Reference
The oil & gas drilling glossary.
96 rig, drilling, role, and commercial terms — defined clearly and accurately. Search, or jump by letter.
A
- AC rigEquipment
- A land rig powered by alternating-current drives, offering precise control well-suited to horizontal and pad drilling.
- AFECommercial
- Authorization for Expenditure — the cost estimate and budget-approval document an operator and partners sign off before drilling or major well work.
- AnnulusDrilling
- The space between two concentric strings, such as between the wellbore wall and casing, or between casing and tubing.
B
- BHAEquipment
- Bottom-hole assembly — the lower part of the drill string, including the bit, drill collars, stabilizers, and downhole tools such as the mud motor and MWD.
- Bit (drill bit)Equipment
- The cutting tool at the bottom of the drill string; either a roller-cone (tricone) or fixed-cutter (PDC) bit.
- BlowoutSafety
- An uncontrolled release of formation fluids from a well to surface.
- Blowout preventer (BOP)Equipment
- A stack of valves and rams at the wellhead that can seal the well to prevent a blowout; the rig's primary well-control barrier.
- BOECommercial
- Barrel of oil equivalent — a unit converting natural gas and NGLs into an equivalent volume of oil for combined reporting.
C
- CasingDrilling
- Steel pipe run and cemented in the hole to stabilize the wellbore and isolate formations.
- CementingDrilling
- Pumping cement into the annulus to bond casing in place and provide zonal isolation between formations.
- Choke manifoldEquipment
- An arrangement of valves used to control flow and back-pressure when circulating a kick out of the well.
- Cold-stackedCommercial
- A rig idled with most systems shut down and a minimal crew to cut cost; reactivation is slower and more expensive than from warm-stacked status.
- Company ManRoles
- The operator's senior on-site representative, with ultimate authority over the well, the drilling program, and the budget. Also called the Well Site Supervisor.
- CompletionDrilling
- The set of operations that turn a drilled hole into a producing well — casing, perforating, hydraulic fracturing, tubing, and wellhead installation.
- Compliant towerEquipment
- A slender, flexible offshore platform that withstands lateral loads by deflecting, used in roughly 1,000–2,000 ft of water.
- ConnectionDrilling
- Adding a joint or stand of pipe to the drill string as the hole deepens.
- Crown blockEquipment
- The fixed set of sheaves at the top of the derrick over which the drilling line is reeved.
D
- Day rateCommercial
- A fixed daily fee paid to a contractor or consultant for each day worked, used instead of an hourly wage or salary; for an independent it must cover taxes, insurance, and downtime.
- Decline curveCommercial
- The characteristic drop in a well's production rate over time; the steep early decline of shale wells drives the need for continuous drilling.
- DerrickEquipment
- The tall load-bearing tower that supports the hoisting system; a mast is a portable, hinged equivalent common on land rigs.
- DerrickhandRoles
- The crew member who works the monkeyboard high in the derrick handling the top of the drill string during trips, and tends the mud system.
- Directional DrillerRoles
- The specialist who steers the wellbore along its planned path using a mud motor or rotary steerable system, directing the MWD hand.
- Directional drillingDrilling
- Steering a wellbore along a planned non-vertical trajectory.
- DrawworksEquipment
- The main hoisting winch that spools drilling line to raise and lower the traveling block and drill string.
- Drill collarEquipment
- Heavy thick-walled pipe above the bit that provides weight-on-bit and keeps the bottom-hole assembly in compression.
- Drill pipeEquipment
- Threaded hollow steel joints that make up most of the drill string and convey drilling mud to the bit.
- Drill stringEquipment
- The full assembly of drill pipe plus the bottom-hole assembly connecting the surface to the bit.
- DrillerRoles
- The crew chief on the rig floor who operates the drilling controls and is responsible for the safety of the floor crew.
- DrillshipEquipment
- A ship-shaped, usually dynamically positioned vessel equipped to drill in deep and ultra-deepwater, well beyond 10,000 ft of water.
- Dynamic positioning (DP)Equipment
- Thruster-based station-keeping that holds a floating rig on location without anchors.
