Reasons for Tube Corrosion in a Gas Well Due to Acidizing in Tarim Oilfield

After undergoing two-day fresh acid acidizing and ten-day spent acid flow-back, the oil tube inner wall of a gas wall in Tarim oilfield severely corroded. A comprehensive failure analysis was conducted based on physical testing, chemical analysis, as well as field investigation. The results show that chemical composition and metallurgical structure of the oil tube met the requirement of API Spec 5CT-2005. There were three main reasons contributing to the corrosion failure of the oil tube. Firstly, the fresh acid and spent acid stagnated in tube exceeded the expected operating time; secondly, the high temperature of downhole significantly enhanced the corrosion process; thirdly, inhibitor might not work sufficiently during acidizing process. It is suggested to shorten the operating time of acidizing process, and choose the optimal acidizing inhibitor which could be used at high or extremely high temperatures to reduce the corrosion of oil tube because of acid solution.