K55 Oil Casing

Oil casing is an important equipment used in petroleum drilling. Other main equipment includes drill rods, core tubes, casings, drill collars, and small-diameter drill pipes. Domestic casings are made of steel for geological drilling, processed by hot rolling or cold drawing, and the steel grade is indicated by 'DZ' (for geological use). Common casing steel grades are DZ40, DZ55, and DZ753. The types and packaging of oil casings are divided according to SY/T6194-96 'Oil Casings' into short-thread casings with couplings and long-thread casings with couplings. According to SY/T6194-96 standards, domestic casings should be bound with steel wire or steel tape. Protective rings must be screwed onto the exposed threads of every casing and coupling to protect the threads.

Oil casing specifications: 139.77.72R-2, 177.89.19R-2, 244.58.94R-2, 244.510.03R-2, 244.511.05R-2. R-1 is 4.88–7.62m, R-2 is 7.62–10.36m, and R-3 is 10.36m or longer.

Appearance Quality
1. Domestic casings, according to SY/T6194-96, have non-standard lengths ranging from 8–13m. Casings shorter than 6m can be provided, but the quantity must not exceed 20%.
2. The internal and external surfaces of the casing must not have folds, hairline cracks, delamination, cracks, roll marks, or scars. These defects must be completely removed, and the removal depth must not exceed 12.5% of the nominal wall thickness.
3. The external surface of couplings must not have folds, hairline cracks, delamination, cracks, roll marks, scars, or other defects.
4. The thread surfaces of casings and couplings should be smooth, with no burrs, tears, or other defects that could interrupt the threading, affecting strength and tight connections.

Chemical Composition Inspection
1. According to SY/T6194-96, casings and their couplings must use the same steel grade. Sulfur content <0.045%, phosphorus content <0.045%.
2. Chemical analysis samples are taken according to GB222-84. Chemical analysis is carried out according to the relevant sections of GB223.
3. According to the American Petroleum Institute APISPEC 5CT 1988, 1st edition. Chemical analysis samples are prepared according to the latest version of ASTM E59 and analyzed according to the latest version of ASTM E350.

Physical Performance Inspection
1. According to SY/T6194-96, perform flattening test (GB246-97), tensile test (GB228-87), and hydrostatic pressure test.
2. According to the American Petroleum Institute APISPEC 5CT 1988, 1st edition, perform hydrostatic test, flattening test, sulfide stress cracking test, hardness test (according to the latest version of ASTM E18 or E10), tensile test, transverse impact test (ASTM A370, ASTM E23 and relevant standards latest versions), and grain size determination (latest version of ASTM E112 or other methods).

Oil Casing Calculation Formula
(Outer diameter – Wall thickness) * Wall thickness * 0.02466 = kg/m (weight per meter)