What is API 5CT J55 Oilfield Casing Pipe?
API 5CT J55 is an entry-level steel grade defined by the American Petroleum Institute (API) for oil and gas well operations.
Purpose: It is used as a structural retainer for the walls of oil and gas wells to ensure the drilling process proceeds smoothly and the well remains stable after completion.
Application: Primarily used in shallow wells, medium-shallow wells, or low-pressure environments.
Status: It is one of the most economical and widely used steel grades due to its lower yield strength compared to higher grades like N80 or P110.
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API 5CT J55 Color Code
API 5CT specifies color bands to ensure quick visual identification on the rig site.
| Steel Grade | Pipe Body Color Band | Coupling Color |
| J55 | One Green Band | Entire Coupling Green |
API 5CT J55 Specification Table
| Item | Details |
| Standard | API Spec 5CT / ISO 11960 |
| Steel Grade | J55 |
| Outer Diameter (OD) | 4-1/2" – 20" (114.3mm – 508mm) |
| Wall Thickness (WT) | 5.21mm – 22.22mm (Depends on OD) |
| Length Range | R1 (4.88–7.62m), R2 (7.62–10.36m), R3 (>10.36m) |
| Product Specification Level | PSL1, PSL2, PSL3 |
Chemical Composition and Mechanical Properties
Chemical Composition (%)
| Grade | C | Mn | P (max) | S (max) | Si |
| J55 | Not Specified | Not Specified | 0.030 | 0.030 | Not Specified |
Mechanical Properties
| Grade | Yield Strength (MPa / ksi) | Tensile Strength (min) | Elongation | Hardness |
| J55 | 379–552 MPa (55–80 ksi) | ≥ 517 MPa (75 ksi) | Per API Formula | Not Required |
API 5CT J55 Casing Pipe Dimensions Table
| Outer Diameter (OD) | Nominal Weight | Wall Thickness (WT) | Inner Diameter (ID) | Drift Diameter |
| inch (mm) | lb/ft ( kg/m ) | inch (mm) | inch (mm) | inch (mm) |
| 4-1/2" (114.30) | 9.50 (14.14) | 0.205 (5.21) | 4.090 (103.89) | 3.965 (100.71) |
| 10.50 (15.63) | 0.224 (5.69) | 4.052 (102.92) | 3.927 (99.75) | |
| 11.60 (17.26) | 0.250 (6.35) | 4.000 (101.60) | 3.875 (98.43) | |
| 5" (127.00) | 11.50 (17.11) | 0.220 (5.59) | 4.560 (115.82) | 4.435 (112.65) |
| 13.00 (19.35) | 0.253 (6.43) | 4.494 (114.15) | 4.369 (110.97) | |
| 5-1/2" (139.70) | 14.00 (20.83) | 0.244 (6.20) | 5.012 (127.30) | 4.887 (124.13) |
| 15.50 (23.07) | 0.275 (6.98) | 4.950 (125.73) | 4.825 (122.56) | |
| 17.00 (25.30) | 0.304 (7.72) | 4.892 (124.26) | 4.767 (121.08) | |
| 6-5/8" (168.28) | 20.00 (29.76) | 0.288 (7.32) | 6.049 (153.64) | 5.924 (150.47) |
| 24.00 (35.72) | 0.352 (8.94) | 5.921 (150.39) | 5.796 (147.22) | |
| 7" (177.80) | 17.00 (25.30) | 0.231 (5.87) | 6.538 (166.07) | 6.413 (162.89) |
| 20.00 (29.76) | 0.272 (6.91) | 6.456 (163.98) | 6.331 (160.81) | |
| 23.00 (34.23) | 0.317 (8.05) | 6.366 (161.70) | 6.241 (158.52) | |
| 7-5/8" (193.68) | 24.00 (35.72) | 0.300 (7.62) | 7.025 (178.44) | 6.900 (175.26) |
| 26.40 (39.29) | 0.328 (8.33) | 6.969 (177.01) | 6.844 (173.84) | |
| 8-5/8" (219.08) | 24.00 (35.72) | 0.264 (6.71) | 8.097 (205.66) | 7.972 (202.49) |
| 32.00 (47.62) | 0.352 (8.94) | 7.921 (201.19) | 7.796 (198.02) | |
| 9-5/8" (244.48) | 36.00 (53.57) | 0.352 (8.94) | 8.921 (226.59) | 8.765 (222.63) |
