Drill Pipe & Drill String Components

The bottom hole assembly is comprised of a variety of components. The most pivotal being the drill bit. Connected to the drill bit is a drill collar, which is a heavy-weight tubular which provides lots of extra weight on the drill bit. The extra weight forced onto the drill bit allows for more efficient drilling through hard rock and other materials. Another critical component of the bottom hole assembly is the stabilizer, which helps keep the drill string in the center of the hole.

Transition pipe consists solely of heavy-weight drill pipe, which is attached to the Bottom Hole Assembly. The heavy weight drill pipe provides two functions, added weight to the drill bit for more efficient drilling, and a more durable drill pipe at the base of the drill string. The base of the drill string tends to be the most common area for fatigue failures, which is why heavyweight drill pipe is used in the section of the drill string.

Drill pipe comprises the vast majority of the drill string. A typical onshore drill string averages about 15,000 feet, while the average offshore drill string measures 30,000 feet. The standard drill pipe simply provides the length of the drill string, while the other components do the work.

Drill stem subs provide linkage of the other components in the drill string. Links between different components vary, however they all serve the same function, connecting the bits to the collars, collars to heavy pipe, and heavy pipe to standard pipe.