The failure of thread tooth fracture accounts for about 70% of drill pipe failures. According to the analysis of the cause of thread tooth fracture failure, the following preventive measures can effectively reduce the incidence of this type of failure:
(1) When processing threads, avoid producing incomplete threads at the end of the thread (the place where the tool is retracted) to prevent stress collection in the extension drilling tools from causing fatigue damage to the thread teeth.
(2) Take appropriate sealing measures at the bottom of the coupling and the inner end of the external thread, try to avoid the fluid in the pipeline from entering the threaded joint, reduce corrosive wear, and prevent the thread from rusting and causing its insufficient strength.
(3) Non-destructive testing such as radiographic inspection or magnetic particle inspection of extension drilling tools is carried out on the processed threads, and the surface and internal defects of the pipe thread parts are found in time to avoid defective threaded threads going down the well.
(4) Use a suitable torque to tighten the thread to avoid breaking the thread due to the excessive pre-tightening force that exceeds the strength limit of the thread material.