API 5CT casing for oil and gas wells
J55, K55, N80, L80, P110 by inquiry
OD, wall, length and connection matched
MTC and agreed inspection records
COO and export documents by contract
Oil casing is the steel pipe string installed in a drilled well to support the borehole and form part of the well's pressure and zonal-isolation system. Depending on the casing program, a well can use conductor, surface, intermediate, production or liner strings. Casing selection must account for installation loads, cementing, expected pressures, fluids, temperature and service life.
GDD Metal coordinates OCTG casing supply against your approved well design and purchase specification. Send the outside diameter, nominal mass or wall thickness, grade, length range, connection, quantity and destination so we can check the matching mill route and document package. The photograph on this listing illustrates threaded casing with couplings; it does not establish a particular grade or certification.
| Product | Oil and gas well casing / OCTG; pipe body, coupling and thread specification agreed as one item |
|---|---|
| Standards | API Spec 5CT or ISO 11960, with edition and amendments named in the order; API Spec 5B for applicable API thread form and gauging |
| Grades for inquiry | J55, K55, N80, L80, P110 and other applicable grades, subject to mill capability and well-service review |
| Typical OD examples | 4-1/2 in (114.3 mm), 5-1/2 in (139.7 mm), 7 in (177.8 mm), 9-5/8 in (244.5 mm), 13-3/8 in (339.7 mm); size availability by exact grade and mass |
| Wall and length | Nominal mass, wall, tolerance and R2/R3 length range or approved cut length per the ordered standard and mill offer |
| Connections | STC, LTC or BTC where applicable; proprietary premium connections only with confirmed availability, licensing and qualification |
| Manufacturing route | Seamless or permitted welded route as required by grade, standard and purchase specification; never substitute without approval |
| Inspection | Chemistry, mechanical tests, dimensions, NDT, hydrostatic test, drift, thread gauging and coupling checks as applicable to the agreed specification |
| Surface and packing | Temporary rust protection, thread compound if specified, thread protectors, traceable markings, secure bundles and seaworthy loading plan |
| Documents | Mill test certificate and agreed inspection records; certificate of origin, invoice, packing list, bill of lading and export license where legally required |
These are inquiry options and OD examples, not a stock promise. The exact grade-size-mass-connection combination and inspection scope must be confirmed by the mill, contract and MTC.
Oil casing itself is commonly made from carbon or low-alloy steel. The distinction is its well-service specification: an agreed OCTG grade, controlled pipe body, collapse and pressure design, compatible couplings and threads, drift clearance, testing and traceability. A general ASTM A106 seamless pipe or API 5L line pipe is purchased for a different service and cannot be relabeled as API 5CT casing.
Galvanizing adds zinc for atmospheric corrosion protection. It does not provide the specified casing grade, threaded-joint performance, collapse resistance or sour-service qualification. See our general seamless pipe and galvanized round pipe pages when the application is surface piping, fabrication or outdoor structures rather than well casing.
Engineering selection considers axial tension during running and service, internal burst pressure, external collapse pressure, combined loads and the required drift diameter. A stronger grade alone does not solve an undersized wall, unsuitable connection or weak collapse design. The well engineer should calculate the required safety factors from the actual load cases, including cementing and pressure tests.
Confirm whether the project accepts an API standard connection such as STC, LTC or BTC, or requires a qualified premium connection. Thread form, coupling, make-up procedure, torque and protector design affect installation and sealing; a pipe-body MTC does not certify a proprietary connection.
Specify the anticipated H2S, CO2, chlorides, water phase, pH, temperature and pressure where relevant. For an H2S-containing environment, review material and hardness limits against ISO 15156 / NACE MR0175 and the operator's actual service conditions. An L80 grade name by itself is not an unconditional sour-service approval. Higher temperature, corrosive brines and long exposure can require additional material selection, coating or corrosion-control measures.
Middle East: Many buyers start with API 5CT and then add the national oil company's or operator's approved-vendor list, connection, traceability and inspection rules. Hot wells and possible sour environments can make H2S data, heat treatment, hardness and corrosion assessment decisive. These are project conditions, not one universal Middle East grade.
North America: API 5CT is a common purchasing baseline. Onshore and offshore operators may add casing design loads, connection qualification, thread inspection, heat and lot traceability, third-party checks and destination-specific import rules. Agree whether an API Monogram is contractually required and verify the actual manufacturing facility's license; a statement of dimensional conformity is different from Monogram authorization.
Europe: Projects may specify ISO 11960 or a national adoption such as EN ISO 11960 alongside an operator's technical requirements. Offshore projects may impose additional environmental, corrosion, connection, inspection and documentation requirements. Specify the exact standard edition and purchaser supplement rather than relying on a generic "European standard" label.
Africa: API 5CT or ISO 11960 is frequently used as an international procurement reference, while the oil company, well environment and importing country set the detailed checks. Ask early about third-party inspection, certificates, port handling, inland transport limits and thread protection. Country and operator requirements must be confirmed individually.
Surface casing for an onshore drilling contractor: The buyer sends its casing program with OD, mass, grade, R2 length and BTC connection. We seek a matching mill offer and agree thread inspection, drift and bundle markings before production.
Production string for a potentially sour gas well: The operator supplies H2S and other service conditions, load cases, connection requirements and its material specification. A suitable grade and the ISO 15156 qualification route are reviewed before any price or sour-service claim is finalized.
Mixed-size export order for a distributor: The purchase list separates grades, sizes and connections by line item. Heat and bundle identification, individual MTCs, thread protectors and container loading photographs are agreed to support arrival checks. These are sample workflows, not claims about named customers or achieved field results.
For the confirmed supply, request a traceable MTC showing the relevant heat or lot identity and contracted test results. Depending on the standard and purchase specification, the inspection plan may cover chemistry, tensile properties, dimensions, NDT, hydrostatic testing, drift, threads and coupling fit. Third-party inspection can be coordinated against an agreed scope. An EN 10204 3.1 certificate can be requested where the mill can issue it for the contracted product.
Export packages can include the MTC, certificate of origin, commercial invoice, packing list, bill of lading and customs documents. An export license is provided where the applicable goods and destination legally require one. Confirm document wording, legalization or buyer-specific forms before order placement. Bundles should protect coupling faces and threads during sea freight and inland handling.
No. They address different products and acceptance requirements. Obtain approval from the well designer and purchase against the specified casing standard.
No. Select grade with pipe dimensions, connection, load cases, temperature and corrosion exposure. Higher strength does not automatically provide better sour-service performance.
No. Define the actual sour environment and assess the specified material, hardness and qualification evidence against ISO 15156 / NACE MR0175 and the operator's requirements.
If a Monogrammed product is required, we must confirm an appropriately licensed manufacturing facility and the product's marking and records for the order. Do not assume that every API 5CT-conforming offer carries an API Monogram.
Send the casing schedule or MTO with standard edition, grade, OD, nominal mass or wall, length range, end connection, quantity per line, service conditions, inspection requirements, destination port and required documents. Share the approved operator specification if one applies.
Send your casing schedule and destination. GDD Metal will review the supply route, available mill documentation, inspection scope, thread protection and export packing against the exact order.
Contact GDD Metal for a project quotation.
