The drill pipe joint is an integral part of the drill pipe, which is divided into a male joint and a female joint, and is connected to both ends of the drill pipe body. In order to enhance the connection strength of the joint, it is necessary to increase the wall thickness of the pipe body at the joint part. According to the thickening method, it can be divided into three forms: internal thickening, external thickening, and internal and external thickening. There are threads (coarse buckles) on the joints, which are used to connect each single drill pipe. The drill pipe joint thread is a tapered pipe thread with a sealing shoulder. The shoulder surface is tightened for sealing, and the thread is only for connection. The thickening method is different, and the screw type of the corresponding joint is also different. There are four types of threaded drill pipe joints: inner flat (IF), through-hole (FH), regular (REG); digital (NC). Buckle connection condition The snap connection must meet three conditions: ①Equal size; ②The thread type is the same; ③ Match the male and female buckles.

Drill pipe is divided into three categories: kelly, drill pipe and weighted drill pipe. The connection sequence is kelly (1 piece) + drill pipe (n piece, determined by well depth) + weighted drill pipe (n piece, determined by drilling tool assembly design). Kelly The kelly is located at the top end of the drill string, and there are two types: square and hexagonal. effect ①When drilling, the kelly is matched with the compensation center and the rotary table compensation center, and the ground rotation torque is transmitted to the drill pipe, so as to drive the drill string and the drill bit to rotate; ② Bear the full weight of the drill string; ③ Channels for drilling fluid circulation.

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.