Difference between oil tubing and casing pipe

Oil tubing and casing pipe are steel pipes used in the oil drilling process. They are both steel pipe products. Due to their different applications in drilling work, there are also great differences in the selection of production processes and technical standards.

Difference between oil tubing and casing pipe:

1. Different uses

Oil tubing is mainly used to transport oil and gas from underground to the ground. The pressure resistance and corrosion resistance of oil pipes are very strong, which can ensure the safety and smooth progress of oil drilling work. They are shallow in the well.

Casing pipe is used to support the well wall or wellbore, keep the wellbore stable, and prevent the wellbore from collapsing. Because the casing is at a deeper position in the well, the requirements for it are higher than those for tubing.

2. Different sizes
Size: The diameter of the casing pipe is usually larger than that of the oil tubing. Casing pipe is available in a variety of sizes, usually with a diameter of 4 1/2 inches to 20 inches, while the diameter of the tubing is usually between 1 1/2 inches and 4 1/2 inches.

Length: Casing pipe is usually longer than tubing, and can be up to 40 feet or more in length. Tubing is usually 25 to 30 feet long.

Thickness: Casing pipe is usually thicker than tubing to withstand the weight of the overlying rock and the pressure of the fluids contained therein. The thickness of casing pipe can vary depending on the depth and pressure of the well, but it is usually between 0.25 and 1 inch. On the other hand, tubing is thinner, with a thickness between 0.10 and 0.25 inches.

3. Different materials
Casing is usually made of steel, and the grade and type of steel depends on the conditions in the well. Common materials for oil casing pipe are mainly carbon steel, stainless steel and alloy steel.
Tubing can be made of steel, plastic or other materials, depending on the specific application.

4. Different structures
Tubing and casing pipe are also different in structure. Tubing is usually made of light steel pipe with a smooth surface and relatively simple structure. Casing, on the other hand, needs to withstand greater weight and pressure, so it is usually made of thicker steel and combined with some support structure to increase its stability.

5. Different performance
The application environment of oil tubing and casing is somewhat different, so their performance is also different. Oil tubing needs to withstand the impact and corrosion of the conveying fluid, so it needs to be subjected to more complex surface treatment to improve its corrosion resistance and wear resistance. Casing pipe needs to withstand higher pressure, so it is usually made of more corrosion-resistant materials and strengthened on the surface.

6. Different connection methods
The connection on the casing is usually threaded, allowing the sections to be screwed together to form a continuous pipe string. Tubing connections can be threaded or welded, depending on the application.

Differences in production process between oil tubing and casing pipe:

Although oil tubing and casing pipe look very similar in appearance, there are great differences in production process.

1. Different material selection
The thickness of oil tubing is relatively thin, mainly because it has strong pressure resistance and corrosion resistance, so it does not require a too thick pipe wall. The thickness required for casing is thicker than that of tubing because it has to withstand greater pressure and gravity.

2. Different process flow
The casing pipe production process is complex, involving multiple bends, high-precision thread processing, seamless steel pipe hot rolling and other technologies. In contrast, the oil pipe production process is simple, mainly including steel pipe processing, steel pipe hot rolling, casing finishing and other processes.

3. Different testing standards

After the casing pipe is produced, it is necessary to test and measure multiple indicators such as thread and pipe wall density, and strict tests such as pressure testing are also required. For oil pipes, only some conventional indicators need to be roughly inspected.

Read more: Casing pipe vs Drill pipe or API 5CT Steel Casing and Tubing Chart