Unraveling the effect of H2S on the corrosion behavior of high strength sulfur-resistant steel in CO2/H2S/Cl− environments at ultra high temperature and high pressure

The effect of H2S on the corrosion products for the corrosion of high strength sulfur-resistant steel was investigated in oilfield produced water under supercritical CO2 conditions by SEM-EDS, LSCM, FIB-SEM, XRD, XPS and theoretical simulation calculations. The results show that with the increase of PH2S, the corrosion degree changes from mild corrosion to moderate corrosion in SC-CO2 phase, while the corrosion rate decreases in aqueous phase. And also the localized corrosion was more severe in SC-CO2 phase. The structure of the corrosion product on high strength sulfur-resistant steel surface evolved from monolayer to bilayer with the increase of PH2S in the SC-CO2 phase. The bilayer corrosion product structure is composed of the inner layer of iron sulfide, FeCO3 and a small amount of Cr(OH)3, and outer layer of FeCO3. However, the corrosion products are bilayered structure in the aqueous phase, and the density of the scales increases with the increase of H2S partial pressure, which reduces the corrosion of high strength sulfur-resistant steel. The results provide guidance for the material selection of oil and gas fields.