SY/T 0135
Technical Overview: SY/T 0135-2000 – Petroleum Industry Standard for Seamless Casing Pipe (Withdrawn/Replaced)
1. Definition
SY/T 0135-2000 specified the technical requirements, testing methods, inspection rules, marking, and packaging for seamless steel casing pipes used in petroleum and natural gas drilling and production. It primarily governed pipes manufactured within China for domestic use, establishing quality benchmarks for mechanical properties, dimensions, tolerances, testing, and performance under downhole conditions (pressure, collapse, tension).
2. Product Scope & Applicability
Product Type: Seamless steel casing pipes.
Primary Application: Oil and gas well drilling and completion for:
Isolating formation zones.
Preventing wellbore collapse.
Providing a conduit for production tubing and downhole equipment.
Containing wellbore pressure.
Service Environment: Designed to withstand downhole stresses including internal/external pressure, axial tension, compression, collapse forces, and corrosive wellbore fluids (requiring specific material grades).
3.Steel Grades & Material Requirements
SY/T 0135-2000 defined casing grades primarily based on minimum yield strength and heat treatment:
| Grade | Type | Min. Yield Strength (MPa) | Min. Tensile Strength (MPa) | Hardness (HRC) Max | Primary Application |
| H40 | Non-Alloy | 276 | 414 | – | Shallow, low-pressure wells. |
| J55 | Non-Alloy | 379 | 517 | 25.4 | General purpose, moderate depth/pressure. |
| K55 | Non-Alloy | 379 | 655 | 25.4 | General purpose (similar to J55, higher tensile). |
| N80 | Non-Alloy¹ | 552 | 689 | 35.5 | Deeper wells, higher pressure. |
| N80Q | Quenched & Tempered | 552 | 689 | 35.5 | Enhanced toughness for demanding conditions. |
| L80 | Alloy (Cr) | 552 | 655 | 23 | Corrosion resistance (sweet/sour). Type 1, 9Cr, 13Cr. |
| C90 | Alloy (Cr) | 621 | 689 | 35.5 | High strength, corrosion resistance (sour). |
| T95 | Alloy (Cr) | 655 | 724 | 35.5 | Very high strength, corrosion resistance (sour). |
| P110 | Quenched & Tempered | 758 | 862 | 42 | Very deep, high-pressure wells. |
¹ N80 could be normalized or Q&T. N80Q specifically required Q&T.
Chemical Composition: Specified maximum limits for Carbon (C), Manganese (Mn), Phosphorus (P), Sulfur (S), Silicon (Si), and alloying elements (e.g., Chromium (Cr), Molybdenum (Mo)) depending on the grade (especially for L80, C90, T95). Composition aimed to achieve the required mechanical properties and suitability for the intended service environment (e.g., sour service grades had stricter limits on hardness and P/S content).
Heat Treatment: Mandatory for grades like N80Q, L80, C90, T95, P110 to achieve specified strength and toughness. Other grades (H40, J55, K55, N80) could be supplied in the as-rolled or normalized condition if meeting properties.
4. Dimensions & Weight
Outside Diameter (OD): Covered a common range for casing, typically starting from around 114.3 mm (4 ½ in) up to 508.0 mm (20 in) or larger. Specific sizes were listed in detailed tables within the standard.
Wall Thickness (WT): Varied significantly based on OD and specified pipe weight/grade. Ranged from approximately 5.2 mm (0.205 in) for smaller OD light-wall pipe to over 16 mm (0.630 in) for larger OD heavy-wall pipe.
Weight: Specified as nominal weight per unit length (kg/m or lb/ft). Each OD/WT combination had a designated nominal weight. Tolerances on weight were provided.
Length: Specified ranges for:
Range 1: 4.88m – 7.62m (16ft – 25ft)
Range 2: 7.62m – 10.36m (25ft – 34ft)
Range 3: > 10.36m (> 34ft)
Tolerances on specified length were defined.
