Hyperduplex Stainless Steel, UNS S33207, for Raw Seawater Injection

Raw seawater injection is a more and more used technology in oil production. The injection of water allows that more oil can be retrieved from a well. A large advantage to use raw seawater compared to treated seawater is that no surveillance is needed and hence the manning can be reduced. However, raw seawater requires the use of more corrosion resistant alloys than treated seawater that has high strength. UNS S33207 is a newly developed hyperduplex stainless steel for umbilicals. It has a minimum PRE of 50. Recently large diameter tubing has been developed with minimum yield strength of 100 ksi in solution annealed condition, which result in a high strength material with low level of anisotropy. In addition to reporting the mechanical properties of the large diameter tubing, the aim is to show that UNS S33207 is a good candidate tubing material for raw seawater injection where threaded connections are used. The crevice corrosion resistance is evaluated by laboratory testing and compared to earlier test programs of Ni-based alloys. Crevice corrosion testing of UNS S33207 in natural seawater with severe crevices has been performed and indicates very good crevice corrosion resistance. Further stress corrosion cracking in chloride environments will be discussed.

Keywords: Hyperduplex, Raw seawater injection, Crevice corrosion, Stress Corrosion cracking, Tubing