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Eastern Steel Manufacturing Co.,Ltd is a leading manufacturer and distributor of seamless steel pipe, welded steel pipe, OCTG products and fittings. We supply first-step processing, semi-finished parts and finished parts to help our clients meet fabrication requirements beyond their capacity or to improve operations by moving forward the pre-production processing.
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Oil casing pipe is an important OCTG pipe in oil drilling, mainly used to control the pressure of the wellhead section and protect the oil layer environment. OCTG casing is usually made of steel pipe, and the quality and performance are directly related to the effect and safety of oil field exploitation.
Casing pipe implementation standard
1. API SPEC 5CT
API SPEC 5CT is the technical specification for oil casing pipe formulated by the American Petroleum Institute and is one of the mainstream standards adopted by the global oilfield industry. The standard specifies the basic technical requirements such as the size, steel type, mechanical performance index and chemical composition of oil casing pipe, as well as the contents of marking, packaging, quality control, etc. The API SPEC 5CT standard is applicable to the manufacture and use of ordinary casing pipe, cement casting casing, anti-corrosion casing pipe and other types of oil casing pipe.
2. ISO 11960
ISO 11960 is a steel line pipe specification issued by the International Organization for Standardization, which is also widely used in the field of oil and gas drilling and exploitation. The standard requires that the technical parameters of the oil casing pipe, such as size, steel type, mechanical properties and chemical composition, meet the requirements, and provides detailed descriptions on integrity, customer requirements, performance acceptance, etc. ISO 11960 also includes 4 different grades of oil casing pipe, namely P110, Q125, C90 and T95, which are used to adapt to different working environments and requirements.
3. GOST
GOST is the Russian oil casing pipe standard, and the standard number is GOST R 53366-2009. This standard is different from API SPEC 5CT and ISO 11960, mainly in the manufacturing process and material selection of oil casing pipe. The GOST standard is applicable to oil casing pipe under special working conditions such as high pressure resistance, high corrosion resistance and high temperature, and is also the mainstream standard of the Russian oilfield industry.
API SPEC 5CT OCTG casing
According to the API 5CT specification, the size standards of OCTG casing mainly include the following aspects:
1. Outer diameter (OD)
According to the API 5CT specification, the outer diameter of OCTG casing can range from 2.375 inches to 20 inches, among which the common outer diameters are 4.5 inches, 5 inches, 5.5 inches, 7 inches, etc.
2. Wall thickness
The wall thickness of OCTG casing varies according to different outer diameters and materials, usually ranging from 0.224 inches to 1.000 inches.
3. Steel grade
The API 5CT specification defines multiple steel grades for OCTG casing, including H40, J55, K55, N80, L80, C90, T95, P110, etc. Different steel grades have different mechanical properties and corrosion resistance.
4. Connection method
The API 5CT specification also stipulates the connection method of casing, including external thread (EUE) and internal thread (NU). These connection methods can meet the different requirements of casing in well construction and oil and gas production.
5. Length
API 5CT specification stipulates that the length of OCTG casing is within the range, usually R1 (18-22 feet), R2 (27-30 feet) and R3 (38-45 feet).
Mechanical properties of API 5CT OCTG casing
|
Standard |
Grade |
Tensile strength（MPa） |
Yield strength（Mpa） |
Hardness |
|
API SPEC 5CT |
J55 |
≥517 |
379-552 |
|
|
K55 |
≥517 |
≥655 |
|
|
|
N80 |
≥689 |
552-758 |
|
|
|
L.80(13Cr) |
≥655 |
552-655 |
≤241HB |
|
|
P110 |
≥862 |
758-965 |
|
Chemical composition of API 5CT OCTG casing
|
Standard |
Grade |
Chemical composition（%） |
||||||||||
|
C |
Si |
Mn |
P |
S |
Cr |
Ni |
Cu |
Mo |
V |
Als |
||
|
API SPEC 5CT |
J55K55 (37Mn5) |
0.34~0.39 |
0.20~0.35 |
1.25~1.50
|
≤0.020
|
≤0.015 |
≤0.15 |
≤0.20 |
≤0.20 |
/ |
/ |
≤0.20 |
|
N80(36Mn2V) |
0.34~0.38 |
0.20~0.35 |
1.45~1.70 |
≤0.020 |
≤0.015 |
≤0.15 |
/ |
/ |
/ |
|
≤0.020 |
|
|
L80(13Cr) |
0.15~0.22 |
≤1.00 |
0.25~1.00 |
≤0.020 |
≤0.010 |
12.0~14.0 |
≤0.20 |
≤0.20 |
/ |
/ |
≤0.020 |
|
|
P110(30CrMo) |
0.26~0.35 |
0.17~0.37 |
0.40~0.70 |
≤0.020 |
≤0.010 |
0.80~1.10 |
≤0.20 |
≤0.20 |
0.15~0.25 |
≤0.08 |
≤0.020 |
|
Dimensional deviation of API 5CT OCTG casing
|
Dimensional deviation |
||
|
Item |
Permissible deviation |
|
|
Outer diameter |
Pipe body |
D<101.60mm±0.79mm |
|
D>114.30mm+1.0% -0.5% |
||
|
|
||
|
Wall thickness |
-12.5% |
|
|
Weight |
Single piece |
+6.5% |
|
+3.5% |
||
|
Car load |
-1.75 |
|
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