Manufacturing & Standards
To ensure absolute reliability and safety under extreme downhole conditions (high pressure, tension, torsion, and corrosive environments), oil steel pipes are manufactured to stringent international specifications. The predominant standard is the API 5CT (American Petroleum Institute Specification for Casing and Tubing), which rigorously defines the chemical composition, mechanical properties, and dimensional tolerances . In addition to API standards, specific applications may require adherence to proprietary specifications, such as the Russian GOST 633-80 standard or national GB standards, depending on regional requirements .
Modern oil steel pipes are often produced using seamless processes (such as plug mill rolling or mandrel rolling) to maximize structural integrity and pressure resistance. However, high-frequency induction (HFI) welded pipes are also available for less critical applications or specific dimensional requirements . For extreme environments—such as sour service (H₂S) wells, high-pressure deep wells, and offshore operations—premium grades and proprietary corrosion-resistant alloys (e.g., 13Cr stainless steel) are utilized
| Category | Parameter | Specifications / Range |
| Standards | Design & Testing | API 5CT, API 5B (Threading), API 5DP (Drill Pipe) . |
| Casing Pipe | OD: 4.5" – 20" (114.3 mm – 508.0 mm) .
Grades: J55, K55, N80, L80, P110, C90, T95, Q125 . |
| Tubing Pipe | OD: 1.05" – 4.5" (26.7 mm – 114.3 mm) .
Grades: J55, N80, L80, P110 . |
| Dimensions & Size | Drill Pipe | OD: 2.375" – 6.625" .
Grades: E75, X95, G105, S135 . |
| Wall Thickness | Typically ranges from 0.113" (2.87 mm) to 0.514" (13.06 mm) . |
| Length Range | Generally supplied in R2 (27-30 ft) or R3 (38-45 ft) . |
| Mechanical Properties (Typical) | Grade J55/K55 | Yield Strength: 55,000 psi (379 MPa) min.
Tensile Strength: 75,000 psi (517 MPa) min . |
| Grade N80 | Yield Strength: 80,000 psi (552 MPa) min.
Tensile Strength: 100,000 psi (689 MPa) min . |
| Grade P110 | Yield Strength: 110,000 psi (758 MPa) min.
Tensile Strength: 125,000 psi (862 MPa) min . |
| Connections | API Connections | STC (Short Round Thread), LTC (Long Round Thread), BTC (Buttress Thread Coupling), NUE/EUE (Non-upset/External Upset End) . |
| Premium Connections | Proprietary designs offering enhanced torque, gas-tight sealing, and high structural integrity for complex well profiles (e.g., VAGT, VAsuperior) . |
| End Finishes & Coating | Ends | Plain end, beveled end (for welding), or threaded with couplings . |
| Surface Treatment | Bare, black varnish, oil finish, or anti-corrosion coatings (e.g., 3PE, epoxy, cement mortar) . |
