API Tubing is a critical component in the oil and gas industry, manufactured in accordance with the API 5CT standard (American Petroleum Institute Specification for Casing and Tubing).
Tubing is always referred to by its Outside Diameter (OD).
Certified API 5CT Tubing – 100% Inspected for Well Integrity.
API Tubing Functions
Fluid Transport: Acts as a continuous pipe for producing oil and gas or for injecting water/gas into the formation.
Casing Protection: While casing is usually permanently cemented in place, tubing is designed to be replaceable. It prevents formation fluids from corroding or wearing down the casing.
Production Optimization: Choosing the correct tubing diameter optimizes flow velocity and pressure, ensuring sustained production levels.
Tubing Sizes
These are the most frequently used sizes for the primary string that carries oil or gas to the surface.
| Outside Diameter (OD) | OD (mm) | Nominal Weight (lb/ft) | Wall Thickness (in) | Inside Diameter (ID) | Drift Diameter (in) |
| 2-⅜" | 60.33 | 4.60 (NU) | 0.190 | 1.995 | 1.901 |
| 2-⅜" | 60.33 | 4.70 (EU) | 0.190 | 1.995 | 1.901 |
| 2-⅞" | 73.02 | 6.40 (NU) | 0.217 | 2.441 | 2.347 |
| 2-⅞" | 73.02 | 6.50 (EU) | 0.217 | 2.441 | 2.347 |
| 3-½" | 88.90 | 9.20 (NU) | 0.254 | 2.992 | 2.867 |
| 3-½" | 88.90 | 9.30 (EU) | 0.254 | 2.992 | 2.867 |
| 3-½" | 88.90 | 10.20 | 0.289 | 2.922 | 2.797 |
| 4" | 101.60 | 9.50 | 0.226 | 3.548 | 3.423 |
| 4" | 101.60 | 11.00 | 0.262 | 3.476 | 3.351 |
| 4-½" | 114.30 | 12.60 | 0.271 | 3.958 | 3.833 |
| 4-½" | 114.30 | 13.50 | 0.290 | 3.920 | 3.795 |
Macaroni Tubing Size Table (Small Diameter)
Used primarily for chemical injection, workovers, or slim-hole completions.
| Outside Diameter (OD) | Nominal Weight (lb/ft) | Wall Thickness (in) | Inside Diameter (ID) | Drift Diameter (in) |
| 1.050" | 1.14 | 0.113 | 0.824 | 0.730 |
| 1.315" | 1.70 | 0.133 | 1.049 | 0.955 |
| 1.660" | 2.30 | 0.140 | 1.380 | 1.286 |
| 1.900" | 2.75 | 0.145 | 1.610 | 1.516 |
Length Classifications (API Ranges)
Unlike pipes you buy at a hardware store, oilfield tubing comes in three specific length "Ranges":
Range 1: 20 to 24 feet (6.10 – 7.32 m)
Range 2: 28 to 32 feet (8.53 – 9.75 m) - This is the most common standard.
Range 3: 38 to 42 feet (11.58 – 12.80 m)
Connection Types (Threads)
The size also depends on how the pipes are joined:
EUE (External Upset End): The ends of the pipe are forged thicker before threading. This is the industry standard for production.
NUE (Non-Upset End): The threads are cut directly onto the standard wall of the pipe.
Premium Connections: Proprietary threads (like VAM or TenarisBlue) used for gas-tight seals in high-pressure wells.
API 5CT Oil Well Drilling Tube Factory
API Oilfield Tubing Test equipments
API oil country tubular goods Certificate
FAQ
What is the diameter of the oil field pipe?
The diameter of oilfield pipe varies depending on its specific function in the well. Here are the common ranges for the three main types:
Tubing (Production): 2-⅜" to 4-½" (The string that carries oil/gas to the surface).
Casing (Protection): 4-½" to 20" (The outer pipe that lines the wellbore to prevent collapse).
Drill Pipe: 2-⅜" to 6-⅝" (Used to rotate the bit and circulate mud).
Is tubing measured by ID or OD?
Oilfield tubing is measured by its Outside Diameter (OD).
According to API Spec 5CT standards, the "size" of the tubing always refers to the exterior measurement. While the Inside Diameter (ID) is critical for flow calculations and tool clearance, it varies depending on the pipe's wall thickness (weight), whereas the OD remains constant for a specific size.
