Causes Analysis on Fracture of the Tubing Joint

During the process of pulling the oil pipes in one well, it was found that the tubing joint (88.90 mm×6.45 mm) in lower end of tubing hanger had fractured. The fracture reasons of the tubing joint were analyzed by means of macrographic examination, chemical composition analysis, mechanical property test, microstructure analysis, macro and micro fracture analysis. The results show that the fracture type of the tubing joint was overload fracture. The fracture reason was that the designed tensile margin of external thread of the tubing joint was relatively low. Meanwhile, the eccentricity existed in the thread processing of the tubing joint, leading to a certain decline of the bearing capacity of the tubing joint.