Causes Analysis on Pulling out of a Premium Connection Tubing in One Well

A thorough investigation was done on the pulling out accident of a premium connection tubing in one well. The macro analysis, geometry dimension measurement, metallographic analysis, mechanical performance test and chemical composition analysis were carried out to the failure tubing samples. The stress state of the tubing was analyzed, and time order of the tubing connection pulling out and the coupling cracking was deduced. The results show that the tubing connection was pulled out due to the brittle cracking of the coupling, and the coupling cracking was mainly related to the high yield strength and high hardness of its material as well as the temperature load of the tubing during repairing well.