Seclection of Tubing Materials for a Water Supply Well Containing Low CO₂ in SZ36-1 Oilfield

Corrosion immersion tests were performed for 72 h in a high temperature autoclave under a simulated condition of a water supply well containing low CO₂ in the SZ36-1 oilfield for five kinds of tubing material, N80 steel, 3Cr steel, 13Cr steel, super 13Cr steel and tungsten steel. The corrosion rates obtained from corrosion immersion tests can be used to compare the corrosion resistance of the test steels. Corrosion morphology was observed by optical microscopy to evaluate localized corrosion situations for these steels. The electrochemical properties were analyzed by potentiodynamic polarization curves and electrochemical impedance spectrums. The results show that N80 steel cannot meet the requirements of material selection due to the high corrosion rate of 0.223 mm/a, a large number of pits on its surface, anodic activation controlling its electrochemical corrosion reaction and the smallest electrochemical impedance. Tungsten steel also cannot meet the requirements because of its poor resistance to pitting corrosion. 3Cr steel, 13Cr steel and super 13Cr steel had low corrosion rates, significant anodic passivation characteristics, good pitting resistance, high electrochemical impedance. So these steels can meet the requirements of material selection.