Causes of corrosion perforation of N80 steel tubing in an oilfield water injection well

Corrosion perforation occurred in N80 steel tubing of an oilfield water injection well. The causes of corrosion perforation of tubing were analyzed by means of macroscopic observation, chemical composition analysis, mechanical property test, metallographic examination, scanning electron microscope and energy spectrum analysis, and X-ray diffraction analysis. The results show that there were a lot of CO₂ and H₂S in the field water, which caused corrosion of the oil tubing, and the corrosion products were attached to the pipe wall. At the same time, there were a lot of Cl^－ in the injected water. Under the action of Cl^－, pitting corrosion gradually occurred on the oil tubing. A variety of corrosion effects worked together, resulting in serious local corrosion of the tubing, and the local corrosion defects gradually expanded, eventually formed a corrosion perforation.