The Minaminagaoka field in Japan produces gas containing 6% CO2 and a light condensate. Some wells are completed with 13% Cr-steel tubing. The useful life of these tubulars was less than 6 years with failures occurring mainly due to what appeared to be flow induced localized corrosion. A program was initiated to evaluate commercial inhibitors for the protection of 13% Cr-steel production tubing. Various products from several suppliers were tested under constant contact and filming conditions. The optimum inhibitor was subsequently evaluated in the field. Through an unusual approach to the laboratory test methodology it was established that for water- dispersible as well as non-water-dispersible corrosion inhibitors a distinct hydrocarbon phase is required for good effectiveness. This was at first considered a problem for wells with a hydrocarbon dew point downstream of the choke. It was also concluded that the treatment life observed in the laboratory is many times shorter than the treatment life that could be established by field
measurements. A new proposed model for batch treatment applications attempts to reconcile these observations.
Keywords: API-13Cr Tubing, 13%Cr stainless steel, gas condensate well, CO2 corrosion, flow induced localized corrosion, erosion corrosion, corrosion inhibition, batch treatment, treatment life, inhibitor testing, inhibitor effectiveness.