Reasons and Suggestions for the Failure of a Certain Oil Pipe Fracture

Regarding the fracture failure of P110S tubing in a high-temperature, high-pressure deep well during sudden well shutdown, the causes of tubing fracture and the impact of well shutdown operations were systematically studied through macro-fractography observation, physicochemical performance testing, corrosion product analysis, micro-morphology characterization, and mechanical simulation. The results indicate that there was significant localized corrosion at the fracture location, forming a corrosion risk area; during the well shutdown process, the temperature dropped sharply by approximately 40 ℃, and the absence of an expansion joint in the tubing led to a significant increase in tensile stress at that location. Under the combined effects of corrosion and tensile stress, localized stress corrosion cracking occurred in the tubing section, ultimately leading to fracture as the stress exceeded the material's tensile strength. It is recommended to install expansion joints in such tubing to compensate for thermal and pressure-induced expansion and contraction, and to adopt a gradual and slow well shutdown process, controlling the temperature drop at the wellhead to no more than 20 ℃.