5. Dimensional & Geometric Tolerances
Key tolerances included:
| Parameter | Tolerance Specification (Typical Examples – Refer Standard for Exact Values) |
| Outside Diameter | Specified ± percentage or fixed value (e.g., ±0.75% or ±1.0% of nominal OD, depending on size/process). Ovality limits also applied. |
| Wall Thickness | Specified ± percentage (e.g., -12.5% / + varies). Minimum WT at any point must not fall below nominal minus tolerance. Eccentricity limits. |
| Weight | Single Pipe: -3.5% to + varies %. Lot Average: ≥ Nominal Weight. |
| Length | + 0 / + 152 mm (0 / +6 in) for specified cut lengths. Tighter for threads requiring coupling makeup. |
| Straightness | Maximum deviation: ≤ 0.2% of pipe length. |
| Threads & Couplings | Strict tolerances on thread form (V-shaped, round), pitch, taper, lead, height, truncation as per API Spec 5B referenced profiles. Crest/root checks. |
6.Testing Requirements
SY/T 0135-2000 mandated rigorous testing:
Hydrostatic Test:
Mandatory for every pipe.
Minimum test pressure calculated based on specified wall thickness (t), specified minimum yield strength (SMYS), and OD (D): P = 2 * SMYS * t / D * F
F = 0.5 for H40/J55/K55; F = 0.8 for N80/N80Q/L80/C90/T95/P110.
Pressure held for ≥ 5 seconds. No visible leakage permitted.
Tensile Test:
Performed on samples representing each heat treatment lot.
Measured Yield Strength (0.2% offset or 0.5% TE), Tensile Strength, Elongation.
Results must meet or exceed the minimums specified for the grade (See Table above).
Hardness Test:
Performed (usually Brinell or Rockwell) on samples from each heat treatment lot.
Values must conform to grade-specific maximums (See Table above). Critical for sour service grades.
Impact Test (Charpy V-Notch):
Mandatory for grades P110, T95, C90, L80 (Types 1 & 9Cr).
Required minimum average energy and individual values at specified temperature (often 0°C or -20°C depending on grade/designation).
Flattening Test:
Performed on pipe ends (or samples) from each heat treatment lot for grades H40 to K55 and N80 (non-Q&T).
Pipe section flattened to a specified distance (H) between plates without cracking. H = (1 + e) * t / (e + t/D) where e is a strain factor (e.g., 0.08 for J55/K55).
Drift Test:
Mandatory for every pipe.
A cylindrical mandrel of specified diameter (based on pipe ID and coupling type – API drift sizes referenced) must pass freely through the pipe under its own weight.
Non-Destructive Testing (NDT):
Ultrasonic Testing (UT): Required for all grades except H40. Covered the full body length to detect longitudinal imperfections exceeding reference standards.
Magnetic Particle Inspection (MPI) or Eddy Current (EC): Used for inspecting the pipe ends (after threading) for surface imperfections.
Visual Inspection: Every pipe examined internally and externally for surface defects exceeding allowed limits.
Gauging: Threads and couplings verified using API master gauges (Ring & Plug gauges) per API Spec 5B requirements referenced by the standard.
Dimensional Inspection: Verification of OD, WT, length, straightness, thread dimensions.
7. Marking & Packaging
Pipes required permanent marking indicating: Manufacturer, SY/T 0135-2000, Grade, Size (OD & Weight per unit length), Heat Number, Inspection Mark, and potentially length range.
Thread protectors were mandatory for pipe ends and couplings.
Packaging aimed to prevent damage during transport and storage.
Conclusion & Key Consideration
SY/T 0135-2000 served as a critical national standard in China, establishing comprehensive technical requirements for seamless casing pipes during its active period. It covered essential aspects from material chemistry and mechanical properties to dimensional tolerances, rigorous testing protocols, and inspection criteria.
However, crucially, SY/T 0135-2000 is obsolete. It has been formally replaced by SY/T 0135-2017, which incorporates significant updates and aligns more closely with globally recognized API standards like API 5CT. For any current project, specification, or procurement activity involving casing pipes intended for oil and gas service, SY/T 0135-2017 or API 5CT (potentially with supplemental requirements) must be the referenced standards. Always verify the exact, applicable standard required for your specific application. Using a withdrawn standard like SY/T 0135-2000 carries significant technical and compliance risks.
