Evaluation and application of corrosion inhibitors for production wells in the CCUS demonstration area of Xinjiang Oilfield

Objective In order to solve the problem of efficient and low-cost corrosion protection of the wellbore in carbon capture, utilization and storage (CCUS) production wells in Xinjiang Oilfield in an environment with high CO₂ and high Cl⁻ content.

Method  The most suitable corrosion inhibitor was selected through electrochemical testing in an environment of atmospheric pressure, 60 ℃, and harsh salinity, and the corrosion inhibition rates under wellbore temperature conditions in different blocks were tested. Molecular dynamics simulation revealed the influence mechanism of temperature on the adsorption of the selected corrosion inhibitor on the surface of steel. The protective effect of the corrosion inhibitor under simulated working conditions was obtained through high-temperature and high-pressure autoclave experiments, and the field application effect was clarified through long-period underground hanging rings.

Result Laboratory experimental results showed that quinoline quaternary ammonium salt had a better corrosion inhibition in high CO₂-containing environments, with a corrosion inhibition rate of more than 90%. When the temperature increased from 50 ℃ to 80 ℃, its corrosion inhibition rate decreased from 94.86% to 90.86%. The increase of temperature reduced the molecular adsorption energy of the corrosion inhibitor and weakened the protective performance. Field application results showed that after the corrosion inhibitor injection concentration in the main block of the CCUS demonstration area of Xinjiang Oilfield was reduced to 200 mg/L, the wellbore corrosion rate could be controlled within 0.0592 mm/a.

Conclusion Quinoline quaternary ammonium salt corrosion inhibitor has excellent corrosion inhibition performance in a high CO₂ and high Cl⁻ content environment and can be used for corrosion control in wellbores under CO₂ flooding production conditions.