TP80SS Casing With Premium Connection: Proprietary Severe Sour Service OCTG Manufactured in Accordance with API 5CT
TP80SS casing is TPCO proprietary quenched and tempered high-performance sour service steel grade developed for oil and gas wells under harsh hydrogen sulfide (H₂S) corrosion environments. Equipped with premium gas-tight connections, TP80SS casing delivers balanced high strength, controlled hardness, excellent sulfide stress cracking (SSC) resistance and reliable sealing performance, widely applied in medium-deep sour gas wells with low carbon dioxide partial pressure.
Core Definition of TP80SS Casing
Grade Code Meaning
- TP: Abbreviation of TPCO (Tianjin Pipe Corporation), independent proprietary OCTG steel grade series
- 80: Specified minimum yield strength reaches 80 ksi (552 MPa), similar to API L80 strength level.
- SS: Sour Service, dedicated for wells containing corrosive H₂S medium
Mandatory Mechanical Property Parameters (Compliant with Latest API 5CT 10th Edition)
| Performance Index | TP80SS Standard Requirement |
|---|---|
| Yield Strength Range | 80 ksi – 95 ksi (552 MPa ~ 655 MPa) |
| Minimum Tensile Strength | 95 ksi (655 MPa) |
| Maximum Hardness | 23 HRC (strict hardness control to prevent SSC failure) |
| NACE SSC Test Requirement | NACE TM 0177 Method A, loaded at 90% SMYS (Specified Minimum Yield Strength) |
| Heat Treatment Process | Full-length quenched & tempered (Q&T), full-body uniform heat treatment mandatory |
Different from conventional API L80-1 carbon steel casing, TP80SS is qualified under a more stringent SSC test load (90% SMYS), whereas TP110SS is evaluated at 85% SMYS due to its higher strength level.
Application Scope & Corrosion Well Material Selection Basis for TP80SS Casing
According to TPCO official corrosive well material selection flowchart, TP80SS belongs to low-alloy severe sour service steel, with clear applicable medium threshold:
Applicable Medium Condition
Judgment standard for selecting TP80SS:
- CO₂ partial pressure (PCO₂) ≤ 0.02 MPa (low carbon dioxide environment)
- H₂S partial pressure (PH₂S) ≥ 0.0003 MPa (effective sulfide corrosion exists in formation fluid)
Under above working conditions, TP80SS, C90, T95, C110, TP90SS, TP95SS, TP110SS are preferred low-alloy anti-sulfide casing alternatives. If PCO₂ exceeds 0.02 MPa with high CO₂ corrosion, stainless steel series (13Cr, SUP13Cr, 22Cr) or CRA nickel-based alloys shall replace TP80SS.
Typical Well Site Scenarios
- Onshore medium-deep sour crude oil wells and sour gas wells
- Medium-pressure strata with low CO₂ and stable H₂S content
- Wells requiring medium yield strength and long-term anti-sulfide service life
- Projects seeking a lower-cost alternative to corrosion-resistant alloys (CRAs)
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Advantages of TP80SS Casing Matched with Premium Connection
Standard BTC, STC, LTC API round/buttress threads have hidden leakage risks under long-term sour medium and alternating downhole pressure. TP80SS equipped with premium connection solves sealing and structural defects of conventional threads:
Core Premium Connection Performance Benefits
- Gas-tight sealing capability: Multi-stage metal-to-metal sealing structure, zero gas leakage under high-pressure sour fluid, suitable for sour gas production wells
- Higher torque resistance: Optimized tooth profile design, avoids thread gluing and deformation during running casing under high torque load
- Special clearance anti-jamming structure: Smooth make-up & breakout, reduces construction failure rate in complex deviated wells and horizontal wells
- Corrosion protection for thread contact surface: Special thread anti-corrosion coating matched with TP80SS anti-sulfide substrate, prevents thread crevice corrosion caused by H₂S
Compatible Premium Connection Types of TPCO TP80SS Casing
- HYD series gas-tight premium threads
- Customized metal-sealed premium couplings for sour service
- Special clearance premium connections with black identification band
Production & Inspection Standards of TP80SS Casing with Premium Connection
Manufacturing Restrictions
TP80SS is produced as seamless casing only; ERW welded process is not allowed for this sour service grade. Full-length full-body non-destructive testing (NDT) is mandatory.
