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Help CenterSteel Pipe & Tube & OCTG Oil Country Tubular Goods，H40、J55、K55、M65、N80-1、N80Q、R95、L80-1、L80-9Cr、L80-13Cr、Gr.B、X42、X52、X60、X65、
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1. Product Definition & Core Overview
Petroleum steel pipe, also known as OCTG (Oil Country Tubular Goods), is a series of high-strength, high-pressure and corrosion-resistant special steel pipes dedicated for onshore and offshore oil & gas exploration, drilling, completion, production and long-distance transmission. Mainly manufactured from high-quality carbon-manganese steel and low-alloy steel via seamless rolling or precision welding process, it is structurally divided into drill pipe, casing, tubing and line pipe.
Different from ordinary industrial pipes, petroleum steel pipes are designed to adapt to extreme downhole working conditions including deep well high pressure, high temperature, hydrogen sulfide corrosion, chloride salt erosion and formation extrusion. It features high tensile strength, excellent low-temperature toughness, anti-sulfide stress cracking performance and stable structural rigidity, ensuring long-term safe operation in sour oilfields, ultra-deep wells and marine oil & gas projects.
2. Executive Standards & Product Classification
2.1 Core International & Domestic Standards
International API Core Standards (Oilfield Universal)
API Spec 5CT: Casing and Tubing for oil and gas wells (the most authoritative standard for downhole pipes)
API Spec 5L: Line pipe for crude oil and natural gas long-distance transmission (PSL1 / PSL2 grade)
API Spec 5DP: Drill pipe for petroleum drilling engineering
NACE MR0175: Anti-sulfur corrosion standard for sour oilfield pipes
Chinese National & Industry Standards
GB/T 9711: Steel line pipe for petroleum and natural gas industry
GB/T 19830: Seamless steel casing and tubing for oil wells
SY/T 6276: Oil and gas pipeline safety evaluation standard
GB 9948: Seamless steel pipe for petroleum cracking
2.2 Professional Product Classification
By Oilfield Usage (Core Four Categories)
Oil Casing: The outer protective pipe of oil wells, fixed in well wall to prevent collapse, isolate water layer and gas layer, bear formation pressure, serving as the main structural support of oil wells.
Oil Tubing: Inner pipe for oil and gas production and water injection, used for medium lifting and downhole operation channels, featuring high sealing and fatigue resistance.
Drill Pipe: Special pipe for drilling operation, connecting drill bit and ground equipment, bearing torsion, tension and impact load during drilling.
Line Pipe: Long-distance transmission pipe for surface crude oil, natural gas and produced water, including seamless, ERW and LSAW welded pipes.
By Manufacturing Process
Seamless Petroleum Pipe: Integral piercing and rolling, no welding seam, high pressure resistance, for downhole casing, tubing and high-grade line pipe
ERW Electric Resistance Welded Pipe: High dimensional accuracy, cost-effective, for medium and low-pressure gas transmission pipelines
LSAW Longitudinal Submerged Arc Welded Pipe: Large diameter, thick wall, high structural stability, for long-distance trunk pipelines
By Working Condition Performance
Conventional petroleum pipe, low-temperature resistant pipe, sulfur-resistant anti-corrosion pipe, high-strength deep well pipe, high-pressure cracking pipe
3. Main Steel Grades & Applicable Working Conditions
3.1 OCTG Downhole Pipe Grades (API 5CT)
J55 / K55: Conventional shallow well casing and tubing, cost-effective, suitable for conventional pressure and non-corrosive common oil and gas wells
N80 (N80-1 / N80-Q): Universal medium-strength oil pipe, widely used in medium-depth oil and gas wells, with balanced strength and toughness, suitable for most conventional oilfield development
L80: Standard sulfur-resistant grade, compliant with NACE anti-sulfur standard, dedicated for H₂S-containing sour oil and gas wells to prevent sulfide stress cracking
T95: High-strength anti-corrosion pipe, stable performance in high-pressure and medium-corrosion deep wells
P110: Ultra-high strength petroleum pipe, applicable for ultra-deep wells, high-pressure wells and heavy-load well conditions, with excellent collapse resistance and tensile performance
3.2 Drilling Pipe Grades (API 5DP)
E75, X95, G105, S135: Gradually increased strength grades, suitable for conventional drilling, deep well drilling and ultra-deep well high-torsion drilling operations respectively
3.3 Transmission Line Pipe Grades (API 5L)
X42, X52, X60, X65, X70, X80: Gradient high-strength line pipe series, X70/X80 mainstream for long-distance national trunk oil and gas pipelines, with high toughness and weldability
3.4 High-Temp Cracking Pipe Grades
15CrMo, Cr5Mo, 12Cr1MoVG: Special alloy petroleum cracking pipes for refinery high-temperature heating furnaces and catalytic cracking units
4. Core Mechanical Performance Parameters
4.1 Typical Mechanical Properties
Yield Strength: 379~862MPa (graded by J55→P110)
Tensile Strength: ≥517~931MPa
Elongation: ≥12%~18%, excellent impact toughness, resistant to downhole impact and extrusion deformation
