World rig register — land, offshore, intervention and specialist

Land rigs

Where most of the world's wells are drilled. Land rigs are classified by hook load and drawworks power, and increasingly by how fast they move between wells. On a pad campaign the rig move is a larger share of well cost than the drilling.

Class	Type	Typical rating	Where it works
Light	Truck-mounted / mobile	150–300 klb hook, 200–550 HP	Water wells, shallow gas, seismic, workover. Self-erecting, one or two loads.
Light	Single / carrier rig	250–400 klb hook, 400–650 HP	Shallow development, coalbed methane, workover. Drills single joints, no racking.
Medium	Double	500–750 klb hook, 750–1,000 HP	Conventional development to about 12,000 ft. Racks two-joint stands.
Heavy	Triple	750–1,500 klb hook, 1,000–2,000 HP	Deep development and exploration. Three-joint stands, the Gulf and North Africa workhorse.
Heavy	Fast-moving pad rig	750–1,500 klb hook, skidding or walking	Unconventional pad drilling. Walks between surface locations without rigging down.
Heavy	AC / VFD electric rig	1,500–3,000 HP, top drive, automated pipe handling	Long laterals, managed pressure, high torque. The current new-build standard.
Heavy	SCR electric rig	1,000–2,000 HP, DC drive	The prior generation, still the majority of the world's working heavy fleet.
Heavy	Mechanical rig	750–1,500 HP, chain or belt drive	Older fleets in Africa, Asia and the Middle East. Lower day rate, higher flat time.
Special	Slant rig	400–750 klb, mast inclined to 30–45°	Coastal, oil sands and SAGD. Reaches out from a small pad.
Special	Helirig	Modular, 100–250 klb	Jungle, mountain and roadless terrain. Every load flown in under a helicopter.
Special	Desert / dune rig	Heavy, wide-track substructure	Sand sea operations. Moves on its own mats, no prepared road.
Special	Arctic / winterised rig	Fully enclosed and heated	North Slope, Siberia, Arctic Canada. Ice road season dictates the campaign.
Special	Modular / containerised rig	Assembled from ISO-sized loads	Remote, island and border locations where transport is the constraint.
Special	Hydraulic / automated rig	Hydraulic mast, no traditional derrick	Small crew, geothermal and shallow work. Rapid rig-up.

Offshore mobile units

Classified by how they stay in place. A jackup stands on the seabed, a semi-submersible floats on submerged pontoons, a drillship floats on a hull. Water depth chooses the unit before anything else does.

Class	Type	Typical rating	Where it works
Bottom-founded	Jackup — independent leg cantilever	Up to ~400 ft water, 3 legs	The offshore workhorse. Cantilevers over a platform to drill and complete.
Bottom-founded	Jackup — mat-supported	Up to ~250 ft, soft seabed	Gulf of Mexico soft bottoms and river deltas.
Bottom-founded	Harsh-environment jackup	Up to ~500 ft, North Sea class	North Sea, Barents. Heavier legs, higher variable load, winterised.
Bottom-founded	Submersible / posted barge	Shallow water and swamp	Inland waters, Nigeria delta, Lake Maracaibo. Sinks onto the bottom.
Floating	Semi-submersible — moored	400–6,000 ft	Mid-water. Ballasted pontoons below the wave zone give low heave.
Floating	Semi-submersible — dynamically positioned	1,500–10,000 ft	Deepwater where mooring is impractical. Thrusters hold station.
Floating	Harsh-environment semi	Winterised, high transit	North Sea, Barents, offshore Canada. Designed for 100-year storm conditions.
Floating	Drillship — DP class 3	Up to 12,000 ft water, 40,000 ft drilling	Ultra-deepwater exploration. Highest variable deck load and transit speed.
Floating	Drillship — moored / converted	Shallower, benign	Older converted tankers, West Africa and Southeast Asia.
Floating	Ice-class drillship	Reinforced hull, disconnectable riser	Arctic and sub-Arctic. Can disconnect and move off station for ice.
Floating	Tender-assist rig	Barge or vessel alongside a platform	Southeast Asia and West Africa. Keeps the heavy equipment off the platform.
Floating	Drilling barge	Inland and swamp, under 20 ft	Louisiana marsh, Niger delta, Lake Maracaibo.

