Development of Sour Resistant Modified 13CR OCTG Available to Purchase

Sour resistant 13% Cr martensltic OCTG (Oil Country Tubular Goods) with so far unexpected high CO₂ corrosion resistance was developed. CO₂ corrosion resistance was remarkably increased by complex additions of Cu and Ni, of which contribution to CO₂ corrosion resistance corresponds to that by a further addition of 6% Cr at 180°C. SSC resistance was Inproved by an addition of Mo. Based on such knowledge of roles of chemical elenents on corrosion properties and phase stability, 0.02%C-12.5%Cr-4.5%Ni-1.5%Mo-1.5*Cu steel was developed. This steel has good hot-workability and was produced into seamless OCTG. Corrosion rates in a high pressure CO₂ environment were less than 0.1 mra/y at temperatures up to 200°0 (392 F) compared with 100°C of conventional API L80-13CR. No SSC occurred in sour environments with partial pressure of 0.001MPa or less even at low pH of 3.5. At elevated temperatures no cracking and no pitting was observed in H₂S containing CO₂-brine environments. The properties of the developed steel are much better in CO₂ corrosion and SSC resistance compared with those of conventional 13Cr steel and are close to those of duplex stainless steel.