Drilling tools & tubing
The main component of the lower drilling tool assembly
Drill collar is in the lowest part of the drill pipe, and is the main component of the lower drilling tool combination. It is mainly characterized by its large wall thickness (generally 38~53mm, equivalent to 4~6 times of the wall thickness of the drill pipe) and large gravity and stiffness. In order to facilitate the work of up and down drilling, the outer surface of the inner thread of the drill collar can be processed in the hanger groove and kava groove.
(1) Apply drilling pressure to the drill bit.
(2) Ensure the necessary strength under compression conditions.
(3) Reduce the vibration, swing, and runout of the drill bit to make the drill bit work smoothly; and
(4) Control the well inclination.
Drill collars are generally divided into three types: spiral drill collars, non-magnetic drill collars, and integral drill collars.
(1) The whole drill collar is a smooth thick-walled round tube with threaded ends.
(2)The spiral drill collar has 3 right-handed spiral grooves on the outer cylindrical surface of the collar to reduce the contact area with the well wall, which can effectively prevent the differential pressure from jamming the drill.
(3)The non-magnetic drill collar is mainly used for monitoring during oil drilling, and the structure is the same as the whole drill collar. The non-magnetic drill collar is made of N1310 low carbon alloy steel, which is forged after strict chemical composition analysis. The material has been tested for mechanical properties to ensure that the hardness, toughness, impact value and corrosion resistance are in accordance with the standard, with good low magnetic permeability and good machinability.
In order to facilitate the work of up and down drilling, the outer surface of the inner thread of the drill collar can be machined with hanger slots and kava slots.