Fixed and production platform rigs

Permanently installed, or carried out to a platform and left there. These rigs drill the development wells and then stay for the field's working life, handling workovers and sidetracks.

Class	Type	Typical rating	Where it works
Fixed	Platform drilling rig	500–1,500 klb, permanently installed	Fixed steel jackets and concrete gravity structures. Drills the full well set from one location.
Fixed	Modular platform rig	Lifted out in modules and assembled	Smaller platforms and late-life infill. Removed when the campaign ends.
Fixed	Platform workover rig	150–500 klb	Lighter unit for interventions on an already drilled platform.
Floating production	TLP drilling rig	Tension leg platform, full drilling	Deepwater with dry trees. Riser tension governs the design.
Floating production	Spar drilling rig	Deep-draught cylindrical hull	Gulf of Mexico deepwater, dry tree wells.
Floating production	FPSO-mounted intervention	Vessel-based, riserless or light riser	Subsea field intervention without a separate rig.
Subsea	Subsea well access	Riser or riserless from a vessel	Intervening in subsea trees without a full drilling unit.

Intervention and workover units

More of these exist than drilling rigs. Most wells spend a few weeks being drilled and decades being intervened. Workover and intervention units are the larger fleet by number and the busier one by activity.

Class	Type	Typical rating	Where it works
Workover	Conventional workover rig	100–500 klb hook	Pulling and running tubing, pump changes, zone isolation. The most numerous rig class on earth.
Workover	Heavy workover / deep pulling unit	300–750 klb	Deep wells, heavy strings, fishing and recompletion.
Workover	Flush-by / pulling unit	Under 100 klb	Rod and pump service on shallow beam-pumped wells.
Live well	Hydraulic workover unit	Jacks, live well capable	Runs tubulars against pressure without killing the well.
Live well	Snubbing unit	Heaviest live-well method	Forces pipe into a well against pressure that would otherwise eject it.
Live well	Coiled tubing unit	Continuous pipe from a reel	Cleanouts, stimulation, milling, fishing. No connections to make.
Live well	Nitrogen / stimulation unit	Pumping only	Kick-off, cleanout and acid placement with no pipe in the hole.
Wireline	Slickline unit	Solid wire, mechanical	Gauge runs, plug setting, shifting sleeves. Fastest and cheapest intervention.
Wireline	Electric line unit	Conductor cable	Logging, perforating, setting bridge plugs and packers.
Wireline	Tractor-conveyed intervention	Electric line with downhole tractor	Horizontal and highly deviated wells where gravity will not convey tools.
Well service	Pressure pumping / frac spread	Multi-unit spread	Hydraulic fracturing and cementing. Not a rig, but rig-adjacent and rig-scheduled.
Well service	Plug and abandonment unit	Light rig or vessel	Permanent barrier placement and casing recovery at end of field life.

Specialist and non-oilfield rigs

The same crews and hydraulics, different industries. Mining, water, construction and research account for an enormous share of the world's drilling, and use the same tubulars, pumps and people.

Class	Type	Typical rating	Where it works
Mining	Diamond core rig — surface	Wireline core, NQ to PQ	Orebody definition. Core recovery is the performance measure.
Mining	Diamond core rig — underground	Compact, low headroom	Drilling from development drives inside a mine.
Mining	Reverse circulation rig	Dual-wall drill pipe	Fast chip sampling for grade control.
Mining	Blast hole drill	Track-mounted, large diameter	Open pit and quarry. Cycle time per hole is the economics.
Mining	Raise bore machine	Reams a shaft between levels	Ventilation and ore pass raises.
Mining	Shaft sinking rig	Vertical, very large diameter	New mine access shafts.
Water	Water well rig — rotary	Mud or air rotary	Municipal, agricultural and industrial supply.
Water	Water well rig — cable tool	Percussion	Older method, still used where formations are difficult and power is scarce.
Water	Dual rotary rig	Drills and cases simultaneously	Unconsolidated overburden and alluvium.
Civil	Horizontal directional drill rig	Pullback rated 20–1,200 klb	Pipeline, cable and utility crossings beneath rivers, roads and runways.
Civil	Piling rig	Auger, CFA or rotary	Building and bridge foundations.
Civil	Micro-tunnelling machine	Steered, remote	Sewer and utility installation at shallow depth.
Civil	Anchor and micropile rig	Small, high torque	Slope stabilisation and underpinning.
Geothermal	Geothermal rig — high temperature	1,000–2,000 HP, insulated	Hydrothermal and EGS wells. Temperature governs every component.
Geothermal	Ground source loop rig	Small rotary or sonic	Shallow closed loops for building heating.
Environmental	Sonic rig	Resonant vibration	Continuous undisturbed sampling in unconsolidated ground.
Environmental	Direct push rig	Hydraulic, no rotation	Shallow soil and groundwater sampling.
Research	Scientific ocean drilling vessel	Riserless and riser capable	JOIDES Resolution, Chikyu. Coring for research rather than production.
Research	Polar ice core drill	Electromechanical or thermal	Palaeoclimate records from ice sheets.
Research	Continental scientific drilling rig	Deep, coring	ICDP projects into fault zones, craters and volcanoes.