Low-temperature toughness: Meet -29℃ / -45℃ low-temperature impact requirements for cold region oilfield projects
Anti-collapse & anti-extrusion: High wall rigidity, resistant to formation collapse and external pressure in deep wells
4.2 Pressure & Inspection Standards
Hydrostatic Test: 100% full-piece pressure test, test pressure up to 20~70MPa according to different wall thicknesses, stable pressure without leakage or deformation
NDT Inspection: 100% ultrasonic testing + eddy current testing, eliminating internal and external defects such as cracks, inclusions and delaminations
Thread Detection: All threaded pipes adopt precision thread gauges for full inspection to ensure sealing accuracy and connection strength
5. Specification Range & API Standard Length
5.1 Size Range
Outer Diameter: 2-3/8" ~ 20" (60.3mm ~ 508mm), full oilfield common specifications
Wall Thickness: 3.5mm ~ 25.4mm, including standard wall, thickened wall and special heavy wall for high-pressure wells
5.2 API Standard Length Range
R1: 18 ~ 22 ft (5.5 ~ 6.7m)
R2: 27 ~ 30 ft (8.2 ~ 9.1m) — mainstream factory length
R3: 38 ~ 42 ft (11.6 ~ 12.8m) — ultra-long special length
5.3 Thread Types
NU (Non-Upset): Plain end tubing, for conventional shallow and medium wells
EU (External Upset): External thickened thread, higher connection strength and sealing performance, widely used in production wells
Premium Connection: Special high-precision buckle, zero leakage, anti-fatigue, for high-pressure deep wells and offshore platforms
6. Production Process Flow
High-quality steel billet inspection → constant temperature heating → piercing & rolling → sizing & straightening → heat treatment (normalizing / quenching & tempering) → pipe end threading / upsetting → thread precision processing → non-destructive testing → hydrostatic pressure test → dimensional re-inspection → surface anti-rust treatment → thread protector installation → bundling & warehousing
The whole process adopts oilfield special heat treatment technology to ensure uniform metallographic structure, eliminate residual stress, and avoid thread tripping, pipe body deformation and stress corrosion in downhole service.
7. Core Product Advantages
High Downhole Pressure Resistance & Collapse Resistance: Graded high-strength steel design, able to resist ultra-high formation pressure and rock extrusion in deep and ultra-deep wells, effectively preventing pipe collapse and fracture.
Professional Sulfur & Corrosion Resistance: L80 and special anti-corrosion grades effectively resist hydrogen sulfide, carbon dioxide and chloride ion erosion, solving the failure problem of ordinary pipes in sour oil and gas fields.
Excellent Thread Sealing & Connection Stability: API standard thread and premium buckle ensure high air tightness, no leakage under long-term high-pressure alternating load, suitable for downhole dynamic working conditions.
Superior Low-Temperature & High-Temperature Stability: No cold brittleness in low-temperature environments, no creep deformation under long-term high-temperature downhole conditions, adapting to extreme oilfield climates and working conditions.
High Fatigue & Torsion Resistance: Drill pipes and high-grade casing pipes withstand frequent torsion, tension and vibration loads during drilling and production, with long service life.
Full Standard Compliance & Traceability: Fully compliant with API and NACE international standards, complete inspection documents, supporting global oilfield project bidding and acceptance.
8. Main Application Fields
Onshore & Offshore Oil & Gas Drilling: Well body casing, production tubing, drilling drill pipe for conventional oilfields, deep wells and offshore platform wells
Sour Oilfield Development: H₂S and CO₂ containing gas fields, sulfur-containing crude oil wells, requiring anti-corrosion and anti-stress cracking performance
Long-Distance Oil & Gas Transmission: Crude oil trunk pipelines, natural gas transmission pipelines, urban gas pipeline networks
Refining & Petrochemical Units: Petroleum cracking furnaces, heating pipelines, high-pressure reaction and transmission pipelines
Special Oilfield Operations: Water injection wells, acid fracturing wells, thermal recovery heavy oil wells, high-pressure gas storage wells
9. Installation & On-Site Operation Specifications
Thread connections shall be coated with special petroleum thread grease, and torque shall be strictly controlled according to API standards to avoid over-tightening or loose sealing.
Anti-corrosion casing and tubing shall be stored in a dry environment, avoiding long-term open-air damp stacking to prevent surface rust and thread damage.
For sulfur-containing well conditions, matching anti-sulfur pipe fittings and tools must be used to avoid galvanic corrosion.
After pipeline laying and well completion, strict pressure test and air tightness test shall be carried out before putting into production.
Welded line pipes need professional welding process evaluation, with strict pre-heating and post-weld heat treatment to ensure weld toughness.
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