Failure Analysis of Tubing During Ignition Process in In-situ Combustion Gas Injection Well

After nearly ten years, the pilot test of in-situ combustion in the HQ1 area of the near-abandoned oil reservoir after steam injection development in Xinjiang Oilfield has achieved phased achievements. Based on this experience, the area started industrialization trials in 2018. During the ignition process of a gas injection well, the ignition string suddenly broke and fell into the bottom of the well, and the ignition operation was forced to stop, which had a serious impact on the production operation. Through chemical composition, mechanical test, microstructure observation, metallographic analysis, corrosion products were tested, so as to analyze the failure cause of the tubing fracture. The results show that the fracture of the N80 tubing is mainly due to the abnormal microstructure caused by corrosion in high temperature environment and the thinning of the tube wall, which leads to the decrease of bearing capacity and impact resistance and fracture. The study results will provide a brief reference for the safety and efficiency of subsequent ignition operations.