Rig classification and rating systems

How the industry compares one rig with another. A rig is described by what it can hoist, what it can circulate, what it can close in and how deep it is rated — not by a single number.

System	What it rates	Basis	Where it appears
Hook load rating	Maximum static load at the hook	API Spec 8C / 4F, in pounds or tonnes	The single most quoted rig number. Sets the heaviest casing string.
Drawworks power	Hoisting capability	Rated input horsepower	Often used as shorthand for rig class — 1,500 HP, 2,000 HP.
API Spec 4F	Mast and substructure	Certified capacity with and without racked pipe	Structural certificate. A rig can be power-adequate and fail on mast rating.
Rated drilling depth	Depth capability with a given pipe size	Manufacturer's rating by drill pipe weight	Marketing figure, but the basis of most rig-to-well matching.
BOP working pressure	Well control capability	API STD 53 — 5,000 / 10,000 / 15,000 psi	Set by maximum anticipated surface pressure, not by depth.
Mud pump power	Circulating capability	Hydraulic horsepower and maximum pressure	Governs hole cleaning and the feasibility of long laterals.
Top drive rating	Rotary torque and hoisting	Torque in ft-lb and load in tonnes	Limits extended reach and back-reaming capability.
Variable deck load	Offshore carrying capacity	Tonnes of consumables and tubulars	Governs offshore campaign length between resupply.
Water depth rating	Offshore station-keeping	Feet or metres, by unit class	The first filter for any offshore unit.
DP class	Dynamic positioning redundancy	IMO DP 1 / 2 / 3	Determines whether a unit may work over a live subsea well.
IADC rig classification	Common descriptive scheme	Type, power, depth	Used in day rate reporting and fleet statistics.
Winterisation class	Cold service capability	Design ambient temperature	Arctic, Barents and Siberian operations.

Land rigs

Class	Type	Typical rating	Where it works
Light	Truck-mounted / mobile	150–300 klb hook, 200–550 HP	Water wells, shallow gas, seismic, workover. Self-erecting, one or two loads.
Light	Single / carrier rig	250–400 klb hook, 400–650 HP	Shallow development, coalbed methane, workover. Drills single joints, no racking.
Medium	Double	500–750 klb hook, 750–1,000 HP	Conventional development to about 12,000 ft. Racks two-joint stands.
Heavy	Triple	750–1,500 klb hook, 1,000–2,000 HP	Deep development and exploration. Three-joint stands, the Gulf and North Africa workhorse.
Heavy	Fast-moving pad rig	750–1,500 klb hook, skidding or walking	Unconventional pad drilling. Walks between surface locations without rigging down.
Heavy	AC / VFD electric rig	1,500–3,000 HP, top drive, automated pipe handling	Long laterals, managed pressure, high torque. The current new-build standard.
Heavy	SCR electric rig	1,000–2,000 HP, DC drive	The prior generation, still the majority of the world's working heavy fleet.
Heavy	Mechanical rig	750–1,500 HP, chain or belt drive	Older fleets in Africa, Asia and the Middle East. Lower day rate, higher flat time.
Special	Slant rig	400–750 klb, mast inclined to 30–45°	Coastal, oil sands and SAGD. Reaches out from a small pad.
Special	Helirig	Modular, 100–250 klb	Jungle, mountain and roadless terrain. Every load flown in under a helicopter.
Special	Desert / dune rig	Heavy, wide-track substructure	Sand sea operations. Moves on its own mats, no prepared road.
Special	Arctic / winterised rig	Fully enclosed and heated	North Slope, Siberia, Arctic Canada. Ice road season dictates the campaign.
Special	Modular / containerised rig	Assembled from ISO-sized loads	Remote, island and border locations where transport is the constraint.
Special	Hydraulic / automated rig	Hydraulic mast, no traditional derrick	Small crew, geothermal and shallow work. Rapid rig-up.

