What exactly is OCTG?

Oil country tubular goods (OCTG) is a family of seamless rolled products consisting of drill pipe, casing and tubing subjected to loading conditions according to their specific application. 

• - Drill pipe is heavy seamless tube that rotates the drill bit and circulates drilling fluid. Pipe segments 30 ft (9m) long are coupled with tool joints. Drill pipe is simultaneously subjected to high torque by drilling, axial tension by its dead weight, and internal pressure by purging of drilling fluid. Additionally, alternating bending loads due to non-vertical or deflected drilling may be superimposed on these basic loading patterns.
• - Casing pipe lines the borehole. It is subject to axial tension by its dead weight, internal pressure by fluid purging, and external pressure by surrounding rock formations. Casing is particularly exposed to axial tension and internal pressure by the pumped oil or gas emulsion.
• - Tubing is pipe through which the oil or gas is transported from the wellbore. Tubing segments are generally around 30 ft [9 m] long with a threaded connection on each end.

Typical OCTG manufacturing processes include (all dimensional ranges are approximate)

• - Continuous mandrel-rolling process and the push bench process for sizes between 21 and 178 mm OD.
• - Plug mill rolling for sizes between 140 and 406 mm OD.
• - Cross-roll piercing and pilger rolling for sizes between 250 and 660 mm OD.

These processes typically do not allow the thermomechanical processing customary for the strip and plate products used for welded pipe. Therefore, high-strength seamless pipe must be produced by increasing the alloying content in combination with a suitable heat treatment such as quench & tempering.