A drill collar is a thick-walled, heavy, and short section of drill pipe that is added to the bottom of the drill string to provide weight on the bit. It is typically made of high-strength steel, such as alloy steel or tungsten carbide. Drill collars are used to help keep the drill string straight and to provide a means of transmitting drilling torque to the bit.

The drill collar is located in the lower part of the drill string and is the main part of the lower drill tool assembly. Its main feature is that the wall thickness is relatively large (generally 38-53mm, which is equivalent to 4-6 times the wall thickness of the drill pipe), and it has greater gravity and rigidity. Drill collars are generally divided into three types: spiral drill collars, non-magnetic drill collars, and integral drill collars.

Drill collars are generally divided into three types: spiral drill collars, non-magnetic drill collars, and integral drill collars.