E
- E&PCommercial
- Exploration and production — the upstream business of finding and producing oil and gas.
- ERDDrilling
- Extended-reach drilling — drilling wells with very long horizontal departure relative to their vertical depth.
F
- FishingDrilling
- The operation of recovering stuck or lost tools or pipe (the fish) from the wellbore.
- Fishing Tool SupervisorRoles
- A specialist consultant called in to retrieve stuck or lost equipment from the wellbore; a high-skill, intermittent, premium-rate role.
- Fixed platformEquipment
- A permanent seabed-anchored structure that supports drilling and production in shallow-to-mid water.
- FloorhandRoles
- A drill-floor worker, also called a roughneck, who handles pipe and makes and breaks connections.
- FracDrilling
- Hydraulic fracturing — pumping fluid and proppant at high pressure to fracture rock and stimulate flow during completion.
H
- Henry HubCommercial
- The benchmark US natural-gas pricing point in Louisiana, referenced by most US gas contracts.
- HitchRoles
- One complete on-duty rotation on a rig, such as a 14-day hitch, before the off-duty period begins.
- Horizontal drillingDrilling
- Turning the wellbore to roughly 90 degrees to expose long sections of reservoir; central to shale development.
- HPHTDrilling
- High-pressure / high-temperature wells that require specialized equipment and fluids.
- HSE ConsultantRoles
- A specialist who manages on-site health, safety, and environmental compliance, permits, and drills.
J
- Jackup rigEquipment
- A bottom-supported offshore rig with a floating hull and three or more legs jacked down to the seabed, used in water typically up to ~120–150 m.
K
- KellyEquipment
- A square or hexagonal pipe that transmits rotation from the rotary table to the drill string on conventional rigs.
- KickSafety
- An unintended influx of formation fluid into the wellbore; an early warning of a potential blowout.
L
- LateralDrilling
- The horizontal section of a wellbore drilled through the target formation; modern laterals commonly reach 2–3+ miles.
- Lost circulationDrilling
- Loss of drilling fluid into the formation instead of returning to surface.
- LWDDrilling
- Logging-while-drilling — downhole formation-evaluation measurements taken in real time while drilling.
M
- Managed pressure drilling (MPD)Drilling
- A closed-loop drilling method using a rotating control device and choke to precisely control annular pressure.
- MastEquipment
- A portable, hinged derrick that can be raised and lowered for transport, common on land rigs.
- MD / TVDDrilling
- Measured depth is the length of the wellbore along its path; true vertical depth is the straight-line vertical depth. They diverge sharply in horizontal wells.
- MODUEquipment
- Mobile Offshore Drilling Unit — the umbrella term for moveable offshore rigs such as jackups, semis, and drillships.
- MonkeyboardEquipment
- The elevated platform in the derrick where the derrickhand handles the upper end of the pipe stands.
- MSACommercial
- Master Service Agreement — the pre-negotiated contract setting payment, indemnity, insurance, and liability terms for a contractor's repeated work for an operator.
- Mud (drilling fluid)Drilling
- The circulated fluid that lifts cuttings, cools and lubricates the bit, and exerts hydrostatic pressure to control the well.
- Mud EngineerRoles
- The specialist who designs and maintains the drilling-fluid system's density, rheology, and chemistry.
- Mud LoggerRoles
- A geology service hand who examines drill cuttings and gas readings to log formations and hydrocarbon shows.
- Mud pumpEquipment
- A high-pressure reciprocating pump that circulates drilling fluid down the string and up the annulus.
- MWDDrilling
- Measurement-while-drilling — real-time downhole directional and drilling data telemetered to surface.
N
- NGLCommercial
- Natural gas liquids — hydrocarbon liquids such as ethane, propane, and butane separated from natural gas.
- NPTCommercial
- Non-productive time — rig time lost when operations stop without adding value, such as equipment failure, stuck pipe, or weather.
O
- OIMRoles
- Offshore Installation Manager — the most senior person in charge of an offshore installation, with overall responsibility for the unit and personnel.
