Steel Pipe & Tube & Petroleum Steel Pipe,J55、N80、L80、P110、B、X42、X52、X65、X70、X80
Detailed Description of Petroleum Tubing
Petroleum tubing (OCTG) is the core pipe material for oil and gas exploration and development, mainly including casing, tubing, drill pipe and line pipe. It is required to withstand high pressure, high temperature and resist corrosion and collapse. The main applicable standards are API 5CT/5L and national standard GB/T 19830.
1. Product Classification & Main Applications
1.1 Casing
Function: Support well walls, isolate formations, prevent well collapse and fluid pollution. It is a one-time consumable, accounting for over 70% of total OCTG consumption.
Classification by application:
Conductor: The outermost pipe to fix the wellhead.
Surface Casing: Seal off shallow water layers.
Intermediate Casing: Adapt to complex formations and high-pressure zones.
Production Casing: Form the permanent flow channel for oil and gas.
Specifications: Outer diameter 114.3–508mm, wall thickness 6.98–22.23mm, standard length 8–12m.
1.2 Tubing
Function: Run inside casing to transport oil and gas to the ground; reusable for operation.
Specifications: Outer diameter 60.3–114.3mm, wall thickness 4.83–9.52mm, length 6–12.5m.
Common Steel Grades: J55, N80, L80, P110; High-performance grades: C90, T95, Q125 (high collapse resistance & sulfide resistance).
1.3 Drill Pipe
Function: Connect drill bits, transmit torque and circulate drilling mud; repeatedly usable.
Specifications: Outer diameter 60.3–168.3mm. Common steel grades: E75, X95, G105, S135.
1.4 Line Pipe
Function: Long-distance transportation of crude oil and natural gas, manufactured in accordance with API 5L.
Common Steel Grades: B, X42, X52, X65, X70, X80 (high-strength for main pipelines).
2. Materials & Steel Grades (API 5CT)
2.1 Carbon Steel & Low Alloy Steel (Mainstream)
J55: For shallow wells with low pressure, cost-effective.
N80: For medium and deep wells, balanced strength and toughness.
L80: Excellent resistance to hydrogen sulfide, preferred for sour service environments.
P110: High strength, applied to deep wells and high-pressure wells.
Q125: Ultra-high strength, suitable for ultra-deep wells and scenarios requiring high collapse resistance.
2.2 Corrosion-Resistant Alloys (High-end)
13Cr / Super 13Cr: Resist carbon dioxide corrosion, for high-temperature sour wells.
Nickel-based Alloy (Inconel 718): Resist combined corrosion of hydrogen sulfide, carbon dioxide and chloride ions, widely used in offshore wells and high-sulfur wells.
3. Applicable Standards
API 5CT: Global standard for casing and tubing, with three quality levels PSL1/PSL2/PSL3 (PSL3 is the strictest).
GB/T 19830: Chinese national standard equivalent to API 5CT. The 2023 version enhances low-temperature impact performance (-40℃) and yield-to-tensile ratio (1.05–1.30).
API 5L: Standard for line pipes, corresponding to Chinese standard GB/T 9711.
NACE MR0175: Standard for sulfide stress cracking resistance, for anti-sulfur pipes.
4. Key Technical Parameters
4.1 Mechanical Properties (API 5CT)
Yield Strength: J55: 379–552MPa; P110: 758–965MPa.
Tensile Strength: No less than 1.05 times of yield strength to avoid brittle fracture.
Impact Toughness: Longitudinal impact energy ≥ 47J at -40℃.
Hardness: ≤ 22HRC (for sour service pipes, to prevent sulfide stress cracking).
4.2 Thread Types
Standard API Threads: STC (Short Round Thread), LTC (Long Round Thread), BTC (Buttress Thread).
Premium Special Threads: Excellent air tightness and torque resistance, such as VAM TOP, BGC, TP-CQ, for high-pressure gas wells.
5. Manufacturing Process
Seamless Pipe (Main Type): Round billet → Heating → Piercing → Hot Rolling → Sizing → Heat Treatment (Normalizing / Quenching & Tempering) → Thread Machining → Non-destructive Testing → Hydrostatic Pressure Test.
Welded Pipe (For Low-pressure Service): Steel strip forming → Submerged Arc Welding → Heat Treatment → Finishing, applied to shallow low-pressure wells.
6. Quality Control
Chemical Composition: Strictly control carbon, silicon, manganese, phosphorus, sulfur and alloy elements including chromium, molybdenum and nickel.
Non-destructive Testing: Ultrasonic Testing (UT), Magnetic Flux Leakage (EMI), Magnetic Particle Testing (MT) to detect internal and external defects.
Hydrostatic Pressure Test: Hold pressure for no less than 10 seconds as required by standards, no leakage allowed.
Dimension & Appearance: Wall thickness tolerance ±12.5%, ovality ≤1%; Thread accuracy complies with API 5B.
7. Application Scenarios
Conventional Wells: J55 / N80, for shallow to medium-deep wells without corrosion.
Deep & High-pressure Wells: P110 / Q125, for wells over 3500m with high collapse resistance requirement.
Sour Wells (H₂S contained): L80 / 13Cr, for sulfur-bearing formations to avoid stress cracking.
Offshore & High-temperature Wells: Super 13Cr / Nickel-based Alloy, for severe corrosion and high temperature conditions.
Long-distance Transmission Pipelines: X70 / X80, for national trunk pipelines.
8. Packaging & Marking
Packaging: Bundled with anti-rust film; thread protectors installed at both ends.
Marking: Steel grade, dimensions, standard number, heat number, manufacturer and production date.
9. Certificates & Lead Time
Certificates: API monogram certificate, material test report, non-destructive testing report, hydrostatic test report, NACE certificate (if required).
Lead Time: 30–45 days for standard seamless pipes; 45–60 days for pipes with special threads.
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