No Weld Seam · Greater Reliability
A Complete Wellbore Protection System from Surface to Deep Reservoir
Product Definition & Manufacturing Essence
Seamless casing pipe is a longitudinally weld-free oil country tubular goods. It is manufactured from alloy steel billets through a fully hot-forming process including high-temperature piercing, multi-stand continuous rolling, sizing, and controlled cooling. The metal fiber structure remains continuous and complete throughout the pipe body, with no heat-affected zone.
This fundamental difference gives seamless casing irreplaceable structural integrity and failure safety margin under extreme conditions such as sour media, cyclic loading, high pressure, and high temperature.
Complete Technical Specifications
Dimensions & Lengths
| Parameter | Range |
|---|---|
| Outer Diameter | 60.3 mm to 508 mm |
| Wall Thickness | 1.65 mm to 26.97 mm |
| Lengths | As per customer's requirment |
Steel Grade System (API Spec 5CT 11th Edition)
| Grade | Min Yield (MPa) | Min Tensile (MPa) | Typical Application |
|---|---|---|---|
| J55 / K55 | 379 | 655 | Shallow wells, conductor casing, conventional low-pressure wells |
| N80 | 552 | 689 | Medium-depth wells, water injection, mild corrosive environment |
| L80 | 552 | 655 | Sour gas fields (H₂S), CO₂ corrosive environment |
| P110 | 758 | 862 | Deep wells, high-pressure wells, shale gas horizontal wells |
Key Performance Advantages
No Weld Seam → Eliminates Three Failure Risks
No HAZ → Eliminates the weak link for H₂S Stress Corrosion Cracking (SSC)
No fusion line → Eliminates lamellar tearing risk
No residual welding stress → Prevents premature fatigue failure
Uniform Mechanical Properties in All Directions
The seamless process keeps property variation within 5% among radial, circumferential, and axial directions. In contrast, welded pipes can show 15%~20% variation across the weld zone.
Quality Control System
Full Process Inspection:
| Inspection Item | Method / Standard |
|---|---|
| Chemical Composition | Direct-reading spectrometer, each heat analysis |
| Mechanical Properties | Tensile, impact (0℃/-10℃/-20℃ optional), hardness, flattening, flaring |
| Non-Destructive Testing | 100% Ultrasonic (longitudinal + transverse) + Flux leakage |
| Hydrostatic Test | Per API 5CT, hold time ≥5 seconds |
| Dimension & Thread | Thread gauges, full-body laser diameter measurement |
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