N80 steel casing pipe

In the API SPEC 5CT casing pipe standard, the steel grade of casing and tubing indicates its yield strength and characteristics. Steel grade markings are usually represented by 1 letter and 2 or 3 numbers, such as N80. In most cases, according to the order of letters in the alphabet, the later the letter, the greater the yield strength of the pipe. For example, N80 grade steel casing pipe has a greater yield strength than J55: the numerical notation is determined by the minimum yield strength of the pipe expressed in thousands of pounds per square inch. For example: the minimum yield strength of N80 steel grade is 80klb/in2

The oil and casing steel grades listed in the API SPEC 5CT standard are: H40, J55, K55, N80, M65, L80, C90, C95, T59, P110, Q125.

1.What is N80 pipe?

N80 steel pipes are generally petroleum casing pipes. N80 oil casing is an important equipment for oil drilling. Its main equipment also includes drill pipes, core pipes and casings, drill collars and small-diameter drilling steel pipes.

2. Introduction to N80 steel casing pipe

(1)Use

N80 steel casing pipe is used in oil drilling and cementing operations.

(2)Type

According to SY/T6194-96 "Petroleum Casing", there are two types: short threaded casing and its couplings and long threaded casing and its couplings.

(3) Specifications and appearance quality

① China's domestic casing is stipulated in SY/T6194-96. The length of the casing is not fixed, and its range is 8-13m. However, casing not shorter than 6m can be provided, and its quantity shall not exceed 20%.

② The internal and external surfaces of the casing shall be free of folds, hairlines, separation layers, cracks, folds and scars. These defects should be completely removed to a depth not exceeding 12.5% of the nominal wall thickness.

③The outer surface of the coupling shall not have defects such as folds, hair lines, separation layers, cracks, folds, scars, etc.

④The thread surface of the casing and coupling should be smooth, and no burrs, tears or other defects sufficient to interrupt the threads will affect the strength and tight connection.

(4)Chemical composition inspection

①According to the regulations of SY/T6194-96. The casing and its couplings are of the same steel grade. Sulfur content <0.045%, phosphorus content <0.045%.

②Take chemical analysis samples according to the regulations of GB222-84. Carry out chemical analysis according to the relevant provisions of GB223.

③ American Petroleum Institute ARISPEC5CT1988 1st edition regulations. Chemical analysis was carried out according to the latest version of ASTME59 for sample preparation and chemical analysis according to the latest version of ASTME350.

(5) Physical performance inspection of N80 steel casing pipe

①According to the regulations of SY/T6194-96. Conduct flattening test (GB246-97), tensile test (GB228-87) and hydraulic pressure test.

② Carry out hydrostatic pressure test, flattening test, sulfide stress corrosion cracking test, hardness test (conducted according to the latest version of ASTME18 or E10), tensile test, and transverse impact test (ASTMA370, ASTME23 and the latest version of relevant standards), grain size determination (ASTME112 latest version or other methods).

(6)Packaging

According to SY/T6194-96, domestic casing should be bundled with steel wire or steel belt. A protective ring (wire protector) should be screwed on the exposed part of each casing and coupling thread to protect the thread.

(7)Others

According to the American Petroleum Institute standard APISPEC5CT 1988 1st edition, casing steel grades are H-40, J-55, K-55, N-80, C-75, L-80, C-90, C-95, P- There are 10 types of 110 and Q-125.

Casing shall be supplied with threads and couplings, or with any of the following pipe end forms:

Plain end, round thread without coupling or with coupling, trapezoidal thread with coupling or without coupling, direct connection thread, special end processing, sealing ring structure.

3. Casing produced in China

Domestic casing is made of hot-rolled or cold-drawn steel for geological drilling. The steel grade is represented by "geology" (DZ). Commonly used casing steel grades include DZ40, DZ55, and DZ753.

(1) The main importing countries of oil casing are: Germany, Japan, Romania, the Czech Republic, Italy, the United Kingdom, Austria, Switzerland, the United States, and Argentina and Singapore also import. Import standards mostly refer to the American Petroleum Institute standards API5A, 5AX, and 5AC. Steel grades are H-40, J-55, N-80, P-110, C-75, C-95, etc. The main specifications are 139.77.72R-2, 177.89.19R-2, 244.58.94R-2, 244.510.03R-2, 244.511.05R-2, etc.

(2) API specifies three lengths: R-1 is 4.88~7.62m, R-2 is 7.62~10.36m, and R-3 is 10.36m or longer.

(3) Some imported goods are marked with LTC, which means long threaded casing.

(4) In addition to API standards, casing imported from Japan also adopts Japanese factory standards (such as Nippon Steel, Sumitomo, Kawasaki, etc.). The steel numbers are NC-55E, NC-80E, NC-L80. NC-80HE etc.

(5) In the claim cases, there have been appearance defects such as black buckles and threaded buckle damage, folding of the pipe body, broken buckles, excessive thread tightness, excessive coupling J value, and internal defects such as casing brittleness and low yield strength. quality problem.

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