Introduction to drilling pipe

1. Casing

During the drilling process or after the completion of drilling, one or several steel pipes are lowered into an oil and gas well according to the design requirements to prevent the well wall from collapsing, separate the fluids in each layer, and form oil and gas production channels. This kind of steel pipe is called casing.

2. Oil pipe
Oil pipe is a special pipe material for oil wells. According to the thickening situation, the oil pipe is divided into two-end thickened oil pipe and flat oil pipe. The two-end thickened oil pipe is used for deep well completion work, and the length of the oil pipe is generally 6 to 10 meters.

3. Sucker rod
1) Technical specifications of the sucker rod

The main body of the sucker rod is a solid rod with a circular cross-section, with thickened forging heads at both ends, and the forging heads have connecting threads and square sections for wrenches. The nominal diameters of the sucker rod are 16 mm (5/8 inch), 19 mm (3/4 inch), 22 mm (7/8 inch) and 25 mm (1 inch). The length of the sucker rod, in addition to the most common 8-meter sucker rod, there are five lengths of 1.0m, 1.5m, 2.5m, 3.0m, and 4.0m specially processed for combination.

2) Material of the sucker rod

There are two types of domestic sucker rods, one is carbon steel sucker rod and the other is alloy steel sucker rod. Carbon steel sucker rods are generally made of No. 40 high-quality carbon steel, and alloy steel sucker rods are generally made of No. 20 chrome-molybdenum steel or No. 15 nickel-molybdenum steel.

3) Grades of sucker rods

Divided into three grades: C, D, and K

(1) Grade C has low tensile strength (620-794MPa), suitable for shallow wells and medium-deep wells with light and medium loads and slight salt water corrosion;

(2) Grade D has high tensile strength (794-965MPa), suitable for medium and heavy loads and medium and deep wells with slight salt water corrosion;

(3) Grade K has the lowest tensile strength (588-794MPa), suitable for wells with light and medium loads and corrosive media such as hydrogen sulfide and carbon dioxide.

4. Drill pipe

Drill pipe is the basic unit of the drill string. It mainly transmits the torque of the rotary table and the load and establishes the working fluid circulation channel. It is the basic supporting special pipe to complete the well repair process. The joints equipped with the drill pipe itself are collectively called drill pipe joints. They are used in pairs, that is, a drill pipe is equipped with male and female joints at both ends. Its function is to connect and protect the drill pipe for easy buckling.

The oil drill pipe joint consists of the clamp fastening part, welding part, joint thread and sealing shoulder, etc. It is divided into internal thread joint and external thread joint, which are used in pairs.
The drill pipe is the basic component of the drill string. It is made of seamless steel pipe (the wall thickness is generally 9~11mm). Its main function is to transmit torque and transport drilling fluid, and the wellbore is deepened by gradually lengthening the drill pipe. Therefore, the drill pipe occupies a very important position in oil drilling.