Abstract
In order to investigate the corrosion behavior of N80 steel in production wellbores of oxygen-reduced air drive, the main corrosion control factors are analyzed based on gray relational analysis. Taking reservoir simulation results as indoor simulation parameters, the corrosion behavior in different production periods is studied by the dynamic weight loss method combined with metallographic microscopy, XRD, 3D morphology, and other related characterizations. The results show that oxygen content is most sensitive to the corrosion of production wellbores. The corrosion rate increases significantly under oxygen-containing conditions, and the corrosion rate at an oxygen content of 3% (0.3 MPa) is about 5 times higher than that without oxygen. At the initial stage of oil displacement, the corrosion is CO(2)-dominated localized corrosion, and the corrosion products are mainly compact FeCO(3.) With the prolongation of gas injection time, the wellbore is in a CO(2)/O(2) balanced environment, the corrosion changes into a combined action of the two, and the corrosion products are FeCO(3) and loose porous Fe(2)O(3). After continuous gas injection for 3 years, the production wellbore is in a high O(2) and low CO(2) environment, the dense FeCO(3) is destroyed, the corrosion pit develops horizontally, and the corrosion changes to O(2)-dominated comprehensive corrosion.