Applicability of 3 Stainless Steels in H₂S/CO₂ and High Salinity Brine Environment

The corrosion resistance of ordinary martensitic stainless steel 13Cr, super martensitic stainless steel HP2-13Cr and duplex stainless steel 22Cr in high salinity oil-gas-water multiphase flow containing CO₂ and H₂S was studied through high temperature and high pressure simulation test, field coupon test, electrochemical test, and corrosion morphology observation. The effect of crude oil on the corrosion resistance of stainless steel, especially on the pitting mechanism, was explored. The results showed that the uniform corrosion rates of 13Cr, HP2-13Cr and 22Cr were 0.107 7 mm/a, 0.099 4 mm/a and 0.003 4 mm/a, respectively, after a 90 day field coupon test. In H₂S saturated solution, HP2-13Cr was easier to passivate than 22Cr; the reactivation rate of HP2-13Cr was higher than that of 22Cr in H₂S-free environment, and the reactivation rate of HP2-13Cr was lower than that of 22Cr after being aerated with saturated H₂S. In the environment containing crude oil, H₂S, CO₂, Cl^- and water, 13Cr suffered localized corrosion, 22Cr suffered pitting, and HP2-13Cr suffered uniform corrosion.