Application Limits for 110ksi Strength Grade Super 13Cr Steel in CO2 Environments Containing Small Amounts of H2S

110ksi strength grade-super 13Cr steels have been developed and widely used as an OCTG tubing material for CO₂ environments containing small amounts of H₂S. However, the application limits are not clear due to the complex interaction of the environmental-related factors, such as chloride concentration, pH and H₂S partial pressure, on the sulfide stress cracking and high temperature stress corrosion cracking resistance. A 110ksi strength grade-super 13Cr steel, UNS S41426, was evaluated for it’s SSC resistance in accordance with Method A of NACE TM0177-96. The SSC-resistant domains for 110ksi grade super 13Cr steel are proposed as a function of Cl^- concentration, pH and H₂S partial pressure. The influence of Cl^- concentration was larger for the lower pH or higher H₂S partial pressure environments. The SCC resistance was evaluated by the four-point bend beam test technique. The SCC-resistant domain in 0.001MPa H₂S environment at 175^oC was influenced by Cl^- concentration and pH. Super 13Cr steel suffered from SCC at low pH and high Cl^- ion concentration even within the SSC-resistant domain.  From these test results, it is suggested that the cracking resistance should be evaluated at the maximum service temperature, as well as at 25^oC, when evaluating the application limits for super 13Cr steels.