Tubings are screwed together through connections, which could either be:
By means of integral joint (the most common type of connection on small diameter pipe),
Or by using a coupling (the most common connection); a collar with internal threads used to join two sections of threaded pipe.
Selection of tubing connections:
The type of tubing connections selected for a completion will depend mainly on the well characteristics. The connection must be able to contain the produced fluids safely and at the maximum pressures anticipated.
The basic requirements of a tubing string connection are:
Strength compatible with the operational requirements of the string during, and after running;
Sealing properties suitable for the fluid and pressures expected;
Ease of stabbing during make-up, and safe breakout when pulling the tubing;
Resistance to damage, corrosion, and erosion.
Types of thread connection:
There are two types of thread connection: API and Premium.
Tubing is a relatively small-diameter pipe that is run into a well to serve as a conduit for the passage of oil and gas to the field surface facilities for processing. Tubing must be adequately strong to resist loads and deformations associated with production and workovers. Further, tubing must be sized to support the expected rates of production of oil and gas.
Tubing is specified by grade, outer diameter, weight, and connection. API tubing grades correspond to casing grades with the exception that P grade tubing has a tensile strength of 105,000 psi and is referred to as P105.