Drill collar

Drilling Equipment & Components

Drill collars are thick-walled, heavy tubulars placed at the bottom of the drillstring, just above the bit. Their primary purpose is to provide weight on bit (WOB) to drill effectively and to keep the drillstring in tension to prevent buckling.

Collars are much stiffer than drill pipe, which helps keep the hole straight. They come in various designs, including slick (smooth) or spiraled (machined grooves to reduce wall contact and differential sticking risk). The transition from heavy collars to flexible drill pipe typically involves Heavy Weight Drill Pipe (HWDP).