Drill String is. Points of Drill String

Drill String

• The drillstring is made up of the drillpipe, drill collars, and specialized subs through which the drilling fluid and rotational power are transmitted from the surface to the bit.
• Drill pipe and drill collar come in sections, or joints, about 30 feet long.
• The most commonly used diameters of drill pipe are 4, 4½, and 5 inches OD.
• The purpose of drill collars is to put extra weight on he bit, so they are usually larger in diameter than drill pipe and have thicker walls.
• Drill pipe and drill collars have threaded connection on each end.
• On drill pipe the threaded connection are called tool joints. Tool joints are steel rings that are welded to each end of a joint of drill pipe. One tool joints is a pin (male) connection, and the other is a box (female) connection.
• Specialized Subs: The word “sub” refers to any short length of pipe, collar, casing, etc., with a definite function.