Evaluation of Localized Corrosion Resistance of High Strength 15Cr Steel in Sour Well Environments

As a new corrosion resistant alloy (CRA), high strength 15Cr martensitic stainless steel (0.03C-15Cr-6Ni-2Mo-1Cu) offers an OCTG material for the completion of HTHP deep water wells and large bore gas wells, due to a combination of high specified minimum yield strength (SMYS) of 125 ksi (862 MPa) without cold drawing, good notch toughness, and superior CO₂ corrosion resistance. This paper describes an investigation of the resistance of 15Cr steel to localized corrosion in simulated sour oil and gas well environments at three different temperatures including 75°F (24°C), 200°F (93°C), and 400°F (204°C). The localized corrosion resistance was evaluated using short-term electrochemical potentiostatic polarization tests and long-term (90-day) exposure tests. The long-term exposure test results correlated well with the short-term electrochemical results in terms of localized corrosion susceptibility.