Corrosion resistance of 316L stainless steel in simulated CO₂-bearing crude oil

In order to further master the adaptability of 316L stainless steel, the corrosion law of 316L stainless steel coupon was studied in high-temperature and high-pressure reaction kettle by taking the medium produced at the test point after CO₂ flooding as the main solution. The tests were carried out by taking Cl^- mass concentration, Ca²⁺ mass concentration, CO₂ partial pressure, temperature, flow speed and oil-water ratio as the influencing factors, and then the morphology and electrochemical characteristics of the coupon with the highest corrosion rate in the test range were observed and analyzed using the electron microscope and electrochemical workstation. The test results show that under the Cl^- mass concentration of 3 000-50 000 mg/L, the Ca²⁺ mass concentration of 100-6 000 mg/L, the CO₂ partial pressure of 0.15-0.75 MPa, the temperature of 15-55 ℃, the flow speed of 0-0.5 m/s and the water cut of 20% and 85%, the corrosion rate of 316L stainless steel changes in the order of magnitude of 10^-3-10^-2 mm/a. Electron microscope scanning and energy spectrum analysis reveal that the mass fraction of the corrosion resistant element Mo in the test specimen is slightly higher than the low limit and open pitting pits with slight corrosion appear in the 316L stainless steel in the parts with more Al impurities. It is indicated that 316L stainless steel has good comprehensive corrosion resistance in the test range, but the problem of pitting corrosion shall not be ignored. The mass fractions of Cr, Ni, and Mo in the 316L stainless steel used in the test are slightly higher than the low limits, so it is recommended to pay attention to the mass fraction of favorable trace elements in the process of material selection.