Besides casing and tubing, it also includes pup joints, coupling stock, coupling material, and accessory materials, and establishes requirements for three product specification levels (PSL-1, PSL-2, and PSL-3). The requirements for PSL-1 are the basis of this standard.

This page summarizes how API 5CT casing and tubing are specified, including common grades, product specification levels (PSL), and standardized connection types. For product pages with size ranges and typical ends, refer to Steel Casing Pipe API 5CT and OCTG Tubing, API 5CT Tubing. For thread inspection and gauging references aligned with API connections, refer to API Coupling and Threads for Casing and Tubing.

Common Grades

• J55/K55
• N80/N80Q/L80
• C90
• R95/T95
• P110/C110
• Q125

Connections

API 5CT applies to the following connections which comply with API SPEC 5B:
• SC: Short round thread casing
• LC: Long round thread casing
• BC: Buttress thread casing
• NU: Non-upset tubing
• EU: External upset tubing
• IJ: Integral tubing connections

4 Groups of Grade

• Group 1: All casing and tubing in Grades H, J, K, N, and R
• Group 2: All casing and tubing in Grades C, L, M, and T
• Group 3: All casing and tubing in Grade P
• Group 4: All casing in Grade Q

View more information for API Couplings and Connections.

Manufacture

General

According to the API 5CT standard, steel material used for making the pipe billet shall undergo grain refining treatment. This steel shall contain one or more grain refining elements, such as a certain amount of aluminum, niobium, vanadium, or titanium, so that the austenite grains of the steel Grain refinement.

• Pipes supplied shall be manufactured in seamless type or EW type.
• Couplings, coupling stock, and coupling materials shall be seamless.
• Cold-drawn tubing pipe shall be properly heat treated; otherwise, it is not acceptable.
• Casing and tubing attachment materials shall be seamless pipes unless other types are stated on the order.

Casing and Tubing is a kind of OCTG pipe

Heat Treatment

Heat treatment methods for API 5CT casing and tubing are a key factor to differ in each grade. Products requiring heat treatment shall be subjected to full-body and full-length heat treatment. The heat-treated upsetting product should be heat-treated in terms of its full body and full length after upsetting.

A separately heat-treated coupling blank is acceptable. If the finishing temperature is higher than the upper critical temperature of the treated steel and the pipe is air-cooled, it shall be normalized.

in the case of welding type, the weld seam shall be heat treated to a minimum temperature of 540 ℃(1000°F), or a certain treatment method shall be used to make the no untempered martensite structure in the weld.

N80 Type 1 and Type Q

Steel grade N80 type 1 products shall be normalized or normalized and tempered at the option of the manufacturer.
N80Q steel-grade products shall be quenched and tempered.

R95

R95 steel grade shall be quenched and tempered.

L80

When tempered at temperatures below 620 ℃(1150°F), grade L80 grade 13 Cr may be embrittled.

Straightening

R95

R95 casing and tubing shall not be stretched or expanded cold working after final tempering, except for cold working which is necessary for normal straightening and not more than 3% of compression cold working.

M65 and L80

Steel grade M65 and L80 products shall not be cold worked after final heat treatment except for the cold working required for normal straightening.

C90 and T95

C90 and T95 products can be cold-rotated straightened, but the pipe must be heated to a minimum temperature of 480 ℃(1000°F) degrees for stress relief after straightening. Light gag straightening for steel grade C90 and T95 products is allowed if necessary.

C110

If necessary, the product shall be cold-rotated straightened and subsequently stress-relieved at temperatures between 30℃to 55℃ (50°F to 100 °F) below the final specified tempering temperature, or hot-rotated straightened at temperatures not more than 165℃ (300°F) below the final specified tempering temperature. If necessary, it is allowed to do light gag straightening.

Q125

Gag-press straightening or hot-rotating straightening can be performed for straightening, but the temperature at the end of the rotary straightening should not be less than 400 ℃ (750°F) (unless a higher temperature minimum is specified on the order). If the hot rotary straightening method cannot be used, the product can also be cold-rotated straightened, but the stress relief must be performed at 510 ℃ (950°F) after straightening. The product cannot be subjected to stress relief after cold rotary straightening only by agreement between the purchaser and the manufacturer.

Chemical Composition in API 5CT Specification

The product shall comply with the requirements specified in the chemical composition table for the specified steel grade and type. For the C110 steel grade, the manufacturer shall report when the purchaser asks for the lowest and highest ratios of all elements intentionally added to each batch (regardless of the purpose of its addition).

Tensile Properties

The product shall meet the tensile performance requirements specified in this standard. The tensile properties of the upset casing and tubing (except for elongation) shall be consistent with the requirements of the pipe body. In case of any dispute, the properties of the upset area (except for the elongation) shall be determined by cutting the specimen from the upset.

Dimension, Masses, Pipe Ends, and Defects

• API 5CT Casing dimensions and weight chart
• API 5CT Tubing dimensions and weight

For field selection and take-off, dimensional references are often used together with application context. The API tubing and casing chart helps cross-check common tubing ODs against typical casing ODs and connections when the completion requires matched casing-tubing programs.

