What Is API L80 Casing
API L80 is a high-strength casing grade defined under API SPEC 5CT for oil and gas drilling and production. The L series is designed for service in corrosive environments, including wells containing carbon dioxide and hydrogen sulfide, where strength alone is insufficient and controlled hardness and toughness are required. L80 casing is supplied with either a 1 or 1Cr designation depending on the heat treatment route, and both provide a minimum yield strength of 80 ksi with a controlled maximum to limit susceptibility to sulfide stress cracking.
Key Technical Parameters
| Parameter | Value |
|---|---|
| Material grade | L80 (carbon steel with chromium alloying) |
| Yield strength | 552 to 655 MPa (80 to 95 ksi) |
| Tensile strength | 655 MPa minimum (95 ksi) |
| Chemical composition | C 0.25-0.30 percent, Cr 0.90-1.10 percent, Mn 0.6-0.8 percent |
| Outside diameter | 114.3 to 508 mm (4.5 to 20 in) |
| Wall thickness | 6.35 to 25.4 mm (0.25 to 1 in) |
| Length ranges | R-1: 4.88-7.62 m, R-2: 7.62-10.36 m, R-3: over 10.36 m |
| Thread types | BTC (short round thread), LTC (long round thread) |
| Standards | API SPEC 5CT |
Applications
Oil and gas wells: casing in high-corrosion environments with CO2 or H2S to maintain wellbore integrity. Geothermal wells: suitable for high-temperature and corrosive conditions. Marine engineering: resists seawater corrosion in offshore platform applications.
Advantages
Corrosion resistance: the chromium content of 0.9 to 1.1 percent forms a protective oxide layer that reduces corrosion rates. High strength: tensile strength of at least 655 MPa supports deep-well service. Cost effectiveness: lower lifecycle cost than stainless steel alternatives in moderate sour service. Standardization: full compliance with API 5CT ensures global compatibility of threads and inspection requirements.
Grade Comparison
| Grade | Yield strength (ksi) | Key feature |
|---|---|---|
| J55 | 55 | Basic carbon steel |
| N80 | 80 | High strength, no corrosion resistance |
| L80 | 80 | Corrosion-resistant, controlled hardness |
Testing and Inspection
L80 casing is manufactured and tested per API SPEC 5CT, including chemical analysis, tensile testing, hardness testing, flattening and bending where applicable, hydrostatic pressure testing, and non-destructive examination. For sour service, additional requirements such as hardness limits and sulfide stress cracking testing apply.
Frequently Asked Questions
Q: What does L80 mean in API 5CT?
A: L indicates a restricted-yield grade designed for sour service, and 80 refers to the minimum yield strength of 80 ksi (552 MPa).
Q: What is the difference between L80 and N80 casing?
A: N80 has similar strength but no corrosion resistance requirement; L80 has controlled hardness and chromium addition for service in CO2 and H2S environments.
Q: Can L80 casing be used in sour wells?
A: Yes. L80 is a standard sour-service grade, provided the applicable hardness limits and testing per API 5CT and industry practice are met.
Q: What threads are available on L80 casing?
A: Short round thread (BTC) and long round thread (LTC) are common, with premium connections available for critical wells.
Q: What sizes is L80 casing available in?
A: Outside diameters typically range from 114.3 to 508 mm with wall thicknesses from 6.35 to 25.4 mm, in R-1, R-2, or R-3 length ranges.
Q: What is the maximum hardness of L80?
A> Per API 5CT, L80 has a maximum hardness requirement of 23 HRC, which is verified by hardness testing on each heat-treated lot.
For L80 casing quotations with size, thread, and testing requirements, contact our sales team.
