Oil Country Tubular Goods Line Pipe, OCTG Seamless & Welded Steel Pipe

Oil country tubular goods (OCTG) is a group of seamless rolled products comprising of the casing, tubing, and drill pipe subjected to stacking conditions according to their particular application.

• Drill pipe is heavy seamless tube that circulates drilling fluid and rotates the drill bit. Pipe segments 30 ft (9m) long are combined with tool joints. Drill pipe is at the same time subjected to drilling by its dead weight, high torque by axial tension, and internal pressure by the purging of drilling fluid. Additionally, alternating bending loads due to non-vertical or redirected drilling may be superimposed on these basic loading patterns.
• Casing pipe lines the borehole. It is liable to internal pressure by fluid purging, axial tension by its dead weight, and external pressure by surrounding rock formations. The casing is especially exposed to axial tension and internal pressure by the pumped oil or gas emulsion.
• Tubing is the 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 association on each end.

Corrosion resistance under sour service conditions is a very important OCTG characteristic, especially for casing and tubing. Typical OCTG suppying processes include (all dimensional ranges are approximate)

• Continuous mandrel-rolling process and the push bench process for sizes somewhere in the range of 21 and 178 mm OD.
  
• Plug mill rolling for sizes somewhere in the range of 140 and 406 mm OD.
• Cross-roll piercing and Pilger moving for sizes somewhere in the range of 250 and 660 mm OD.

These procedures normally don't allow the thermomechanical processing customary for the strip and plate products used for welded pipe. In this way, the high-quality seamless pipe must be delivered by increasing the alloying content in combination with a suitable heat treatment such as quench & tempering.