API 5CT is the technical specification covering steel pipes used as casing and tubing in oil and gas wells. The specification covers both seamless and welded varieties, supporting drilling operations and well conveyance systems. Commonly available grades include J55, K55, N80-1, N80Q, L80 and P110, addressing a wide range of well depths and pressure conditions. Casing is supplied with thread configurations such as STC (short thread), LTC (long thread) and BTC (buttress thread) with matching couplings. The product is engineered for downhole service, providing the mechanical strength and dimensional accuracy required to maintain wellbore integrity, support tubing strings, and isolate producing zones from surrounding formations.
Technical specifications
| Standard | API 5CT (EN/DIN/JIS/ASTM/BS/ASME/AISI equivalents) |
| Diameter (mm) | Seamless 1/4"-36"; Welded 21.3-3620 mm |
| Wall thickness (mm) | Seamless 1.25-50 mm; Welded 1.65-65 mm |
| Steel grade | J55, K55, N80, L80, P110 |
| Length (m) | 3-12 m (customizable) |
| Coating | Bright, polished or black; STC/LTC/BTC thread |