C90 Casing Pipe: High-Performance OCTG for Sour-Service Wells
What Is API 5CT C90 Casing?
C90 is a high-strength, sour-service casing grade defined under API 5CT, with a controlled yield strength of 90,000–105,000 psi and a minimum tensile strength of 100,000 psi. ing>C90 casingAPI 5CT C90 casing undergoes quenching and tempering to achieve a refined microstructure that balances high strength with superior toughness in corrosive downhole environments. C90 casing tubing covers sizes from 2⅜″ to 13⅜″, serving both production and intermediate string apptlicaions in medium-to-deep sour gas and sour oil wells. As a reliable C90 steel pipe, it offers an optimal combination of mechanical performance and H₂S resistance, making it the preferred choice where API 5CT C90 casing tubing is required for safe, long-term well integrity in aggressive sour-service conditions.
- Material Grade: C90-1, C90-2
- Applicable Product: Casing & Tubing 2⅜″–13⅜″
- Thread Types: BC, STC / LTC, Premium Connections
- Available Lengths: R1 / R2 / R3
- Service Environment: Sour Service (H₂S), NACE MR0175 Compliant
Note: For C90-1, the lower limit of Mo may not be set when the wall thickness is less than 17.78 mm; N.L. in the standard table means no limit.
| Grade | Yield strength Rp0.2 / MPa | Tensile strength Rm / MPa | Hardness max | Elongation |
| C90-1 | 621–724 | ≥689 | HRC 25.4 / HBW 255 | 0.5% |
| C90-2 | 621–724 | ≥689 | HRC 25.4 / HBW 255 | 0.5% |
Test requirements for C90 Casing
| Steel Grade | Mandatory Tests | Supplementary Tests | NDT | Corrosion Test | Key Control Requirements |
| C90 Type 1 C90 Type 2 | Chemical analysis Tensile,Hardness Hydrostatic pressure | SSC,Impact | UT+MT | NACE TM0177 | Anti-SSC |
API 5CT Sour Service Grade
C90 Casing Tubing Dimensions & Specifications
Standard API 5CT C90 casing and tubing performance properties covering common OD sizes from 4-1/2″ to 13-3/8″. All values per API 5CT / ISO 11960. Collapse and internal yield pressure ratings based on minimum yield strength of 90,000 psi.
| OD (in.) | Wall Thickness (in.) | Weight (lb/ft) | Drift Diameter (in.) | Collapse Resistance (psi) | Internal Yield Pressure (psi) | Grade |
|---|---|---|---|---|---|---|
| 4-1/2″ | 0.205 | 9.50 | 4.003 | 5,410 | 7,180 | C90 |
| 4-1/2″ | 0.224 | 10.50 | 3.965 | 6,600 | 7,840 | C90 |
| 4-1/2″ | 0.250 | 11.60 | 3.913 | 8,220 | 8,750 | C90 |
| 4-1/2″ | 0.290 | 13.50 | 3.833 | 10,780 | 10,150 | C90 |
| 5-1/2″ | 0.244 | 14.00 | 4.925 | 5,000 | 6,990 | C90 |
| 5-1/2″ | 0.275 | 15.50 | 4.863 | 6,470 | 7,880 | C90 |
| 5-1/2″ | 0.304 | 17.00 | 4.805 | 7,740 | 8,710 | C90 |
| 5-1/2″ | 0.361 | 20.00 | 4.691 | 10,350 | 10,340 | C90 |
| 5-1/2″ | 0.415 | 23.00 | 4.583 | 13,030 | 11,890 | C90 |
| 7″ | 0.272 | 20.00 | 6.369 | 3,830 | 6,120 | C90 |
| 7″ | 0.317 | 23.00 | 6.279 | 5,220 | 7,130 | C90 |
| 7″ | 0.362 | 26.00 | 6.189 | 6,770 | 8,150 | C90 |
| 7″ | 0.408 | 29.00 | 6.097 | 8,170 | 9,180 | C90 |
| 7″ | 0.453 | 32.00 | 6.007 | 9,640 | 10,190 | C90 |
| 7″ | 0.498 | 35.00 | 5.917 | 11,240 | 11,210 | C90 |
| 7″ | 0.540 | 38.00 | 5.833 | 12,760 | 12,150 | C90 |
| 9-5/8″ | 0.352 | 36.00 | 8.835 | 3,090 | 5,760 | C90 |
| 9-5/8″ | 0.395 | 40.00 | 8.749 | 4,050 | 6,470 | C90 |
| 9-5/8″ | 0.435 | 43.50 | 8.669 | 5,000 | 7,120 | C90 |
| 9-5/8″ | 0.472 | 47.00 | 8.595 | 5,860 | 7,720 | C90 |
| 9-5/8″ | 0.545 | 53.50 | 8.449 | 7,720 | 8,920 | C90 |
| 13-3/8″ | 0.330 | 48.00 | 12.615 | 1,490 | 3,890 | C90 |
| 13-3/8″ | 0.380 | 54.50 | 12.515 | 2,060 | 4,480 | C90 |
| 13-3/8″ | 0.430 | 61.00 | 12.415 | 2,670 | 5,070 | C90 |
| 13-3/8″ | 0.480 | 68.00 | 12.315 | 3,290 | 5,650 | C90 |
| 13-3/8″ | 0.514 | 72.00 | 12.247 | 3,680 | 6,050 | C90 |
* Performance values are calculated per API 5CT / ISO 11960 formulas based on minimum yield strength of 90,000 psi. Actual ratings may vary by manufacturer. Please confirm exact specifications with our technical team before ordering.
