Drill pipe is a rod connected with a drill bit and used to transmit power in a drilling tool. 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) tripping the drill bit; (2) applying weight on bit; (3) transmitting power; (4) transporting drilling fluid; (5) performing special operations: squeeze cement, deal with downhole accidents, etc. The purpose of the drill pipe The drill pipe is a steel pipe with ribbing at the tail, 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.

Inner flat type: mainly used for external thickening of drill pipe. Its characteristic is that the drill pipe has the same inner diameter, and the drilling fluid flow resistance is small; but the outer diameter is large, which is easy to wear. Through-hole type: mainly used to thicken drill pipe inside and outside. It is characterized in that the drill pipe has two inner diameters, and the flow resistance of drilling fluid is larger than that of the inner flat type, but its outer diameter is smaller than that of the regular type. Formal type: Mainly used for inner thickening of drill pipes, drill bits and fishing tools. Its characteristics are that the inner diameter of the joint inner diameter is smaller than the inner diameter of the pipe, and the drilling fluid flow resistance is large. The relative flow resistance is the largest among the three buckle types, but the outer diameter is the smallest and the strength is large. The above three types of joints all use V-type threads, but the buckle type, distance, taper and size are very different. Digital (NC) series fittings are American National Standard coarse thread series. It has been adopted as an international standard by API. NC threads are also V-threads, and some NC-type fittings have the same pitch diameter, taper, pitch and thread length as the old API standard fittings and can be used interchangeably. Oil drill pipe joints are mostly in the form of external thickening or internal and external thickening. The outer diameter of the drill pipe joint is larger than the outer diameter of the pipe. During the drilling process, it is constantly in contact and friction with the well wall or casing, resulting in wear and tear. In order to avoid the joint wear and tear, the drill will break Drilling accidents such as rods and tripping must be provided with drill pipe joint wear-resistant belts on the drill pipe female joint.

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.