What Is OCTG

OCTG, or Oil Country Tubular Goods, typically refers to seamless pipes with applications in oil. For any pipe to get classified as an OCTG product, it must meet specific conditions. This list includes pipe composition, tensile strengths, transfer conditions, and more. 

This term also includes relevant accessories and also covers welded pipes. Since these products get used in heavy-duty industries, even drills, bumper rings, and tubing/casing must pass the loading conditions criteria to qualify as OCTG.

Oil pipes

OCTG Production And API 5CT Pipes 

For production, OCTG pipes must undergo a continuous rolling process to ensure that they are sufficiently durable for application in oil.

Manufacturers use a mandrel and push bench for pipes with an outer diameter of 21 mm to 178 mm. For larger-sized pipes, the preferred production method is plug mill and Pilger rolling. 

The products made via the two processes display outer diameters of 140 mm to 406 mm and 250 mm to 660 mm, respectively. Manufacturers also prefer using alloys when making these pipes because their Manganese and Chromium content administers resistance and uniformity to the product.

Adding Molybdenum to the alloy also ensures pipe durability, especially when used in drilling. As the pipes are driven deeper into the earth, they face extreme stress due to the pressure there.

Additionally, the drilling process itself makes the pipes prone to corrosion. The inclusion of Moly as an ingredient in alloy pipes counters this effect by helping strengthen the Chromium and Manganese builds.

Top Uses Of OCTG API 5CT Pipes

OCTG covers three major types of pipes, i.e., drilling, casing, and tubing pies. As suggested by their names, each of these plays a crucial application in OCTG projects.

OCTG API 5CT Use In Drilling

Drill pipes typically consist of seamless pipes. Unlike ERW or LSAW pipes, these get made by perforating hollow sections into whole steel billets and ingots. As a result, seamless pipes have no welded area. So, they are less prone to corrosion and more durable and robust. 

These qualities make seamless pipes perfect for use in drilling projects. Drill pipes need to be extremely strong because they get exposed to conditions including: 

  • The purging of the drilling fluid causes high internal pressure.
  • Extreme torque caused by the drilling activities
  • Axial tension is caused by the pipe's dead weight.

These OCTG pipes also have more weight than standard pipes as they are used for rotating drill bits and carrying drill fluids. For longer drill pipes of about 30 feet or more, multiple piping gets fused using piping components like tool joints.

OCTG API 5CT Use In Casing

In oil extraction, once the oil well has been drilled and tapped, you can use a pipe to keep the borehole stable. These pipes that line the drilled hole are OCTG casing pipes, ensuring smooth access to the oil reserves. 

These pipes are also vital for any drilling/oil operation, be it on or offshore. Like drilling, casing pipes are also subject to massive conditional pressure, including

  • Axial pressure caused by the pie's dead weight
  • External pressure exerted by the surrounding sediments and rock formations
  • Internal pressure resulting from oil being pumped through.

OCTG API 5CT Use In Tubing

While the casing pipe ensures access by lining the borehole, the tubing pipe is the OCTG that transports the raw product. They are encased within the casing pipes and the only pipe entering the wellbore.

As in drilling and casing, API 5CT pipes used for this process must be highly resistant to corrosion and pressure as they carry massive amounts of oil to the surface.

Tubing segments are typically around 30 feet and come with threaded ends. These cuttings ensure that each pipe is fitted tightly to the next to avoid product leakage. 

What Is API 5CT

API 5CT is an American Petroleum Institute standard categorized as an OCTG pipe. The outer dimensions of these pipes can reach up to 20 inches, making them apt for casing and tubing application in oil and gas.

Aside from laying down directions for using steel pipes in these industries, API 5CT also includes guides for technical delivery for several pipe components, including joints, stock, and coupling materials. 

API 5CT Pipes Grade Grouping 

  • Group 1 is composed of all tubing and casing under API SCT Grades H, J, K, N, R
  • Group 2 is composed of all tubing and casing under API SCT Grades C, L, M, T
  • Group 3 is composed of all tubing and casing under API SCT Grade P
  • Group 4 is composed of all casing under API SCT Grade Q

API 5CT Pipes: Compatible Couplings 

When compiled with API %B specifications, 5CT pipes are compatible with the following connections:

  • Short Round Thread Casing
  • External Use Tubing
  • Non-Upset Tubing
  • Long Round Thread Casing
  • Buttress Thread Casing 

Top Characteristic Features Of API 5CT Pipes

  • API 5CT pipes have a maximum length of 12000 mm.
  • The wall thickness for these pipes varies from 1.0 mm to 219.0 mm.
  • API 5CT pipes have an outer dimension of 114 to 508 mm.
  • This specification demands that all couplings, stocks, and materials be seamless. 
  • These steel pipes come in grades like J55, K55, N80, P110, and L80.
  • API 5CT pipes are mostly used in the oil and gas industry
  • Under API 5CT specs, casing and tubing pipes are seamless unless specified.

Tensile Properties Of OCTG API 5CT Pipes



 Tensile Strength




Yield Strength










  379 to 552










  379 to 552




  689   552 to 758



655   552 to 655
  P110 862  758 to 965

Chemical Properties Of OCTG API 5CT Pipes


















0.34 to 0.39 


0.34 to 0.38

0.15 to 0.22 


0.26 to 0.35




0.20 to 0.350.20 to 0.35 1.0 0.17 to 0.37



1.25 to 1.50 


1.45 to 1.70

0.25 to 1.0  


0.40 to 0.70



















0.15 0.010  











12.0 to 14.0



8.0 to 1.10




























   0.15- 0.25





0.11 to 0.16