Specifications and dimensions of oil casing

Specifications and dimensions of oil casing

Oil casing specifications and dimensions

1. Domestic casing is in accordance with SY/T6194-96. The length of casing is not fixed, ranging from 8-13m. However, casing not shorter than 6m can be provided, and the number shall not exceed 20%.

2. There shall be no folds, hairlines, delamination, cracks, rolling and scarring on the inner and outer surfaces of the casing. These defects should be completely removed, and the removal depth shall not exceed 12.5% of the nominal wall thickness.

3. There shall be no defects such as folds, hairlines, delamination, cracks, rolling and scarring on the outer surface of the coupling.

4. The threaded surface of the casing and coupling shall be smooth, and burrs, tears and other defects that are sufficient to interrupt the thread and affect the strength and tight connection are not allowed.

Oil casing standard

API SPEC 5CT-2011 "Oil Pipe and Casing Specification" is a standard for oil casing issued by the American Petroleum Institute. It is universally used and is mainly used for oil pipes, tubing and casing.

Use of oil casing

Oil casing is a steel pipe used to support the well wall of oil and gas wells to ensure the normal operation of the entire oil well during the drilling process and after completion. Each well uses several layers of casing according to different drilling depths and geological conditions. After the casing is lowered into the well, cement cementing should be used. Unlike oil pipes and drill pipes, it cannot be reused and is a one-time consumable material. Therefore, the consumption of casing accounts for more than 70% of all oil well pipes. Casing end processing forms: short round thread, long round thread, trapezoidal thread, special buckle, etc. Used in oil well drilling, it is mainly used to support the well wall during the drilling process and after the completion of the well, so as to ensure the progress of the drilling process and the normal operation of the entire oil well after the completion.

The important position of oil casing

The oil industry is an industry that uses a large number of oil casings, and oil casings occupy a very important position in the oil industry:

1. Oil casings are used in large quantities and cost a lot of money, and there is huge potential for saving expenses and reducing costs. The consumption of oil well pipes can be calculated according to the annual drilling scale. According to the specific situation in my country, generally 62kg of oil well pipes are required for every 1m of drilling, including 48kg of casing and 10kg of oil pipes. Drill rods are 3kg and drill collars are 0.5kg;

2. The mechanics and environmental behavior of oil casings have an important impact on the adoption of advanced technology and increased production and efficiency in the oil industry;

3. The failure loss of oil casings is huge, and its safety, reliability and service life are of great importance to the oil industry.

Classification of oil casings

According to the use of casings, casings can be divided into: guide tubes, surface casings, technical casings and oil layer casings.

Different types of casing used in the oil production process:

Surface oil casing: protects the drilling well from pollution by shallow water and shallow gas layers, supports wellhead equipment and maintains the weight of other layers of the casing.

Technical oil casing: separates the pressure of different layers so that the drilling fluid can flow normally and protect the production casing, and installs anti-burst devices, leak-proof devices and tail pipes in the drilling well.

Oil layer oil casing: guides oil and natural gas out of the reservoir layer under the surface. Used to protect the drilling well and stratify the drilling mud. When the oil casing is produced, the outer diameter is usually 114.3 mm to 508 mm.

Types and packaging of oil casing are divided into short threaded casing and its couplings and long threaded casing and its couplings according to SY/T6194-96 "Oil Casing".

According to the strength of the steel itself, the casing can be divided into different steel grades, namely J55, K55, N80, L80, C90, T95, P110, Q125, V150, etc. Different well conditions and well depths require different steel grades. In corrosive environments, the casing itself is also required to have corrosion resistance. In places with complex geological conditions, the casing is also required to have anti-collapse performance.

Weight calculation

[(outer diameter-wall thickness)*wall thickness]*0.02466=kg/meter (weight per meter)

Chemical composition

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

(2) Take chemical analysis samples according to GB/T222-84. Conduct chemical analysis according to the relevant provisions of GB223;

(3) American Petroleum Institute API SPEC 5CT 1988 1st edition. Chemical analysis is carried out according to the latest version of ASTME59 and the latest version of ASTME350.

Physical properties

(1) According to SY/T6194-96. Flattening test (GB246-97), tensile test (GB228-2010) and water pressure test;

(2) According to the provisions of the American Petroleum Institute API SPEC 5 CT 1988, 1st edition, hydrostatic pressure test, flattening test, sulfide stress corrosion cracking test, hardness test (conducted according to the latest version of ASTM E18 or E10), tensile test, transverse impact test (conducted according to the latest version of ASTM A370, ASTM E23 and relevant standards), grain size determination (conducted according to the latest version of ASTM E112 or other methods).