Damage Monitoring of Thread of the Drilling Tool Joint Based on Magnetic Memory Technology

摘要

The frequent drill thread fracture accidents during the drilling process severely affected the exploration and development proceedings of gas resources. To solve this problem, the makeup and breakout fatigue tests on different types of drilling tool joints that used in an oil field in the west of China were carried out. This paper applied the metal magnetic memory technique based on Giant Magneto Resistive to detection the stress concentration degrees of the threaded portion. While the finite element model of the meshing thread has established by the finite element analysis software ABSQUS to verified the experiment. The results demonstrated that the metal magnetic memory technique can well monitor the change process of the stress concentration degrees in the threaded portion and the stress distribution. The test results show that the stress concentration of the first three buckles of NC31 tool joint is the largest. The maximum stress concentration of the NC38 drill joint is the first two buckles near the thread cross section. The change of gradient of the front four buckles of the NC40 drill joint is obvious, and the gradient of the root of the front three buckles of the female joint is obvious. The finite element simulated results show the location of the thread where the stress concentration is high which agree to the experiment. The test provides a data base support for detecting the magnetic memory testing technology to the thread of drill tool, and provides a safe and effective method to reduce the failure of drilling tool thread.