Corrosion Studies on Casing Steel in CO2 Storage Environments

Abstract

The corrosion behavior of casing steel N80 in brine plus CO 2 was studied in autoclave to simulate the CO 2 storage environment. The brine solution used in the study contained 130 g/l NaCl, 22.2 g/l CaCl 2 and 4 g/l MgCl 2 . The CO 2 was charged in the autoclave at different pressures (60, 80 and 100 bar) and at 45 °C. The corrosion rate was measured using electrochemical and mass loss measurements. The surface of the samples after exposure to CO 2 and brine was analyzed using SEM, EDS and XRD. The polarization results show that the corrosion rate of N80 steel in the brine plus CO 2 is 6 mm/y in 1 hour and 0.3 mm/y after one week at 80 bar and 45C°. The corrosion of the steel at other pressures shows a similar behaviour. The mass loss measurements show the average corrosion rate 0.06 mm/y after immersion for 32 days. The decrease of the corrosion rate for N80 steel in this environment is attributed to the formation of dolomite layer on the sample surface.