Classification Of Drill Pipe Joints

Classification of drill pipe joints
The drill pipe joint is an integral part of the drill pipe, which is divided into male joint and female joint, and is connected at both ends of the drill pipe body. In order to enhance the connection strength of the joint, the wall thickness of the pipe body needs to be increased at the joint. According to the way of thickening, it can be divided into three forms: internal thickening, external thickening, and internal and external thickening. There is thread (coarse thread) on the joint to connect each single drill pipe and drill pipe joint. The thread is a taper pipe thread with a sealing shoulder. The tightening of the shoulder surface plays a sealing role, while the thread only plays a connecting role. Different thickening methods lead to different thread types of corresponding joints.
Drill pipe joints are divided into four types according to thread thread type: internal flat (IF), through hole (FH) and regular (REG); Number (NC).
Buckle connection conditions
Three conditions must be met for buckle connection:
① Equal size;
② The thread type is the same;
③ The male and female buttons match.
Thread type of drill pipe joint
Internal flat type: mainly used for external thickening of drill pipe. It is characterized by the same inner diameter of drill pipe and small flow resistance of drilling fluid; But the outer diameter is large and easy to wear. Through hole type: mainly used for internal and external thickening of drill pipe. Its characteristics are that the drill pipe has two inner diameters, and the flow resistance of drilling fluid is greater than that of the inner flat type, but its outer diameter is smaller than that of the normal type. Normal type: mainly used for thickened drill pipe, drill bit and fishing tool. Its characteristics are that the inner diameter of the thickened joint is smaller than the inner diameter of the pipe body, and the drilling fluid flow resistance is large. Among the three types of buckles, the relative flow resistance is the largest, but the outer diameter is the smallest, and the strength is large. The above three types of joints adopt V-type thread, but the thread type, thread distance, taper and size are very different.
The digital type (NC) series connector is the American national standard coarse thread series. It has been adopted as an international standard by API. NC thread is also V-type thread. Some NC type joints have the same pitch diameter, taper, pitch and thread length as the old API standard joints and can be interchanged.
Most oil drill pipe joints are externally thickened or internally thickened. The outer diameter of the drill pipe joint is larger than the outer diameter of the pipe body. During the drilling process, the drill pipe joint constantly contacts and rubs with the well wall or casing, resulting in wear. In order to avoid drilling accidents such as broken drill pipe and tripping caused by joint wear, the drill pipe joint wear belt must be set on the drill pipe mother joint