Classification and function of drill pipe

The drill pipe is a steel pipe with a thread 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 raise, lower or rotate the bottom hole device together with the drill bit. The drill pipe must be able to withstand huge internal and external pressure, distortion, bending and vibration. In the process of oil and gas extraction and refining, the drill pipe can be used many times.

Drill rods are divided into three categories: kelly rods, drill rods, and weighted drill rods. The connection sequence is kelly (1) + drill pipe (n, determined by the depth of the well) + weighted drill pipe (n, determined by the design of the drill tool assembly).

Kelly

The kelly is located at the top end of the drill string, and there are two types: square and hexagon

①When drilling, the kelly rod is matched with the core and the turntable to transfer the ground rotation torque to the drill rod to drive the drill string and the drill bit to rotate;

② Bearing the full weight of the drill string;

③ Channel for circulation of drilling fluid.

structure

The kelly rod is composed of upper and lower joints and a pipe body. The pipe body has two structures: square or hexagonal structure (most of the oil drilling is square structure); the upper joint is a left-handed female thread (reverse buckle), which is connected to the faucet, and the left-handed female thread prevents reverse buckling during the rotation process; the lower joint It is a right-handed male thread, which is connected with the drill pipe. When working, the upper end of the kelly rod is always above the surface of the turntable, and the lower part is below the surface of the turntable.

Drill pipe

The drill pipe is the basic part of the drill string. Its main function is to transmit torque and transport drilling fluid, and to deepen the borehole continuously by the gradual lengthening of the drill pipe. Therefore, drill pipe occupies a very important position in oil drilling.

structure

The wall thickness of seamless drill pipe is generally 9-11mm; the pipe body and the joint are butt welded together by friction welding.

Heavy drill pipe

Heavy drill pipe is similar to oil drill pipe, but also a hollow steel column with a length of about 10 meters. However, the weight of a single rod is heavier than that of oil drill pipes, and the wall thickness is 2 to 3 times that of drill rods. The heavier drill rod is connected between the drill rod and the drill collar to prevent fatigue damage due to the change of the drill string cross section. It can also replace part of the role of the drill collar, but its suspension is simple, and the operation of starting and running is convenient, which can save the time of starting and running.