Complete Inspection Items for Delivery
- Visual surface inspection, dimensional tolerance measurement (outer diameter, wall thickness, length R1/R2/R3)
- Chemical composition spectroscopic analysis, full mechanical tensile/hardness/Charpy impact test
- NACE TM 0177 SSC corrosion test report
- Full-length ultrasonic/flux leakage NDT scanning
- Premium thread gauge inspection, coupling assembly fit test, hydrostatic pressure tightness test
Comparison: TP80SS vs API L80-1 Casing
| Comparison Item | TP80SS Casing | API 5CT L80-1 Casing |
|---|---|---|
| NACE SSC Test Load | 90% SMYS, strict anti-sulfide threshold | No mandatory unified 90% SMYS sour test standard |
| Applicable H₂S Environment | Formal severe sour service proprietary grade | Mild occasional sour wells only |
| Heat Treatment Control | Custom Q&T formula optimized for SSC resistance | Basic standard quenched & tempered process |
| Premium Connection Matching | Matched dedicated anti-sulfide metal sealing threads | Conventional API threads as mainstream match |
test and inspection of casing pipe
Casing pipe certificate
FAQ
Q1: What does TP80SS stand for?
A1: TP refers to TPCO proprietary steel grade, 80 means minimum yield strength 80 ksi, SS is the abbreviation of Sour Service, designed specially for H₂S-containing corrosive oil and gas wells.
Q2: What working conditions are not suitable for TP80SS casing?
A2: TP80SS is not recommended when CO₂ partial pressure exceeds 0.02 MPa. High CO₂ medium will cause severe uniform carbonic acid corrosion on low-alloy steel; users shall select 13Cr, SUP13Cr duplex stainless steel or CRA nickel-based alloys instead.
Q3: Is TP80SS available as ERW welded casing?
A3: No. TP80SS is supplied as seamless casing only. Although API 5CT permits ERW manufacturing for certain standard grades, ERW is not used for TP80SS proprietary sour service casing.
Q4: Why is premium connection necessary for TP80SS sour service casing?
A4: Conventional API threads have gaps between tooth surfaces. H₂S medium penetrates gaps and triggers thread crevice corrosion and stress cracking. Premium connection adopts metal-to-metal full sealing structure to isolate corrosive fluid, ensuring long-term sealing integrity in sour wells.
Q5: What is the maximum hardness limit of TP80SS casing and why?
A5: The maximum hardness of TP80SS is controlled at 23 HRC according to TPCO specification. Higher hardness will significantly reduce the steel's resistance to sulfide stress cracking, leading to sudden pipe failure under H₂S environment.
Q6: What NACE test standard does TP80SS comply with?
A6: TP80SS follows NACE TM 0177 Method A standard, tested under 90% specified minimum yield strength (SMYS), with stricter evaluation criteria than high-strength TP110SS (85% SMYS test load).
Q7: Can TP80SS casing be used in wells with both H₂S and high temperature?
A7: TP80SS fits medium-temperature sour wells under low CO₂ condition. For high-temperature wells with both high CO₂ and H₂S, users need to upgrade to SUP13Cr, 22Cr or nickel-based CRA alloys for higher temperature and corrosion resistance.
Q8: What PSL levels can TP80SS premium connection casing provide?
A8: TPCO supplies TP80SS casing in PSL1, PSL2 and PSL3 grades. PSL2 and PSL3 add extra strict inspection rules including extended impact testing and tighter NDT acceptance limits in accordance with API 5CT 10th Edition Annex H.
Conclusion
TP80SS casing with premium connection is a mature proprietary OCTG solution developed by TPCO targeting severe low-CO₂ sour service wells. It balances medium high mechanical strength, strict anti-SSC performance under NACE TM 0177 90% SMYS test, and full gas-tight reliability from premium metal sealing couplings. Compared with standard API L80-1 casing, it delivers stable safety margin for long-term sour gas and crude oil exploitation. When project medium meets PCO₂ ≤0.02 MPa and PH₂S ≥0.0003 MPa, TP80SS with premium connection becomes a cost-effective alternative to expensive stainless steel and nickel-based corrosion resistant alloys for oil and gas operators worldwide.