Labels and Sizes

In the dimensional table of this standard, the pipe is named with the labels and sizes (outer diameter). The outer diameter of the external upset pipe refers to the outer diameter of the pipe body, not the outer diameter of the upset portion.

Dimensions and Masses

The pipe shall be supplied by the sizes, wall thickness and tolerance masses specified in the order. Other plain end pipe sizes and wall thicknesses are available upon purchase and manufacturer agreement. Coupling stock, coupling materials, and accessory materials shall be supplied in the required size of the order or the size of the coupling material shall be as specified in the manufacturer’s internal requirements.

The accuracy of all measuring equipment used for receiving or rejecting shall be verified at least once per operating shift, apart from threaded ring gauges, plug gauges, and weighing implements.

According to the provisions of this standard, if a measuring device that is calibrated or verified is subject to abnormal or severe conditions sufficient to affect its accuracy, it should be re-calibrated or re-verified before further use.

Outside diameter tolerances

The following tolerances apply to the outside diameter, D, of casing and tubing:

For upset integral tubing connection

The following tolerances apply to the outside diameter of the pipe body immediately behind the upset for approximately 127 mm (5.0 in) for sizes Label 1: 5-1/2 and smaller, and a distance approximately equal to the outside diameter for sizes larger than Label 1: 5-1/2. Measurements shall be made with calipers or snap gauges.

Wall thickness

Tolerance for casing and tubing wall thickness is -12.5%.

Products end

Flat-end pipe

Flat-end pipe is a pipe supplied with unmachined threads, and it may be, or not be upset, in whichever case, it shall comply with all requirements of a specific steel grade in this standard.

Product with API Threads

Steel grade H40, J55, K55 or M65 casings are available in short or long threads. However, if the purchaser requests a long-threaded casing, it should be specified in the order.

Rounded Nose

The “round” or “bullet-nose” type of pipe end may be provided by the manufacturer or specified by the purchaser to replace the conventional corner breaks on the threaded ends of external upset tubing. The improved end should be rounded so that the coating is applied and the inner and outer surfaces are rounded and smooth, without sharp corners, or burrs.

Threading

Product threading, gauging practice, and thread inspection shall be in accordance with API Spec 5B. The product end shall not be hammered but may be slightly shaped to meet the requirements of thread machining. For steel grades of C90 and higher strength, such forming shall only be carried out with the consent of the purchaser.

Workmanship of ends

All product ends shall be free of burrs on the inside and outside edges. And sandblasting shall be applied to both male and female threads of C110 steel grade.

Defects

All pipes and fittings made of pipes shall not have the following defects:
a. Any quenching crack
b. Any arc burn
c. Any surface cracking defect that reduces the net effective wall thickness to less than 87.5% of the specified wall thickness can be confirmed.
d. When the non-destructive inspection is specified in this standard or on an order, any non-surface cracking defects on the outer surface having an area greater than 260 mm2 (0.41 in2) are detected.
e. Any non-surface cracking defect that reduces the effective wall thickness to less than 87.5% of the specified wall thickness can be confirmed within 1.6 mm (1/16 in) of both sides of the weld.
f. Any internal upset structure on all upset products may have sharp corners or drastic change of sections that can cause the 90 ° hook type tool to hang up.
g. Any non-linear surface cracking defects on the inner surface of the externally threaded part of the sanitary tube with a depth greater than 10% of the specified wall thickness.

Delivery from Octal

In well construction, casing and tubing are the two primary OCTG strings that define integrity and production flow. Casing is the structural liner that supports the borehole and isolates formations after cementing, while tubing is the retrievable flow conduit installed inside casing. For API-grade selection and standard compliance, refer to API 5CT Casing and Tubing Specification, and for product-level size and connection options, refer to Steel Casing Pipe API 5CT and OCTG Tubing, API 5CT Tubing.

According to the API (American Petroleum Institute) standardized specifications, through the control of the chemical properties and adopting different heat treatments, OCTG pipe is classified into different performances material with more than ten grades.

Types of Oil Country Tubular Goods (OCTG pipes)

There are three main types of Oil Country Tubular Goods, which include Drill pipe, Casing pipe, and Tubing pipe.

To give you a better understanding, we will explain the meaning of each of the three to help you understand their work and their use.

OCTG Drill pipe – Pipe for Drilling

Drill pipe is a heavy, seamless tube that rotates the drill bit and circulates drilling fluid. It allows the drilling fluid to be pumped through the bit and back up the annulus. The pipe can withstand axial tension, extremely high torque and high internal pressure. That is why the pipe is extremely strong and vital in OCTG endeavour.

Drill Pipe normally means the Durable steel pipe used in drilling, standards in API 5DP and API SPEC 7-1.

If you don’t understand the annulus of oil well, it is the space between the casing and the piping or any piping tubing, casing or piping immediately surrounding it. Annulus allows the fluid to circulate in the well. So when we are talking about strong or heavy-duty OCTG pipe, we are talking about Drill pipe.

