The drill pipe is a steel pipe with a thread at the end, which is used to connect the surface equipment of the drilling rig and the drilling and grinding equipment or bottom hole device at the bottom of the well. The purpose of the drill pipe is to transport the drilling mud to the drill bit and together with the drill bit raise, lower or rotate the bottom hole device. Drill pipe must be able to withstand enormous internal and external pressure, twisting, bending and vibration. In the process of oil and gas extraction and refining, drill pipe can be used many times. The bare and raw steel pipes are made into drill pipes after several processing steps. First, through the processing of the steel pipe thickening process, the outer surface of the light pipe is bent inward, and the pipe wall of the steel pipe is thickened. The next step is threading and plating with copper for strength. A non-destructive quality control inspection is then carried out, followed by welding of the steel pipe body joint. Afterwards, the tube undergoes a welding heat treatment and a welding final treatment to relieve welding residual stress. Several other tests are performed on the finished steel pipe before the finished drill pipe is painted and packaged, including hardness testing, pressure testing and non-destructive testing.
The usual components of the drill string are: drill bit, drill collar, drill pipe, stabilizer, special joint and kelly. The basic functions of the drill string are: (1) Trigger the drill bit; (2) Apply weight on bit; (3) Transmission of power; (4) Transport drilling fluid; (5) Carry out special operations: squeeze cement, deal with underground accidents, etc.