the test results were 24.44% and 8.13%, respectively. The prediction results of 13Cr steel obtained with the model had relatively high accuracy, showing that the established model could accurately predicate the corrosion rates of 13Cr steel pipe column of water injection well.