Corrosion Cracking Cause of Coiled Tubing in Gas Lift Operation

A coiled tubing in an offshore gas well cracked and suffered serious corrosion after nitrogen gas-lift operation for 61.5 h. The failure cause of the tubing was studied by macro and micro analysis, physical and chemical properties testing, X-ray energy spectrum analysis and stimulated corrosion test. The results showed that the combined effect of O2 carried by N2 and CO2 in the wet gas well corroded the coiled tubing. The O2 corrosion was the main reason of the corrosion of coiled tubing in short time. According to the results and the on-site conditions, measures to remove O2 was taken and the corrosion problem was resolved.