Objectives To clarify the corrosion failure causes of N80 tubing in a production well of heavy oil fire flooding in Xinjiang oilfield,and to identify the main control factors and corrosion mechanism.Methods The service history and macroscopic corrosion morphology of the fire-drive production well tubing were analyzed.The chemical composition,metallographic structure and mechanical properties of the failed tubing were analyzed.The corrosion products were analyzed by SEM,EDS and XRD.Results The chemical composition and mechanical properties of the failed tubing were in line with the relevant standards,and the metallographic structure was normal.The oil pipe was mainly corroded locally,and the outer diameter of the oil pipe was reduced by 1.89 mm after only 1 year of service.The corrosion product layer has a thickness of 96 μm and is mainly composed of Fe2O3,FeCO3 and FeOOH.Conclusions CO2 corrosion and O2 corrosion have occurred in the failed tubing at high temperatures,and the synergistic effect of O2 and Cl-was the main cause leading to the development of local corrosion in the tubing.It is recommended that Al alloy sacrificial anode short sections be used for protection,and the research results provide a reference for the corrosion and protection of tubing string in fire-drive environment.
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