13%Cr steel tubing corroded at shallow depths in deep, hot Minami-Nagaoka Gascondensate
wells onshore Japan. The produced gas contains 6% CO2 and 2~3ppm H2S, and the
produced water contains 400 ppm acetate. The localized corrosion apparently initiated from mechanical
damages produced by wire line operations. The corrosion damage was more severe in wells with longer
shut in periods. These observations are contradictory to the traditional understanding that the corrosion
performance of 13%Cr steel deteriorates at high temperatures in wet CO2 environments. And
abovementioned observations suggest that the corrosion initiated during well’s shut in period at shallow
depths due to pH lowering by higher CO2 solubility at low temperatures and the existence of acetic acid.
Based on this understanding, corrosion performance of Super 13Cr steel containing Ni and Mo was
evaluated as a potential countermeasure in comparison with 13% Cr and 22Cr steels at a low
temperature in addition to at high temperatures using flow loop and rotating cage. The effect of Clconcentration
and the influence of trace amounts of H2S on the corrosion performance of Super 13Cr
steel was elucidated.
Key words: Corrosion experience, 13%Cr tubing, Super 13Cr steel, sweet environments, acetic acid,
trace amounts of H2S