Where C90 Is Used
Applications of C90 Casing in Oil & Gas
API 5CT C90 casing tubing is purpose-built for the most demanding downhole environments where standard grades cannot ensure long-term well integrity.
SOUR SERVICE
Sour Gas Wells (H₂S Environments)
C90 resists sulfide stress cracking in hydrogen sulfide wells. NACE MR0175-compliant, it keeps casing integrity where standard grades fail under H₂S exposure.
NACE MR0175
SSC Resistant
ISO 15156
HIGH PRESSURE
Deep & High-Pressure Formations
With 90,000 psi min yield and tight strength tolerance, API 5CT C90 casing tubing handles extreme collapse and burst loads in wells exceeding 15,000 ft depth.
90–105 ksi YS
Q&T Process
15,000+ ft
OFFSHORE
Offshore & Subsea Drilling
Offshore wells demand zero-failure casing. C90’s controlled hardness and impact toughness make API 5CT C90 casing tubing ideal for subsea completions in corrosive marine conditions.
HRC ≤ 25.4
Charpy Tested
Premium Conn.
Grade Comparison
Why Choose C90 Over L80 or T95?
Selecting the right OCTG grade depends on well chemistry, depth, and budget. Here’s how API 5CT C90 casing tubing compares to L80 and T95 in the properties that matter most.
C90 vs L80
SSC ADVANTAGE
Superior Sour-Service Performance
L80 is widely used for mild sour wells, but its SSC resistance is limited. C90 offers a significant upgrade in H₂S environments without a dramatic cost increase.
- Full NACE MR0175 / ISO 15156 compliance
- Mandatory hardness cap (HRC ≤ 25.4) vs L80’s HRC ≤ 23
- 10,000 psi higher yield strength than L80
- Quench-and-temper only — tighter microstructure control
- Handles deeper sour wells L80 cannot safely reach
C90 vs T95
COST ADVANTAGE
Better Value for Most Sour Wells
T95 offers slightly higher yield strength (95 ksi min), but at a steeper price. For the majority of sour-service applications, C90 delivers the same H₂S protection at lower cost.
- Same NACE / ISO sour-service qualification as T95
- 10–15% lower per-ton cost than T95 on average
- Wider availability and shorter mill lead times
- Sufficient collapse resistance for most well designs
- Preferred by operators when T95’s extra 5 ksi isn’t needed
| Property | L80 | C90 (Recommended) | T95 |
|---|---|---|---|
| Yield Strength (ksi) | 80 – 95 | 90 – 105 | 95 – 110 |
| Min Tensile Strength (ksi) | 95 | 100 | 105 |
| Sour Service (H₂S) | Limited | Full Compliance | Full Compliance |
| NACE MR0175 / ISO 15156 | Conditional | Yes | Yes |
| Max Hardness (HRC) | ≤ 23.0 | ≤ 25.4 | ≤ 25.4 |
| Heat Treatment | Q&T or Normalize | Q&T Only | Q&T Only |
| SSC Resistance | Moderate | High | High |
| Relative Cost | $ | $$ | $$$ |
| Mill Availability | Wide | Good | Limited |
| Best For | Sweet / mild sour wells | Sour wells, deep HPHT | Extreme sour / ultra-deep |
Bottom line: API 5CT C90 casing tubing sits in the sweet spot — strong enough for most sour and high-pressure wells, compliant with the same NACE standards as T95, yet more cost-effective and readily available than T95. Choose L80 only for sweet wells; upgrade to T95 only when your well design demands yield strength above 90 ksi.
Designed for sour-service oil & gas wells containing H₂S. Meets API 5CT SSC-resistance requirements.
Available in OD from 4-1/2″ to 20″. Reference the dimensions table above for wall thickness and weight.
C90 offers superior SSC resistance with higher yield strength (62.1–72.5 ksi vs 80 ksi max for L80) and mandatory hardness limits.
Yes. C90 is a grade defined within API Specification 5CT for casing and tubing used in wells.
