Downhole O 2 corrosion during air-assisted steam injection for secondary or tertiary oil recovery

Abstract

Air-assisted steam injection is used as a secondary or tertiary oil recovery technology. During closing, downhole tubular goods are subject to corrosion in a mixed oxygen–steam–hot solution environment. This study investigates the influence of air injection pressure, temperature and Cl⁻ ion concentration in the injection water on the corrosion of P110 steel. Results show that high air injection pressure for increasing oil recovery ratio leads to the highly aggressive corrosion. The trend of corrosion rate and temperature in air-saturated injection water is a reversed ‘V’ curve. However, the high Cl⁻ concentration, which promotes the formation of large holes in the magnetite scale, greatly reduces corrosion. A suitable injection press that balances the oil recovery ratio and corrosion rate of oil tube, avoiding 170°C suitable for the highest corrosion rate, and periodic removing corrosion scales are necessary to inhibit further deterioration of downhole tubular goods.