Oil well casings are critical equipment for oil drilling operations, along with important components like drill pipes, core barrels, casings, drill collars, and small-diameter drill pipes. Domestically produced products are made from geological drill steel that undergoes hot rolling or cold drawing processes. The steel grades are designated with the prefix "DZ", and commonly used steel grades include DZ40, DZ55, and DZ75.
Applications
Used in oil well drilling operations.
Types
According to SY/T6194-96 "Petroleum Casing", there are two types: short-threaded with couplings and long-threaded with couplings.
Specifications and Surface Quality
(1) Per SY/T6194-96, domestic Oil well casings have non-uniform lengths ranging from 8-13m, but shorter than 6m can be provided not exceeding 20% of the total quantity.
(2) The inner and outer surfaces must be free from laps, seams, laminations, cracks, scoring, and die marks. These defects should be completely removed, with a depth not exceeding 12.5% of the nominal wall thickness.
(3) The coupling outer surface must not have laps, seams, laminations, cracks, scoring, or die marks.
(4) The casing and coupling thread surfaces should be smooth, with no burrs, tears, or other defects that could interrupt the threads, affecting strength and secure connections.
Chemical Composition Testing
(1) Per SY/T6194-96, casings and couplings use the same steel grade with sulfur ≤0.045% and phosphorus ≤0.045%.
(2) Chemical analysis samples taken per GB222-84, with chemical analysis conducted per relevant GB223 sections.
(3) Per API Spec 5CT 1988 1st Edition, chemical analysis samples prepared per latest ASTM E59, with analysis per latest ASTM E350.
Physical Property Testing
(1) Per SY/T6194-96, flattening tests (GB246-97), tensile tests (GB228-87), and hydrostatic tests conducted.
(2) Per API Spec 5CT 1988 1st Ed., hydrostatic, flattening, sulfide stress cracking, hardness (latest ASTM E18 or E10), tensile, Charpy impact (latest ASTM A370, E23 etc.), grain size (latest ASTM E112 or other) tests conducted.
Key Import/Export Summary
(1) Major casing import countries: Germany, Japan, Romania, Czech Republic, Italy, UK, Austria, Switzerland, USA; some from Argentina, Singapore. Imports often reference API 5A, 5AX, 5AC with steel grades H-40, J-55, N-80, P-110, C-75, C-95 etc. Common sizes like 139.7, 177.8, 244.5 mm OD.
(2) API specifies three length ranges: R-1 4.88-7.62m, R-2 7.62-10.36m, R-3 >10.36m.
(3) Some imports marked "LTC" for long thread couplings.
(4) Japanese imports sometimes use proprietary standards like NC-55E, NC-80E etc. from mills like Nippon Steel, Sumitomo, Kawasaki.
(5) Claims have involved defects like damaged threads/couplings, collapse, coupling separations, improper thread interference, improper coupling J measurements, as well as inherent issues like brittleness, low yield strength.
Other
Per API Spec 5CT 1988 1st Ed., Oil well casing steel grades include H-40, J-55, K-55, N-80, C-75, L-80, C-90, C-95, P-110, Q-125.
Casings supplied with threads and couplings, or with these end types:
Plain end, round threads with/without couplings, buttress threads with/without couplings, flush joint threads, special end preps, seal ring designs.
Vigor will provide you with a reliable solution, Please contact us at info@vigorpetroleum.com.
