Anatomy of a drilling rig: 20 key components

Whether it's a land super-spec rig or an offshore jackup, every rotary drilling rig is organized around the same five systems. Learn the systems and the individual components fall into place. Below, each component is mapped to its system and its job.

Hoisting system: lifting the load

The hoisting system raises and lowers the drill string and casing — sometimes hundreds of tons of it.

• 1. Derrick / mast. The tall steel tower that supports the equipment and provides the height to handle stands of pipe.
• 2. Substructure. The steel base that carries the derrick and rig floor and creates working space beneath for the wellhead and BOP.
• 3. Drawworks. The big hoisting winch — a powerful spooling drum that reels the drilling line in and out to raise and lower the load.
• 4. Crown block. A fixed set of sheaves at the very top of the derrick.
• 5. Traveling block. A movable set of sheaves that rides up and down; with the crown block it forms a block-and-tackle that multiplies the drawworks' pulling power.
• 6. Drilling line. The heavy wire rope strung between crown and traveling blocks that actually carries the load.

Rotating system: turning the bit

The rotating system spins the drill string so the bit cuts downward into the rock.

• 7. Top drive. A motor that hangs in the derrick and rotates the drill string from the top while also handling pipe. On modern rigs the top drive has replaced the older kelly-and-rotary-table method, drilling longer intervals and improving well control.
• 8. Rotary table. The older turntable in the rig floor that rotated the string via the kelly; still present on many rigs and used for slips and tong work.
• 9. Kelly. The square or hexagonal pipe that the rotary table gripped to transmit rotation — largely superseded by the top drive.
• 10. Swivel. On kelly rigs, the component that hangs from the traveling block, lets the string rotate while staying still itself, and pipes mud in (the top drive integrates this function).
• 11. Drill string. The whole column of pipe and tools from surface to bit.
• 12. Drill pipe. The bulk of the string — jointed steel pipe that transmits rotation and mud.
• 13. Bottom-hole assembly (BHA). The lower end of the string: drill collars, stabilizers, and downhole tools just above the bit.
• 14. Drill collars. Heavy, thick-walled pipe in the BHA that puts weight on the bit and keeps the string in tension above.
• 15. Drill bit. The cutting tool at the bottom. Two main families: PDC (polycrystalline diamond compact, fixed-cutter) and tricone (roller-cone) bits — see the callout.

Circulating system: moving the mud

Drilling fluid (mud) is pumped down the string, out the bit, and back up the annulus — cooling the bit, carrying cuttings to surface, and holding back formation pressure.

• 16. Mud pumps. High-pressure reciprocating pumps that drive the mud down the drill string; super-spec rigs run high-pressure pumps for long laterals.
• 17. Mud / circulation system. The tanks, lines, and mud pits that store, mix, and condition the fluid before it's pumped again.
• 18. Solids control (shale shakers). Vibrating screens (shakers) plus desanders, desilters, and centrifuges that strip drilled cuttings out of the returning mud so it can be reused.

Well-control & power systems

The last two systems keep the well safe and keep everything running. Well control is the most critical safety function on the rig.

• 19. Blowout preventer (BOP). A stack of valves at the wellhead that can seal the well to stop an uncontrolled flow — the primary well-control barrier. Full BOP guide →
• 20. Choke manifold. A set of valves and chokes that lets the crew circulate out a kick under controlled back-pressure, working together with the BOP.
• Wellhead. The pressure-containing equipment at surface (or seabed) that the BOP connects to and that the casing strings hang from.
• Power system. The engines and generators (and, on AC rigs, drives) that supply power to the drawworks, top drive, and mud pumps — see land rig classes for mechanical vs SCR vs AC.

Common questions