J55 is a casing steel grade defined by the API (American Petroleum Institute) standard for oil drilling. It belongs to the category of high-quality carbon structural steel, and its domestic equivalent is the DZ series. This casing is mainly used to support the wellbore, isolate formation pressure, and transport oil and gas, and is widely used in oil wells, gas wells, geothermal wells, and other applications. Its outer diameter ranges from 139.7 to 244.5 mm, wall thickness from 7.72 to 11.05 mm, and lengths are divided into three categories: R-1 (4.88-7.62 meters), R-2 (7.62-10.36 meters), and R-3 (over 10.36 meters).
J55 casing is classified into short round thread and long round thread types. Both the inner and outer surfaces must be free of folds and cracks, and the couplings must be smooth and burr-free. The production process adopts hot rolling or cold drawing processes and must comply with the national industry standard SY/T6194-96 and the international specification API SPEC 5CT. The chemical composition requires that the sulfur and phosphorus contents be less than 0.045%, and the physical properties must be tested by flattening, tensile and hydrostatic tests.
API 5CT J55 pipe Chemical Composition
|
Grade |
C |
Si |
Mn |
P |
S |
Cr |
Ni |
Cu |
Mo |
|
API 5CT J55 |
0.34-0.39 |
0.20-0.35 |
1.25-1.50 |
0.020 |
0.015 |
0.15 |
0.20 |
0.20 |
/ |
API 5CT J55 OCTG Casing Mechanical Property
|
Steel Grade |
Yield Strength (Mpa) |
Tensile Strength (Mpa) |
Total Elongation Under Load % |
|
API 5CT J55 |
379-552 |
≥517 |
0.5 |
API 5CT J55 Casing and tubing Tolerance
|
Item |
Allowable tolerance |
|
|
Outer diameter |
Pipe body |
D≤101.60mm±0.79mm |
|
D≥114.30mm+1.0% |
||
|
-0.5% |
||
|
Wall thickness |
-12.5% |
|
|
Wight |
Single piece |
+6.5%+3.5% |
|
Total weight |
-1.75 |
|
API 5CT J55 OCTG Size Chart
|
Outer Diameter |
Wall Thickness |
Weight |
Grade |
Threaded |
Length |
|
|
in |
mm |
kg/m |
lb/ft |
|||
|
4 1/2″ |
114.3 |
14.14-22.47 |
9.50-11.50 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
5″ |
127 |
17.11-35.86 |
11.50-24.10 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
5 1/2″ |
139.7 |
20.83-34.23 |
14.00-23.00 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
6 5/8″ |
168.28 |
29.76-35.72 |
20.00-24.00 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
7″ |
177.8 |
25.30-56.55 |
17.00-38.00 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
7 5/8″ |
193.68 |
35.72-63.69 |
24.00-42.80 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
8 5/8″ |
219.08 |
35.72-72.92 |
24.00-49.00 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
9 5/8″ |
244.48 |
48.07-86.91 |
32.30-58.40 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
10 3/4″ |
273.05 |
48.73-97.77 |
32.75-65.70 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
11 3/4″ |
298.45 |
62.50-89.29 |
42.00-60.00 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
|
13 3/8″ |
339.72 |
71.43-107.15 |
48.00-72.00 |
J55 |
LTC/STC/BTC |
R1/R2/R3 |
API 5CT Grade J55 Casing Pipe
Applications
API 5CT J55 seamless casing is a widely used casing type in the oil and gas industry. Its core applications include:
Shallow and Medium-Deep Well Support
Suitable for shallow oil and gas wells with moderate formation pressure. Through cementing processes, it forms a stable wellbore structure, preventing collapse.
Non-Corrosive Environments
In formations without corrosive gases such as hydrogen sulfide (H₂S) or carbon dioxide (CO₂), J55 casing is the preferred choice due to its cost advantage.
Comparison: In acidic environments (such as those containing H₂S), it is necessary to upgrade to corrosion-resistant steel grades such as L80 or C90.
Water Wells and Geological Exploration
Used in water well drilling to support the wellbore and isolate different aquifers; in geological exploration, it serves as temporary casing to protect drilling equipment.
Low-Cost Projects
In budget-sensitive projects, J55 is widely used for surface and technical casing due to its affordability and ample supply.
API 5CT J55 Casing Quality Inspection
Non-destructive testing: Surface and internal defects are detected using ultrasonic and magnetic particle testing to ensure the integrity of the casing.
Hydrostatic pressure test: Verifies sealing performance and prevents leakage risks.
Flattening test: Tests plastic deformation capacity to ensure the casing's adaptability in complex formations.
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