Pitting Corrosion of S13Cr Tubing in a Gas Field: A Failure Case and Corrosion Mechanism Analysis

This work investigated the pitting failure mechanism of S13Cr tubing in a gas well resulting from multiple gas lifts. The causes of pitting corrosion through the use of numerical simulations (CFD) were determined. Electrochemical noise technique was used to explore the process of pitting corrosion. Results show that the chemical elements, inclusions, metallographic structures, and strength of S13Cr tubing meet standard requirements. Scanning electron microscopy, energy-dispersive spectroscopy and X-ray photoelectron spectroscopy were used to analyze the compositions of corrosion products, which mainly consist of FeCO 3 , Fe 2 O 3 , FeOOH, Cr 2 O 3 , and Cr(OH) 3 . Numerical simulations show that a liquid film is formed in the local well section of the inner wall during gas lift. Electrochemical noise revealed a linear decrease in potential noise and a linear increase in current noise, indicating that the adsorption of Cl - on the electrode surface erodes the passivation film. Current and potential transient peaks began to appear and increase, indicating the development of pitting erosion toward a steady state. In the actual production process, S13Cr tubes lead to crack initiation and expansion due to the coupling of mechanical–chemical effects of Cl − , CO 2 , and O 2 .