Abstract:Severe oxygen corrosion is one of the key factors that limit the advance of the air injection technology for EOR in the oil field. In this study, methods of weight loss, XRD analysis, EDS analysis and SEM analysis were used to clarify the corrosion law and protective measures of downhole string in air injection process. The experimental results indicate that oxygen corrosion rate increases with rising pressure, even at the atmospheric condition steels also suffer severe corrosion with the rate much larger than the industrial standard (0.076mm/a). There exist a critical temperature and a critical salinity at which the oxygen corrosion rate can reach the largest. In addition, increasing fluid flow rate is also conducive to oxygen corrosion. The main elements of corrosion products are γ-FeO(OH), β-FeO(OH), Fe3O4 and α-FeO(OH). The structure of corrosion film is loose, therefore has little protective effect on steel matrix. The validity of the anti-oxygen corrosion measures has been verified. Various anti-corrosion measures should be considered to effectively control the oxygen corrosion of downhole string, including selecting high-quality steel type, the use of grease to treat the steel surface, pH adjustment, and filling or injecting corrosion inhibitor.