Brief introduction of petroleum casing for oil wells:
Petroleum casing for oil wells is a kind of steel pipe used to support the wall of oil and gas wells, which is mainly used to ensure the smooth running of the drilling process oil and the normal operation of the wells after completion. Due to the different drilling depths and geological conditions of each well, it is usually necessary to use multiple layers of casing. After the casing is lowered, it is also cemented. Unlike tubing and drill pipe, casing cannot be reused and is a disposable consumable material. As a result, casing accounts for more than 70% of oil and gas well tubing consumption.
Structure of Petroleum Casing:
1.Tubing Body: Provides structural support to withstand pressure and stress in drilling and production.
2、Threaded connection: Threads at both ends are used to connect multiple pieces of casing to form a complete wellbore. Thread types include long circular thread (LC), short circular thread (SC) and partial trapezoidal thread (BC) to meet different strength and sealing needs.
3. Coupling (if any): to enhance the strength and sealing of the connection, usually made of the same steel grade as the tubing body.
4、Coating or anti-corrosion treatment (optional): Some casing will be coated with anti-corrosion treatment or corrosion-resistant materials according to the use of the environment, in order to extend the service life, especially for the corrosive environment containing hydrogen sulfide (H₂S) or carbon dioxide (CO₂).
Petroleum casing specification sheet:
| Outer Diameter (OD) | Wall Thickness (WT) | Applicable Steel Grade | Notes |
|---|---|---|---|
| 2 7/8" (73.02mm) | 0.154" (3.91mm) | J55, N80 | For shallow and medium-depth wells |
| 3 1/2" (88.9mm) | 0.203" (5.16mm) | J55, N80 | For medium-depth wells |
| 4 1/2" (114.3mm) | 0.250" (6.35mm) | N80, P110 | For deep wells |
| 5 1/2" (139.7mm) | 0.322" (8.18mm) | N80, P110 | For deep wells |
| 7" (177.8mm) | 0.462" (11.73mm) | L80, P110 | For complex geological conditions |
| 9 5/8" (244.5mm) | 0.656" (16.66mm) | L80, P110 | For ultra-deep wells |
| 13 3/8" (339.7mm) | 0.750" (19.05mm) | L80, P110 | For extreme environments |
| 17 1/2" (444.5mm) | 0.910" (23.12mm) | L80, P110 | For ultra-deep wells and high-pressure environments |
| 20" (508mm) | 1.000" (25.4mm) | L80, P110 | For extreme environments and special applications |
Description:
Outside Diameter (OD): available in both inches and millimeters for easy reference by international users.
Wall Thickness (WT): adjusted according to application scenarios and steel grades to ensure that different well depths and geological conditions are met.
Applicable steel grades: Covering a wide range of steel grades from shallow wells to ultra-deep wells to meet different strength and corrosion resistance requirements.
Remarks: A brief description of the applicable scenarios to help users quickly choose the right product.
Steel grades and properties:
| Steel Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Hardness (HB) | Chemical Composition (mass fraction %) |
|---|---|---|---|---|
| J55 | 379-552 | ≥517 | ≤241 | C: 0.20-0.34, Mn: 0.60-1.25 |
| N80 | 552-758 | ≥689 | ≤241 | C: 0.20-0.34, Mn: 0.60-1.45 |
| L80 (13Cr) | 552-655 | ≥655 | ≤241 | C: 0.15-0.25, Cr: 12.0-14.0 |
| P110 | 758-965 | ≥862 | ≤241 | C: 0.26-0.35, Mo: 0.70-1.10 |
Specification and Performance of Petroleum Casing：
1. Weight Calculation
The formula for calculating the weight of petroleum casing is as follows:
Weight per meter (kg/m) = [(O.D.-Wall Thickness)×Wall Thickness]×0.02466
where the unit of O.D. and Wall Thickness are millimeters (mm).
2. Chemical composition
The chemical composition of petroleum casing strictly follows the following standards:
According to SY/T 6194-96: the casing and its joints are made of the same grade of steel, with sulfur content <0.045% and phosphorus content <0.045%.
Sampling according to GB/T 222-84: chemical analysis is carried out according to the relevant part of GB 223.
According to API SPEC 5CT: chemical analysis is made according to the latest version of ASTM E59 and analyzed according to the latest version of ASTM E350.
3. Physical properties
The physical property test of oil casing follows the following standards:
According to SY/T 6194-96: Flattening test (GB 246-97), tensile test (GB 228-2010) and hydraulic test.
According to API SPEC 5CT: Hydrostatic test, flattening test, sulfide stress corrosion cracking test, hardness test (according to the latest version of ASTM E18 or E10), tensile test, transverse impact test (according to the latest version of ASTM A370, ASTM E23 and other related standards), grain size determination (according to the latest version of ASTM E112 or other methods).
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