Introduction of Drill Pipe

Drill pipe concept:

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.

Main features of drill pipe:

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 painting and packaging the finished drill pipe, including hardness testing, pressure testing and non-destructive testing.

Classification of drill pipe:

Drill pipe is divided into three categories: kelly, drill pipe and weighted drill pipe; the connection sequence is kelly (1 piece) + drill pipe (n pieces, determined by well depth) + weighted drill pipe (n pieces, determined by drilling tool combination) design decision).

1. Kelly

Located at the top of the drill string, there are square and hexagonal.

Effect:

1) When 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.

Structure:

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

2. Drill pipe

Effect:

Drill pipe is the basic component of drill string. Its main function is to transmit torque and transport drilling fluid, and the wellbore is continuously deepened by the gradual lengthening of the drill pipe. Therefore, drill pipe occupies a very important position in oil drilling.

Structure:

Drill pipe structure The drill pipe is made of seamless steel pipe, and the wall thickness is generally 9-11mm; the pipe body and the joint are composed of two parts: the pipe body and the joint of the drill pipe are butt welded together by friction welding.

3. Weighted drill pipe

The weighted drill pipe is similar to the oil drill pipe, and it is also a hollow steel column with a length of about 10 meters. However, the weight of a single piece is heavier than that of the oil drill pipe, and the wall thickness is 2 to 3 times that of the drill pipe. The weighted drill pipe is connected between the drill pipe and the drill collar. It can also replace a part of the drill collar, but its suspension is simple, the tripping and tripping operation is convenient, and the tripping and tripping time can be saved.

Steel grade strength of drill pipe:

The steel grade of the drill pipe refers to the grade of the steel of the drill pipe, which is determined by the yield strength of the steel of the drill pipe. API classifies drill pipe steel into five grades: D, E, 95(X), 105(G), 135(S). The higher the steel grade of the drill pipe, the greater the yield strength of the pipe, and the greater the various strengths of the drill pipe. In the strength design of the drill string, the method of increasing the steel grade is recommended to increase the strength of the drill string, rather than the method of increasing the wall thickness.