Classification of drill pipe joints
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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.
Today we mainly learn about the drill pipe joint. The drill pipe joint is an integral part of the drill pipe. It is divided into a male joint and a female joint, which are connected to 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 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.
Button type of drill pipe joint
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, the drilling fluid flow resistance is large, and the relative flow resistance is the largest among the three buckle types, but the outer diameter is small 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.
