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Understanding API TR 2572-2013: Carbon Steel Casing and Tubing for Non-Corrosive Service
A comprehensive guide to the API Technical Report covering material selection, manufacturing guidelines, and application in non-sour environments
Scope and Purpose
API TR 2572-2013, officially titled API Technical Report: Carbon Steel, Casing and Tubing, for Non-Corrosive Service, provides engineering guidance for the selection, manufacture, and qualification of carbon steel casing and tubing intended for environments where hydrogen sulfide (H₂S) is not present, i.e., non-sour or non-corrosive service. This technical report supplements the requirements of API Specification 5CT (Specification for Casing and Tubing) by offering alternative, less stringent provisions that are appropriate when the risk of sulfide stress cracking (SSC) or other corrosion mechanisms is negligible.
The document is not a standard or specification but rather a technical report that consolidates recommended practices developed by industry experts. It is intended for use by well designers, drilling engineers, procurement specialists, and manufacturers who wish to optimize material costs and reduce unnecessary testing requirements for wells that operate in benign environments. By referencing API TR 2572, operators can maintain safety while achieving economic efficiency.
Tip: API TR 2572 is often used in conjunction with API 5CT. Always verify with your regulatory body that the relaxed requirements are acceptable for the specific field application.
Technical Requirements and Material Specifications
API TR 2572 defines the mechanical and chemical property requirements for commonly used carbon steel grades. The report permits deviations from some API 5CT requirements, particularly regarding heat treatment verification, non-destructive examination (NDE) coverage, and the frequency of tensile and hardness tests.
Grade Designations and Mechanical Properties
The following table summarizes the minimum yield strength and tensile strength requirements for the grades most frequently specified under API TR 2572 for non-corrosive service. All values are based on the API 5CT baseline but incorporate the relaxed acceptance criteria allowed by the technical report.
| Grade | Minimum Yield Strength (ksi) | Minimum Tensile Strength (ksi) | Maximum Hardness (HRC) | Typical Application |
|---|---|---|---|---|
| H40 | 40 | 60 | — | Shallow wells, low-pressure service |
| J55 | 55 | 75 | — | Medium-depth casing, conventional production |
| K55 | 55 | 95 | — | Collapse-resistant applications |
| N80 | 80 | 100 | 24 | Intermediate depth, moderate pressure |
| L80 | 80 | 95 | 23 | Deep wells, low H₂S risk environments |
| P110 | 110 | 125 | 30 | High-pressure, high-temperature (HPHT) non-sour wells |
Key advantage: For non-corrosive service, the technical report often permits reduced frequency of Charpy impact testing and lower NDE acceptance standards, which can significantly lower manufacturing costs without compromising short-term integrity.
Implementation and Manufacturing Considerations
Adoption of API TR 2572 requires close coordination between the purchaser and the manufacturer. The technical report outlines several options that may be selected to tailor the product to the well’s specific conditions. Important implementation aspects include:
- Material selection: The purchaser must define the maximum allowable hardness and the required toughness level. For non-corrosive service, the risk of hydrogen embrittlement is absent, so higher hardness grades like P110 can be used without the stringent hardness restrictions applied in sour service.
- Heat treatment: API TR 2572 allows alternatives to full quenching and tempering for certain grades, such as normalizing or stress relieving, provided that the mechanical properties remain within the specified ranges.
- Inspection and testing: The technical report defines reduced sampling plans for tensile and hardness tests compared to API 5CT. For example, one heat per 200 pipes may be tested rather than one per 100. Non-destructive inspection may be limited to only the pipe body, with threaded ends inspected visually.
- Traceability: While full material traceability is recommended, the report permits alternative marking methods (e.g., die stamping instead of continuous laser marking) when the service environment is non-corrosive.
Consideration: The use of API TR 2572 does not eliminate the need for proper well design. Engineers should verify that the reduced testing plan does not mask quality issues that could lead to premature failure under dynamic loading or thermal cycling.
Compliance and Certification Notes
API TR 2572 is not a mandatory standard; compliance is voluntary unless specifically invoked in a purchase contract or regulatory framework. However, because it references API 5CT and other API documents, products manufactured under the technical report can be certified to API 5CT requirements with the notation “Manufactured per API TR 2572 for non-corrosive service.” This distinction is important for end users who require traceable documentation.
Regulatory acceptance varies by jurisdiction. Some national oil companies and regulatory bodies may require full API 5CT certification for all well equipment, regardless of service condition. Others allow the relaxed provisions of API TR 2572 once a non-corrosive environment has been confirmed by fluid analysis and well history.
Critical: API TR 2572 is intended exclusively for non-corrosive (non-sour) service. Using its relaxed requirements in any environment where H₂S is present or where the pH is below 5.5 can result in catastrophic sulfide stress cracking. Always perform a thorough corrosion risk assessment before selecting this technical report.
For manufacturers, maintaining API 5CT monogram rights while also offering products under API TR 2572 requires clear segregation of quality records. The manufacturer should produce a detailed compliance matrix that maps each requirement of the technical report to the corresponding API 5CT clause, showing where deviations are taken.
The report was reaffirmed in 2018 and remains valid. Users should check for any updates or amendments from API, particularly regarding the addition of higher-strength grades (e.g., Q125) for non-corrosive applications.
Frequently Asked Questions
Q: How does API TR 2572 differ from API 5CT?
A: API 5CT is a full specification covering all service conditions, including sour service (with added requirements for hardness control, testing, and traceability). API TR 2572 is a technical report that permits relaxed testing and inspection for carbon steel casing and tubing used exclusively in non-corrosive, non-sour environments. It does not supersede API 5CT but rather supplements it with alternative provisions.
A: API 5CT is a full specification covering all service conditions, including sour service (with added requirements for hardness control, testing, and traceability). API TR 2572 is a technical report that permits relaxed testing and inspection for carbon steel casing and tubing used exclusively in non-corrosive, non-sour environments. It does not supersede API 5CT but rather supplements it with alternative provisions.
Q: Can I use API TR 2572 for tubing in a well that occasionally produces small amounts of H₂S?
A: No. API TR 2572 is strictly for non-corrosive service, meaning no H₂S and no corrosive fluids (e.g., pH ≥ 5.5, no free water containing CO₂ or H₂S). Any H₂S exposure, even intermittent, requires compliance with full API 5CT sour-service grades or other suitable standards (e.g., NACE MR0175).
A: No. API TR 2572 is strictly for non-corrosive service, meaning no H₂S and no corrosive fluids (e.g., pH ≥ 5.5, no free water containing CO₂ or H₂S). Any H₂S exposure, even intermittent, requires compliance with full API 5CT sour-service grades or other suitable standards (e.g., NACE MR0175).
Q: Is API TR 2572 internationally recognized?
A: Yes. While developed by the American Petroleum Institute, the report is widely referenced in the Middle East, Africa, South America, and Asia. Many international operators include it in their procurement documents when the field conditions have been confirmed as non-corrosive. However, check local regulations as some countries mandate strict adherence to API 5CT without deviation.
A: Yes. While developed by the American Petroleum Institute, the report is widely referenced in the Middle East, Africa, South America, and Asia. Many international operators include it in their procurement documents when the field conditions have been confirmed as non-corrosive. However, check local regulations as some countries mandate strict adherence to API 5CT without deviation.