API Spec 5CT Casing and Tubing

API Spec 5CT Casing and Tubing

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API Spec 5CT Specification for Casing and Tubing, Eighth Edition, Petroleum and natural gas industries-Steel pipes for use as casing or tubing for wells.

The main steel grade of API 5CT:

• API 5CT J55
• API 5CT K55
• API 5CT N80
• API 5CT L80
• API 5CT P110

Casing pipe end thread type

The International Standard specifies the technical delivery conditions for steel pipes (casing, tubing, plain end casing liners and pup-joints) and accessories. It is applicable to the following connections in accordance with ISO 10422 or API Spec 5B:

- short round thread casing (STC);
- long round thread casing (LC);
- buttress thread casing (BC);
- extreme-line casing (XC);
- non-upset tubing (NU);
- external upset tubing (EU);
- integral joint tubing (IJ).

For such connections, this International Standard specifies the technical delivery conditions for couplings and thread protection.
For pipes covered, the sizes, masses, wall thicknesses, grades and applicable end finishes are defined.
It may also be applied to tubulars with connections not covered by ISO/API standards.

Chemical Compositions(%) of API 5CT

Grade	C≤	Si≤	Mn≤	P≤	S≤	Cr≤	Ni≤	Cu≤	Mo≤	V≤	Als≤
API 5CT J55	0.34-0.39	0.20-0.35	1.25-1.50	0.020	0.015	0.15	0.20	0.20	/	/	0.020
API 5CT  K55	0.34-0.39	0.20-0.35	1.25-1.50	0.020	0.015	0.15	0.20	0.20	/	/	0.020
API 5CT N80	0.34-0.38	0.20-0.35	1.45-1.70	0.020	0.015	0.15	/	/	/	0.11-0.16	0.020
API 5CT  L80	0.15-0.22	1.00	0.25-1.00	0.020	0.010	12.0-14.0	0.20	0.20	/	/	0.020
API 5CT J P110	0.26-035	0.17-0.37	0.40-0.70	0.020	0.010	0.80-1.10	0.20	0.20	0.15-0.25	0.08	0.020

Mechanical Properties of API 5CT

Steel Grade	Yield Strength (Mpa)	Tensile Strength (Mpa)
API 5CT J55	379-552	≥517
API 5CT K55	≥655	≥517
API 5CT N80	552-758	≥689
API 5CT L80	552-655	≥655
API 5CT P110	758-965	≥862

For pipes covered by this International Standard, the sizes, masses, wall thicknesses, grades and applicable end finishes are defined.

Oil Country Tubular Goods

Oil Country Tubular Goods (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. (see Figure 1 for schematic of a deep well):

• 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)

• Tubing Pipe - Seamless Steel Tubing manufactured to API 5CT Specification Latest Edition, EUE Threaded and Coupled
• Casing Pipe - Seamless Steel Casing manufactured to API 5CT Specification Latest Edition, Plain End
• Carbon and Alloy Line Pipe, Welded (60” O.D. and greater), Seamless (up to 24” O.D.), High-pressure and Low-temperature; (ASTM A106, API grades X70 and higher)
• API Pipe Couplings