P
- P&ADrilling
- Plug and abandonment — permanently sealing a well at end of life with cement plugs and removing surface equipment.
- Pad drillingDrilling
- Drilling multiple wells from a single surface location by walking the rig between slots; standard practice in shale.
- PDC bitEquipment
- A fixed-cutter drill bit using polycrystalline-diamond-compact cutters.
- Per diemRoles
- A daily travel and expense allowance paid in addition to a day rate to cover lodging and meals.
- ProppantDrilling
- Sand or engineered particles pumped during fracturing to hold the fractures open so hydrocarbons can flow.
R
- Rig countCommercial
- A tally of active drilling rigs; the Baker Hughes Rig Count is the standard industry benchmark, published weekly since 1944.
- Rig ManagerRoles
- The drilling contractor's manager responsible for a rig as a business unit; above the toolpusher.
- Rotary tableEquipment
- A floor-mounted rotating table that turns the drill string via the kelly bushing on conventional rigs.
- RoughneckRoles
- A drill-floor worker who handles pipe and makes and breaks connections; the core manual drilling crew.
- RoustaboutRoles
- An entry-level general laborer who maintains the location and assists all crews; the typical way into rig work.
- RSSDrilling
- Rotary steerable system — a downhole tool that steers the bit while the entire string continues to rotate, used for precise directional drilling.
S
- SCR rigEquipment
- A land rig using silicon-controlled rectifiers to power DC motors; less precise than an AC rig.
- SemisubmersibleEquipment
- A floating rig that derives buoyancy from submerged pontoons under columns, moored or dynamically positioned for deepwater.
- SparEquipment
- A deep, large-diameter vertical-cylinder floating platform used for deepwater drilling and production.
- Spread rateCommercial
- The total combined daily cost of all the rig, services, equipment, and personnel running concurrently on a well; what every operating day, or day of NPT, actually costs.
- SpudDrilling
- To begin drilling a well; the bit's first penetration of the ground.
- Stuck pipeDrilling
- A condition where the drill string can no longer be moved in the hole; a top operational hazard.
- SubstructureEquipment
- The steel base that elevates the rig floor and provides space for the BOP stack beneath.
- Super-spec rigEquipment
- A high-spec AC land rig — typically 1,500+ hp, ~750,000+ lb hookload, with a walking system and high-pressure pumps — optimized for long-lateral pad drilling.
- SwivelEquipment
- The component below the hook that allows the drill string to rotate while admitting mud from the standpipe hose.
T
- TDDrilling
- Total depth — the final depth a well is drilled to.
- Tension-leg platform (TLP)Equipment
- A floating platform held by vertical tensioned tendons that suppress heave, used to roughly 5,000–7,000+ ft of water.
- Tight oil / shaleCommercial
- Oil or gas held in low-permeability rock that requires horizontal drilling and hydraulic fracturing to produce economically.
- ToolpusherRoles
- The drilling contractor's senior on-site supervisor, responsible for the entire rig's day-to-day operation.
- Top driveEquipment
- A suspended motor that rotates the drill string directly, replacing the kelly and rotary table.
- Traveling blockEquipment
- The moving sheave assembly that raises and lowers the drill string, reeved to the crown block.
- TrippingDrilling
- Pulling the drill string out of the hole or running it back in, commonly to change the bit or run tools.
U
- UpstreamCommercial
- The exploration and production segment of the industry — finding and drilling for oil and gas.
- UtilizationCommercial
- The share of a rig fleet that is under contract and working; a key demand signal.
W
- W-2 / 1099Roles
- Tax classifications distinguishing an employee (W-2, benefits, withholding) from an independent contractor (1099, no benefits, self-funds taxes).
- Walking rigEquipment
- A land rig that relocates itself across a pad on hydraulic walking feet.
- WellheadEquipment
- The surface equipment that supports the casing strings and seals the well.
- WorkoverDrilling
- Remedial work on an existing well to restore or improve production, such as replacing equipment or re-stimulating.
- Workover rigEquipment
- A smaller rig used to service, repair, or re-complete existing wells rather than drill new ones.
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