Corrosion Behavior of Steam Injection Pipeline in CO2/O2/SO2 Environment

In order to reveal the corrosion behavior and mechanical properties of 45# steel and 3Cr steel in the high temperature and pressure CO2/O2/SO2 system, and provide theoretical support for the safe operation of steam injection pipelines in Xinjiang Oilfield. Based on the on-site operating conditions of the steam injection pipeline, combined with high temperature autoclave, combined with scanning electron microscope, 3D microscope, X-ray diffractometer (XRD) and other means, weight loss test, product characterization and tensile test are carried out. With the increase of temperature (100-250 ℃), the corrosion rate of 45# steel and 3Cr steel shows a decreasing trend; with the increase of O2 content (0-3mol%), the corrosion of 45# steel and 3Cr steel rate first increases and then decreases, and the corrosion is inhibited when the O2 content is 2mol%-3mol%. The XRD test results show that the corrosion products of 45# steel in the CO2/O2/SO2 system mainly include FeSO4·H2O, FeCO3, Fe2O3, and the corrosion products of 3Cr steel mainly include Cr2O3, FeSO4·H2O, FeCO3, and Fe2O3. The 3D microscope results show that 45# there are obvious local corrosion defects on the surface of the steel substrate, and 3Cr steel does not appear local corrosion; the mechanical properties show that the tensile strength of 45# steel after corrosion is reduced by 1.36%, the elongation is reduced by 6.85%, and the tensile strength of 3Cr steel after corrosion Reduced by 0.39%, elongation reduced by 21.34%. In the high temperature and pressure CO2/O2/SO2 environment, SO2 dominates the corrosion process; the corrosion product film is dense at high temperature (100-250 ℃), which inhibits corrosion; O2 participates in the cathodic reaction, and in the low concentration of oxygen (0-2mol%), the corrosion product film is destroyed to promote corrosion. When high concentration oxygen (2mol%-3mol%), the steel matrix is passivated to inhibit corrosion; after corrosion, the mechanical properties of the steel are degraded, and corrosion has a greater impact on the elongation of the steel. The tensile strength is less affected. © 2022, Chongqing Wujiu Periodicals Press. All rights reserved.