Oil casing applications:
Used for oil well drilling is mainly used in the drilling process and after the completion of the well wall support, in order to ensure the drilling process and the normal operation of the whole well after the completion.Due to the different geological conditions, the underground stress state is complex, and the comprehensive action of tensile, compressive, bending and torsional stresses on the pipe body puts forward higher requirements for the quality of the casing itself.Once the casing itself is damaged due to some reason, it may lead to the production reduction of the whole well, or even scrap.
Types of oil casing:
According to SY/T6194-96 “petroleum casing”, it can be divided into two kinds: short threaded casing and its collar and long threaded casing and its collar.
Oil casing standard and packaging:
According to SY/T6194-96, domestic casing should be tied with steel wire or steel belt.The exposed part of each casing and collar thread should be screwed with a protective ring to protect the thread.
The casing shall be supplied with thread and collar according to API SPEC 5CT1988 first edition or in any of the following pipe end forms: flat end, round thread without collar or collar, offset trapezoidal thread with or without collar, straight thread, special end processing, seal ring construction.
Steel grade for petroleum casing:
Oil casing steel grade can be divided into different steel grades according to the strength of the steel itself, namely H-40, J-55, K-55, N-80, C-75, L-80, C-90, C-95, P-110, Q-125, etc.Different well conditions, well depth, the use of steel grade is also different.The casing itself is also required to be corrosion-resistant in corrosive environments.In places with complex geological conditions, the casing is also required to be resistant to crush.
The weight calculation formula of oil casing is as follows:
KG/ m = (outer diameter – wall thickness) * wall thickness *0.02466
Oil casing length:
There are three types of length specified by API: R-1 4.88 to 7.62m, R-2 7.62 to 10.36m, R-3 10.36m to longer.
Petroleum casing buckle type:
API 5CT petroleum casing buckle types include STC (short round buckle), LTC (long round buckle), BTC (partial ladder buckle), VAM (king buckle) and other buckle types.
Physical performance inspection of petroleum casing:
(1) According to SY/T6194-96.To perform flattening test (GB246-97) tensile test (GB228-87) and hydrostatic test.
(2) hydrostatic test, flattening test, sulfide stress corrosion cracking test, hardness test (ASTME18 or E10 latest version), tensile test, transverse impact test (ASTMA370, ASTME23 and the latest version of the relevant standards) according to the provisions of the American Petroleum Institute APISPEC5CT1988 first edition Ok), determination of grain size (ASTME112 latest version or other method)
Oil casing import and export:
(1) The main import countries of oil casing are: Germany, Japan, Romania, Czech Republic, Italy, the United Kingdom, Austria, Switzerland, the United States, Argentina, Singapore also import.Import standards refer to American Petroleum Institute standard API5A, 5AX, 5AC.Steel grade is H-40, J-55, N-80, P-110, C-75, C-95 and so on.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) There are three kinds of length specified by API: R-1 is 4.88 ~ 7.62m, R-2 is 7.62 ~ 10.36m, R-3 is 10.36m to longer.
(3) Part of the imported goods are marked with LTC, i.e., filament buckle sleeve.
(4) In addition to API standards, a small number of bushing imported from Japan comply with the standards of Japanese manufacturers (such as Nippon Steel, Sumitomo, Kawasaki, etc.), steel numbers are NC-55E, NC-80E, NC-L80, NC-80HE, etc.
(5) In the claim cases, there were appearance defects such as black buckle, wire tie damage, pipe body folding, broken buckle and thread tight distance out of tolerance, coupling J value out of tolerance, and internal quality problems such as brittle cracking and low yield strength of the casing.
Mechanical properties of each steel class of petroleum casing:
|
standard |
brand |
Tensile strength (MPa) |
Yield strength (MPa) |
Elongation (%) |
hardness |
|
API SPEC 5CT |
J55 |
P 517 |
379 ~ 552 |
Look-up table |
|
|
K55 |
P 517 |
P 655 |
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|
N80 |
P 689 |
552 ~ 758 |
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|
L80(13Cr) |
P 655 |
552 ~ 655 |
241 hb or less |
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|
P110 |
P 862 |
758 ~ 965 |