Glossary
Appraisal well A well drilled to determine the extent and size of a petroleum discovery.
Blowout preventer (BOP) A large valve installed on top of a well which can be closed if the drilling crew loses control of the well (blowout).
Christmas (Xmas) tree A assembly of pipes and valves installed on a wellhead.
Derrick The steel tower which carries the drill string during drilling operations.
Drill bit Attached to the end of the drill string. It is fitted with rotating teeth which bite their way through the rock during drilling.
Drill string A series of steel pipes screwed together, which link the drill bit with the drill rig. Each pipe is usually about 10 metres long. The string rotates and also conducts mud during the drilling operation.
Drilling mud (fluids) A blend of chemicals and clay with water or oil used to lubricate and cool the drill bit, prevent the well from collapsing, keep possible oil and gas flows under control and transport drill cuttings (rock chips) to the surface.
Injection well A well used for injecting gas or water to provide pressure support in a reservoir. Injection below an oil or gas zone helps to maintain pressure.
Multilateral well A well where several branches (sidetracks) have been drilled out through the wall of the original borehole.
Production well A well used to recover petroleum from a reservoir.
Roughneck A drill floor worker, who performs heavy manual operations related to drilling. An iron roughneck is an automated system which has taken over many of the heaviest and most dangerous jobs on the drill floor.
Spud The first step in drilling a well, and the period when the drill bit first penetrates the seabed. Spud fever: an informal term for the hectic period immediately before a well is spudded.
Toolpusher The drilling contractor’s representative on the rig. Monitors progress with the drilling process, and ensures that the right people and equipment are in place at all times to do the work.
Top drive A motor suspended in the derrick to rotate the drill string as it penetrates the seabed.
Wildcat/exploration well The first well drilled on a completely new, clearly defined geological structure (prospect).