Difference between casing pipe and drill pipe

The difference between casing and drill pipe:

Casing pipe: It is an important component of well cementing. It plays the role of fixing the well wall and oil pipe in the well hole to prevent oil and gas from leaking in the well.
Drill pipe: refers to a long rod used when drilling holes in rock formations. The drill bit or drill bit assembly can be sent down the hole for use.

1. Different uses

Casing and drill pipe play different roles in the drilling process. Casing is a pipe that is put into the wellbore to ensure the stability of the well wall and prevent oil and gas leakage. It is also a pipe that connects the surface equipment and the wellhead. The drill pipe is used to send the drill bit to the bottom of the well and perform detection and sampling work.

2. Different materials

The materials of casing and drill pipe also vary. Casing pipes are typically made from carbon steel or stainless steel to withstand the challenges of high pressure and temperature found in underground environments. Stainless steel pipe offers superior strength, corrosion resistance and maximum durability. Carbon steel pipe also resists the harsh environment of the oil field well, but is not as corrosion-resistant as stainless steel casing. However, it is cheaper and more cost-effective, and the use of corrosion inhibitors prevents rust and subsequent degradation.

Drill pipe is made of high-strength alloy steel or aluminum alloy, which can withstand extreme drilling conditions while maintaining structural integrity, such as high stress and pressure, high temperature, tension and corrosion, ensuring it can withstand high pressure at the bottom of the hole and strong geological reactions. Aluminum is another material used to make drill pipe and is best suited for situations where a lighter weight drill pipe is more convenient, such as during horizontal or directional drilling.

3. Different structures

There are also differences in the construction of casing and drill pipe. Casings are generally immersed tubes with different wall thicknesses and different cross-sectional dimensions and collapse pressures. The upper part of the casing has a smaller diameter and the lower part has a larger diameter in order to reduce the diameter of the wellbore and withstand geological pressure. Drill pipe, on the other hand, is a series of long tubes and rods, sometimes using different types of steel and connectors. A weight is often added to the lower part to facilitate the downward push by gravity. The length of drill pipe is determined by the well depth and drilling target, while the casing length is basically equal to the well depth.

4. Different standards
There are different standards for casing and drill pipe. The American Petroleum Institute (API) sets manufacturing standards for oil and gas well drill pipe and casing to ensure the safety and reliability of drilling operations.

The bushing adheres to API standard 5CT specifications. Steel casing pipe must be manufactured from materials with sufficient strength to withstand challenging drilling conditions, such as higher depths. The API 5CT standard covers requirements for various casing materials or steel grades, including but not limited to J55, K55, N80 and P110, etc.

API 5D specifications, on the other hand, are a combination of API standards’ requirements for oil drill pipe. API 5D covers various wall thickness steel grades used in drill pipe construction, including E-75, X-95, G-105 and S-135. 
These also define the minimum yield strength of the drill pipe. Grade E drill pipe belongs to Group 1 and has the lowest yield strength, while material grades X, G and S belong to Group 3 and are high-strength grades used for deep drilling.

5. The connection between the two

Although casing and drill pipe are different in structure and purpose, they are related to each other. That is, during the drilling process, the casing is fed into the wellbore layer by layer through the drill pipe, and penetrates the drill pipe. It serves as a bridge between surface equipment and bottom-hole work, and the two are closely related to each other.

Summarize:

Casing and drill pipe are essential tools in oil drilling. Although their uses, materials, structures and standards are different, the two are related to each other. Only the correct use of casing and drill pipe can ensure safe, efficient and successful drilling.

About us:

Hunan Standard Steel Co.,Ltd (HSCO) is a leading manufacturer and supplier of drill pipe and oil casing. We offer high-quality drill pipes, casing pipes (seamless casing and erw casing), couplings and other products that can withstand the harshest conditions during drilling and ensure maximum drilling efficiency.

Contact us today for a custom estimate on our drill pipe and casing, which are manufactured to the highest quality standards for optimal performance in the oil field: info@hu-steel.com