Seamless Casing Grade and Connection Type Chart

Seamless casing and connection is considered the most commonly utilized oil-field casing today. Seamless casing is produced in a pipe mill using a billet, a solid cylindrical piece of steel.

The manufacturing process takes place through the exposure of the billet to high temperature; billet penetration using a mandrel; passage of the billet into the rollers and internal mandrels to size it up; treatment of the tube with heat; and straightening and final sizing.

Seamless Casing and Connection Features

The dimensional and wall thickness specifications of oil well seamless casing ranges from 1/8 inch to 26 inches OD. It is particularly suited for high-pressure operations, including oil and gas exploration and drilling, hydrocarbon industries and refineries, and oil and gas transportation.

The threading of the connections of the seamless casing may be done either by the manufacturer or by other companies. Ensuring the uniformity of the seamless casing wall thickness is a challenge to manufacturers. The production process may cause slight eccentricity to the cross section of the seamless casing wall.

Seamless Casing and Connection over Welded Type

Seamless casing and connection presents advantages over the welded type. The primary advantage of the seamless casing for oil well is the absence of a weld seam, which is considered a weak spot that can pose risks of failure and corrosion. In addition, better roundness is seen with seamless casing and connection. Lastly, the possibility of having a weak seam is omitted.

The only weak points associated with seamless casing and connection for oil wells are the disparities in wall thickness, challenges in the production process, and the higher costs.
 

Seamless Casing Grade and Connection Type Chart

Seamless Casing Grade and Connection Type Chart Abbreviations:

• in. – Inches
• mm – millimeter
• lb/ft – pounds per feet
• kg/m – kilogram per meter
• P – Plain Ends
• S – Short round thread
• L – Long round thread
• B – Buttress thread

Casing Specification:

In utilizing seamless casing and connection, the purchaser and designer should follow the standards set by the American Petroleum Institute (API). The organization provides a variety of manufacturing standards for tubing and casing, which are also adopted by the International Standards Organization (ISO).

Casing specifications are usually presented in outer diameter (in or mm), nominal weight (lb/ft or kg/m), wall thickness (in or mm), and grade and connection type.

Outer Diameter

Outer diameter is usually fixed for a particular size.

Nominal Weight

The nominal weight presented in lb/ft or kg/m portrays the average linear weight of the seamless casing and connection, which limits the casing wall thickness that in turn defines the inner diameter.

Grade

The yield strength and material composition of the seamless casing are indicated by the grade of the casing.

Connection Type

The connection type shows the type of thread used to affix the oil well seamless casing joints. Premium connections can be defined as:

• P – plain end
• S – short round thread
• B – buttress
• L – long round thread

Go here if you are looking for the API Casing Specification Chart.