The drill collar is at the bottom of the drill string and is a major component of the lower hole assembly. Its main feature is that the wall thickness is large (generally 38~53mm, which is equivalent to 4~6 times of the wall thickness of the drill pipe), and it has greater gravity and rigidity. In order to facilitate the drilling work, the elevator slot and the slip groove can be processed on the outer surface of the internal thread of the drill collar.
Drill collar introduction
Made of rolled or forged AISI 4145H chrome-molybdenum alloy steel for effective control of chemical and trace element content.
Applying a weight to the drill bit;
To ensure the necessary strength under compression conditions;
Reducing the vibration, oscillation, and jumping of the drill bit, so that the drill bit works smoothly;
Control the well inclination.
Drill collars are generally divided into three types: auger drill collars, non-magnetic drill collars, and overall drill collars.
The overall drill collar is a smooth thick-walled round pipe, and the connecting threads are machined at both ends.
The spiral drill collar is machined with three right-handed spiral grooves on the outer cylindrical surface of the round drill to reduce the contact area with the well wall, which can effectively prevent the pressure difference stuck.
Non-magnetic drill collar is mainly used for monitoring during oil drilling, and the structure is the same as the overall drill collar. The non-magnetic drill collar is made of N1310 low carbon alloy steel, which is forged by rigorous chemical composition analysis. The material has been tested for mechanical properties to ensure hardness, toughness, impact and corrosion resistance in accordance with standards, with good low magnetic permeability and good machinability.
In order to facilitate the drilling work, the elevator slot and the slip groove can be processed on the outer surface of the internal thread of the drill collar.
Executive standard: SY5144-2007.API7-1