Fracture reason of tubing joint in a production well

The tubing joint of a production well in an oilfield was fractured. The fracture reason was analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination, mechanical property test, scanning electron microscope and energy spectrum analysis. The results show that the upsetting process and structural characteristics led to the uneven mechanical properties of the joint, and the inner wall of the joint produced tiny corrosion pits and initiated cracks under the action of corrosive medium. Under the combined action of environment and load, the crack propagated and eventually led to the insufficient residual strength of the material, then the joint cracked.