Drilling rigs come in three sizes: singles, doubles and triples.

These categories refer to how many lengths of pipe can stand in the rig’s derrick. On a single, the derrick holds one length of pipe. A double holds two, and a triple holds three.

A tall derrick isn’t necessary to drill deeper. If more pipe is needed to drill deeper, a single section of pipe is hoisted to the rig floor and added to the drill string. But sometimes the entire drill string needs to be pulled out of the hole (to change the drill bit, for instance). A derrick that holds multiple lengths of pipe comes in handy and helps the crew to complete this evolution quickly.

A crew working on a triple is able to pull three lengths of pipe out of the hole before unscrewing the pipe. The derrickman, working from the monkeyboard, sets the ‘stand’ of pipe in the derrick. Then the crew pulls up the next three joints of pipe. This evolution is called ‘tripping’.

The larger derrick is efficient to drill deep wells but isn’t necessary for shallow wells.

Single rigs drill wells that are around 1 to 2 kilometres deep. These wells usually access gas basins. Single rigs and their crews change drilling locations often, sometimes every day or every other day. Crewmembers on singles complete the full cycle of a drilling operation many times in a month so they tend to get promoted faster than crewmembers on larger rigs.

Doubles and triples are larger rigs with bigger substructures and taller derricks.  These rigs drill between 3 and 6 kilometres into the earth. They might have additional crew members. (Crews on singles usually don't have leasehands or assistant drillers.) Doubles or triples might be at the same location for several months to complete deep drilling operations.

Singles, doubles and triples refer to conventional rig categories.  Additional new categories of rigs have introduced different ways of handling pipe.   For instance, some companies run coil-tubing rigs.  Coil-tubing rigs stream tubing from a large reel instead of using drill pipe.  Automated drilling rigs are outfitted with a pipe-handling arm that raises the pipe into the derrick, eliminating the need for a derrickhand to work from the monkeyboard.

Rig crews are tasked with hitting a specific point several kilometres underground. It’s not uncommon for a drilling target to be about the size of a kitchen table.

To complete a drilling program, the crew must pay precise attention to the position of the bit downhole. The crew’s experience and skill are critical in ensuring the well is drilled exactly as described by the drilling program.