| 40.00 (59.53) | 0.395 (10.03) | 8.835 (224.41) | 8.679 (220.45) | |
| 10-3/4" (273.05) | 32.75 (48.74) | 0.279 (7.09) | 10.192 (258.88) | 10.036 (254.91) |
| 40.50 (60.27) | 0.350 (8.89) | 10.050 (255.27) | 9.894 (251.31) | |
| 13-3/8" (339.72) | 48.00 (71.43) | 0.330 (8.38) | 12.715 (322.96) | 12.559 (319.00) |
| 54.50 (81.10) | 0.380 (9.65) | 12.615 (320.42) | 12.459 (316.46) | |
| 16" (406.40) | 65.00 (96.73) | 0.375 (9.53) | 15.250 (387.35) | 15.062 (382.57) |
| 18-5/8" (473.08) | 87.50 (130.21) | 0.435 (11.05) | 17.755 (450.98) | 17.567 (446.20) |
| 20" (508.00) | 94.00 (139.89) | 0.438 (11.13) | 19.124 (485.75) | 18.936 (480.97) |
Tolerances Table
| Parameter | Tolerance |
| Outer Diameter (OD) | < 4-1/2": ±0.79mm; ≥ 4-1/2": -0.75%D, +1.00%D |
| Wall Thickness (WT) | -12.5% (Minimum API requirement) |
| Weight | Single joint: -3.5% to +6.5%; Carload: -1.75% |
| Straightness | Total deviation ≤ 0.2% of the total length |
Features of API 5CT J55 Casing Tube
High Cost-Efficiency: The most affordable grade for non-critical well sections.
Good Weldability: Lower alloy content makes it easier to weld if necessary.
Versatility: Suitable for surface casing, intermediate casing, and production casing in low-pressure wells.
Standard Corrosion Resistance: Suitable for general environments, but not recommended for high H2S (sour gas) or high CO2 environments.
Easy Threading: Its mechanical properties allow for easy machining of STC, LTC, and BTC threads.
Test and Inspection of API 5CT J55 Pipes
| Test Item | Description |
| Hydrostatic Test | Every pipe must be pressure tested to ensure no leakage. |
| NDT (Non-Destructive) | Includes Ultrasonic (UT), Magnetic Particle (MPI), or Eddy Current testing. |
| Tensile Test | Verifies yield strength, tensile strength, and elongation. |
| Flattening Test | Specifically for ERW pipes to ensure weld seam integrity. |
| Visual/Dimension | Checking threads, OD, wall thickness, and surface defects. |
| Drift Test | Ensuring a standard mandrel can pass through the pipe. |
API 5CT J55 Casing pipe factory
API 5CT J55 oil country tubular goods Certificate
FAQ
What is the difference between J55 and L80 corrosion?
The main difference between J55 and L80 regarding corrosion is their resistance to Sour Service
| Feature | J55 | L80 |
| Corrosion Environment | Sweet Service (General) | Sour Service ( H2S Presence) |
| Cracking Resistance | Low | High (Resists SSC) |
| Max Hardness Limit | None | Max 23 HRC |
| Material Cost | Economical / Cheap | Expensive |
What is the difference between J55 and K55 casing?
| Feature | API 5CT J55 | API 5CT K55 | Key Difference |
| Yield Strength | 55,000 - 80,000 psi (379 - 552 MPa) | 55,000 - 80,000 psi (379 - 552 MPa) | Identical |
| Tensile Strength | Min 75,000 psi (517 MPa) | Min 95,000 psi (655 MPa) | K55 is ~26% stronger in tension |
| Elongation | Per API 5CT formula | Per API 5CT formula | Similar requirements |
| Tensile Load Capacity | Standard | Higher | K55 supports heavier string weight |
| Impact Requirements | No mandatory test (PSL1) | No mandatory test (PSL1) | Both are basic carbon steel grades |
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