Fracture Causes of External Upset P110 Tubing

A external upset P110 tubing with a size of ϕ73.02 mm×5.51 mm used in a tight sandstone gas well was fractured. The fracture causes of the tubing were analyzed by means of macro/micro-morphology observation, chemical composition analysis, microstructure obsevation and mechanical property testing. The results show that the fractured tubing was located on the upper part of the tubing string, and subjected to a high axial tensile stress, and its material had a high sensitivity to sulfide stress corrosion cracking, and the H₂S in produced gas of the gas well provided sulfide corrosion environment for the tubing, resulting in the sulfide stress corrosion cracking of the external upset tubing. The hardness of the tubing was high, and there was a large sulfide inclusion in the structure, which promoted the fracture of the tubing.