Oil casing is an important equipment for oil drilling, including drill pipe, drill collar, steel pipe, core pipe and casing for small diameter drilling.  Domestic casing is made of geological drilling steel by hot rolling process or cold drawing process, the steel number is indicated by "geological" --DZ, commonly used casing steel  

DZ40, DZ55, DZ753.  

(1) According to SY/T6194-96 rules, the length of domestic oil casing is variable, and its scale is 8-13m.  However, sleeves not less than 6m can be provided, and the quantity shall not exceed 20%.  

(2) The inner and outer surface of the oil casing shall not be folded, wrinkled, separated, cracked, rolled and scarred.  These defects should be eliminated to a depth of no more than 12.5% of the nominal wall thickness.  

(3) the outer appearance of the collar shall not have folding, hair lines, separation, cracks, rolling, scarring and other shortcomings.  

(4) The outer surface of the oil casing and coupling threads should be lubricated, without burr, tear and other defects that can affect the strength and tight connection due to thread interruption.  

Oil casing is mainly used for drilling and transporting oil and gas Wells.  It contains oil drilling pipe, oil casing, extraction pipe.  The oil drill pipe is primarily used to connect the drill collar to the drill bit and transfer drilling power.  Casing is primarily used to support the well wall during drilling and after completion to ensure the drilling process and the normal operation of the well after completion.  The suction pipe primarily delivers oil and gas from the bottom of the well to the surface.  

Packing: According to SY/T6194-96, domestic sleeves should be bound with steel wire or steel belt. Maintenance rings shall be screwed on the exposed parts of each casing and collar thread to maintain the thread.