Steel Grade Difference between Drill Pipe and Oil Casing Pipe

Casing Pipe:

Petroleum casing pipes are steel pipes used to support the walls of oil and gas wells to ensure the normal operation of the entire oil well after drilling and completion. Each well uses several layers of casing according to different drilling depths and geological conditions. Cement is used to cement the casing after the casing is down. It is different from tubing and drill pipe and cannot be reused. It is a disposable material. Therefore, casing consumption accounts for more than 70% of all oil well pipes.
According to the application, petroleum casing can be divided into conduit casing, surface casing, technical casing and reservoir casing.

Petroleum casing pipes can be divided into different steel grades according to the strength of the steel itself, namely J55, K55, N80, L80, C90, T95, P110, Q125, V150, etc. Processing form of casing end: short round thread, long round thread, partial trapezoidal thread, special buckle type, etc. Different well conditions and depths have different steel grades. In a corrosive environment, the casing itself is also required to have corrosion resistance. In places with complex geological conditions, the casing is also required to have anti-collapse performance. It is mainly used to support the well wall during drilling and after completion to ensure the progress of the drilling process and the normal operation of the entire well after completion.

Drill Pipe:
Petroleum 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, twisting, 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 types: Kelly rods, drill rods and heavy drill rods.

The steel grade of oil drill pipe refers to the grade of drill pipe steel, which is determined by the yield strength of the drill pipe steel. API (American Petroleum Institute) divides drill pipe steel grades into five grades: D, E, 95(X), 105(G), 135(S). The higher the drill pipe steel grade, 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, it is recommended to increase the strength of the drill string by increasing the steel grade, instead of increasing the thickness of the wall.

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