Oil tubing are the main parts of the well drilled construction. They are selected for the specific conditions anticipated in a given well. The anticipated production flow rates and economics of the well determine tubing size, which then determines the necessary size of each previous hole and tubular. Once the tubular size and setting depths are determined, the wall thickness and grade of material are then chosen by the well designer to ensure the strength is adequate for the expected loads. API 5CT developed specifications for three different connectors for use as casing tubing joints: External-upset tubing and coupling (Upset tubing),Non-upset tubing and couplings,Integral-joint tubing.

Upsetting is a forging process that makes for a thicker wall on the tube ends. Upset Tubing (EUE) is a long tubing with joint installed in a wellbore to facilitate the extraction of oil and gas. The tubing joints are designed to suit a certain well type, based on the underground conditions and fluids.It acts as a conduit, through which the produced fluids or gas get transmitted from the bottom to the surface. Tubing joint is relatively a single length pipe that can vary in length anywhere from 25 to 30 ft. This ideal length allows easy production as the tubing joint is fitted with threads on both sides and can run down through a well of any depth.

There may be the same material and grades with upsetting tubing and non-upset tubing.The maximum difference between them are the tube end, that is outer diameter. Non-upset tubing refers to the pipe end without the extra thick and straight thread and collar. Non-upset (NUE) tubing is used much less than EUE tubing. The cost of NUE is only slightly less than EUE, and the joint strength is substantially less. The coupling joint diameter of NUE is less than EUE, which offers some advantages when clearance is small. API NUE joints are available in sizes of 1.050 to 4.500 in.