Failure Analysis of Corrosion Perforation of N80S Tubing

On the basis of the survey of service environment, the reasons for N80S tubing perforation failure were elaborated via macroscopic observation, physical and chemical property testing, microstructure observation, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that low pH value and high Cl^- concentration in acidizing fluid and residual acid solution dominantly induced the perforation failure of the tubing. Meanwhile, the effusion in tubing caused by the partial level and inclination of the tubing string deteriorated the pitting. Finnally the tubing corroded and perforated in the position of effusion. Some suggestions were proposed for avoiding this kind of problem again.