Steel Casing pipe – Stabilize the wellbore

Steel casing pipe is a type of pipe used in the construction of wells, particularly in the oil and gas industry. It is used to line the borehole that is being dug into the ground to get oil. Just like the drill pipe, the steel pipe casing can also withstand axial tension. This is a large-diameter pipe inserted into a drilled borehole and held into place with cement. The casing is subject to the axial tension of its dead weight, the external pressure of the rock surrounding it, and the internal pressure of the purging fluid. When it is well cemented in place, the drilling process is aided in the following ways:

1. Structural Support: Casing sticks the drill string and prevents unstable upper formation from caving in, provide structural integrity to the wellbore, preventing it from collapsing during drilling and production.
2. Isolation: It prevents water well zone contamination, they isolate different geological formations to prevent the migration of fluids between them. This is crucial for maintaining the integrity of the well and protecting groundwater resources.
3. Protection: Casing provides a smooth internal bore for the installation of production equipment, safeguards the well from external contaminants and environmental factors, and ensures that the extracted resources remain uncontaminated. It also seals off high-pressure zones from the surface, preventing fluid loss in production areas.
4. Facilitating Production: Casing allows for the installation of production tubing and other equipment necessary for extracting oil or gas from the well.

Casing pipes are typically made from steel and come in various sizes and grades, depending on the specific requirements of the well and the conditions it will encounter, it is an extremely heavy-duty pipe vital to OCTG.

Casing and Tubing Manufacturing Video

OCTG Casing Pipe standard

Steel Casing pipe standards usually referred to API 5CT, Common Grades in J55/K55, N80, L80, C90, T95, P110 etc. Common length in R3 which nominal at 40 ft / 12 meters. Casing pipe ends connection types are usually in BTC and LTC, STC. And premium connections are also required in large quantities in an oil and gas piping project.

Steel Well Casing Pipe Price

Steel Casing Pipe cost is lower than drill pipe or the OCTG tubing cost, it is usually higher 200 USD than the regular API 5L pipe. Considering the Threading + Coupling cost or the heating treatment.

OCTG Tubing Pipe – Transporting Oil and Gas to the Surface Ground

OCTG Tubing pipe is a type of pipe used in the oil and gas industry, specifically within wells, to transport fluids (such as oil, gas, or water) from the production zone to the surface. Tubing is the simplest part of OCTG and it is normally found in the segment of 30 ft (9 m), with threaded connections at both ends. The pipe is either used to transport natural gas or crude oil from the producing formation to the facilities where it will be processed after drilling is complete. Here are some key characteristics and functions of tubing pipe:

1. Fluid Transport: Tubing serves as the conduit for the extracted fluids, allowing them to flow from the reservoir to the surface facilities for processing and storage.

2. Smaller Diameter: Tubing pipes typically have a smaller diameter compared to casing pipes, which allows for efficient flow rates and easier handling during installation.

3. Pressure Resistance: Tubing is designed to withstand the pressures encountered during production, ensuring safe and reliable transport of fluids.

4. Installation: Tubing is installed inside the casing and can be easily removed or replaced if necessary, facilitating maintenance and repairs.

5. Production Optimization: The design and material of tubing can be optimized for specific production conditions, enhancing the efficiency of fluid extraction.

This tubing must be able to withstand pressure during the extraction process and adequately resist loads and deformations that have to do with production and workovers. Just like casing is manufactured, tubing is also manufactured the same way, but an additional upsetting process is applied to make it thicker.

OCTG Tubing pipe standard

Same as casing pipe standard, OCTG tubing in API 5CT is also in the same material grades (J55/K55, N80, L80, P110 etc), but the tubing’s diameters are up to 4 1/2”, and it ends in various types such as BTC, EUE, NUE, and premium. Most commonly, thickened connections EUE.

Tubing Seamless Manufacturing Video

How steel casing pipe and tubing work together

OCTG pipe Casing and Tubing Specifications

Casing and Tubing Chemical composition in API 5CT
API 5CT Casing and Tubing Data Sheet Download

Mechanical Properties Tensile Strength and Yield Strength

Features for OCTG pipe

All OCTG pipes have a standard requirement of dependable hardness. So, whether it is OCTG tubing, OCTG pipe or OCTG drill pipe, there is a certain required standard that is always about super hardness. To meet the standard, manganese and chromium are used as the main alloys to confirm cohesion and durability.

There has been recent developments to eliminate sulfide stress cracking, which is the major problem with manganese and chromium. Alloy and Molybdenum are blended together to overcome the chromium and manganese limitations. So OCTG pipes are now harder than ever, and the fear of sulfide stress cracking has been eliminated.

Looking to buy OCTG Pipe with assured quality at a good price?

Unlike in the past when sulfide stress cracking is a major issue, OCTG pipes are now harder than ever before and are well protected against cracking. If you are looking for the best OCTG distributor, look no further because we – one of the most responsible OCTG distributors – are here.

We make sure our drill pipe, casing and tubing are made to the best quality from guaranteed raw steel material, with competitive prices all over China. All the Oil Country Tubular Goods we supply comply with API standards and are under witness inspection from third parties. They can be used for decades to save your cost in the long run.

As a recognized professional manufacturer, supplier, and distributor, we provide a piping solution for oil and gas companies. Contact us for top-quality OCTG pipe today.

OCTG Delivery from Octal