Research on the Corrosion of J55 Steel Due to Oxygen-Reducing Air Flooding in Low-Permeability Reservoirs

Oxygen-reducing air flooding is a low-permeability reservoir recovery technology with safety and low-cost advantages. However, in the process of air injection and drive, carbon in the air is oxidized through the crude oil reservoir to generate CO2, and this can cause serious corrosion in the recovery well. In this study, experiments on the corrosion of J55 tubular steel in a fluid environment with coexisting O2 and CO2 in an autoclave are presented. In particular, a weight loss method and a 3D morphometer were used to determine the average and the local corrosion rate. The corrosion surface morphology and composition were also measured by means of scanning electron microscopy (SEM) and an X-ray diffractometer (XRD). The corrosion pattern and morphological characteristics of J55 steel were analyzed in the O2/CO2 environment for different degrees of oxygen-reduction. As made evident by the experimental results, the corrosion products were mainly ferrous carbonate and iron oxide. In general, air injection increases the degree of oxygen reduction, from oxygen corrosion characteristics to CO2 corrosion-based characteristics. As a result, the corrosion product film becomes denser, and the corrosion rate is lower.