Casing Standards
The American Petroleum Institute (API) has developed certain standards and specifications for oil-field related casing and tubing. One of the more common standards is weight per unit length. There are three “weights” used:
• Nominal Weight: Based on the theoretical calculated weight per foot for a 20 ft length of threaded and coupled casing joint.
• Plain End Weight: The weight of the joint of casing without the threads and couplings.
• Threaded and Coupled Weight: The weight of a casing joint with threads on both ends and a coupling at one end.
The Plain End Weight, and the Threaded and Coupled Weight are calculated using API formulas. These can be found in API Bulletin 5C3. API standards include three length ranges, which are:
• R-1: Joint length must be within the range of 16 to 25 feet, and 95% must have lengths greater than 18 feet
• R-2: Joint length must be within the range of 25 to 34 feet, and 95% must have lengths greater than 28 feet
• R-3: Joint length must be over 34 feet, and 95% must have lengths greater than 36 feet.
The API grade of casing denotes the steel properties of the casing. The grade has a letter, which designates the grade, and a number, which designates the minimum yield strength in thousands of psi.
The American Petroleum Institute (API) has developed certain standards and specifications for oil-field related casing and tubing. One of the more common standards is weight per unit length. There are three “weights” used:
• Nominal Weight: Based on the theoretical calculated weight per foot for a 20 ft length of threaded and coupled casing joint.
• Plain End Weight: The weight of the joint of casing without the threads and couplings.
• Threaded and Coupled Weight: The weight of a casing joint with threads on both ends and a coupling at one end.
The Plain End Weight, and the Threaded and Coupled Weight are calculated using API formulas. These can be found in API Bulletin 5C3. API standards include three length ranges, which are:
• R-1: Joint length must be within the range of 16 to 25 feet, and 95% must have lengths greater than 18 feet
• R-2: Joint length must be within the range of 25 to 34 feet, and 95% must have lengths greater than 28 feet
• R-3: Joint length must be over 34 feet, and 95% must have lengths greater than 36 feet.
The API grade of casing denotes the steel properties of the casing. The grade has a letter, which designates the grade, and a number, which designates the minimum yield strength in thousands of psi.