Offshore mobile units

Class	Type	Typical rating	Where it works
Bottom-founded	Jackup — independent leg cantilever	Up to ~400 ft water, 3 legs	The offshore workhorse. Cantilevers over a platform to drill and complete.
Bottom-founded	Jackup — mat-supported	Up to ~250 ft, soft seabed	Gulf of Mexico soft bottoms and river deltas.
Bottom-founded	Harsh-environment jackup	Up to ~500 ft, North Sea class	North Sea, Barents. Heavier legs, higher variable load, winterised.
Bottom-founded	Submersible / posted barge	Shallow water and swamp	Inland waters, Nigeria delta, Lake Maracaibo. Sinks onto the bottom.
Floating	Semi-submersible — moored	400–6,000 ft	Mid-water. Ballasted pontoons below the wave zone give low heave.
Floating	Semi-submersible — dynamically positioned	1,500–10,000 ft	Deepwater where mooring is impractical. Thrusters hold station.
Floating	Harsh-environment semi	Winterised, high transit	North Sea, Barents, offshore Canada. Designed for 100-year storm conditions.
Floating	Drillship — DP class 3	Up to 12,000 ft water, 40,000 ft drilling	Ultra-deepwater exploration. Highest variable deck load and transit speed.
Floating	Drillship — moored / converted	Shallower, benign	Older converted tankers, West Africa and Southeast Asia.
Floating	Ice-class drillship	Reinforced hull, disconnectable riser	Arctic and sub-Arctic. Can disconnect and move off station for ice.
Floating	Tender-assist rig	Barge or vessel alongside a platform	Southeast Asia and West Africa. Keeps the heavy equipment off the platform.
Floating	Drilling barge	Inland and swamp, under 20 ft	Louisiana marsh, Niger delta, Lake Maracaibo.

Fixed and production platform rigs

Permanently installed, or carried out to a platform and left there. These rigs drill the development wells and then stay for the field's working life, handling workovers and sidetracks.

Class	Type	Typical rating	Where it works
Fixed	Platform drilling rig	500–1,500 klb, permanently installed	Fixed steel jackets and concrete gravity structures. Drills the full well set from one location.
Fixed	Modular platform rig	Lifted out in modules and assembled	Smaller platforms and late-life infill. Removed when the campaign ends.
Fixed	Platform workover rig	150–500 klb	Lighter unit for interventions on an already drilled platform.
Floating production	TLP drilling rig	Tension leg platform, full drilling	Deepwater with dry trees. Riser tension governs the design.
Floating production	Spar drilling rig	Deep-draught cylindrical hull	Gulf of Mexico deepwater, dry tree wells.
Floating production	FPSO-mounted intervention	Vessel-based, riserless or light riser	Subsea field intervention without a separate rig.
Subsea	Subsea well access	Riser or riserless from a vessel	Intervening in subsea trees without a full drilling unit.

Intervention and workover units

Class	Type	Typical rating	Where it works
Workover	Conventional workover rig	100–500 klb hook	Pulling and running tubing, pump changes, zone isolation. The most numerous rig class on earth.
Workover	Heavy workover / deep pulling unit	300–750 klb	Deep wells, heavy strings, fishing and recompletion.
Workover	Flush-by / pulling unit	Under 100 klb	Rod and pump service on shallow beam-pumped wells.
Live well	Hydraulic workover unit	Jacks, live well capable	Runs tubulars against pressure without killing the well.
Live well	Snubbing unit	Heaviest live-well method	Forces pipe into a well against pressure that would otherwise eject it.
Live well	Coiled tubing unit	Continuous pipe from a reel	Cleanouts, stimulation, milling, fishing. No connections to make.
Live well	Nitrogen / stimulation unit	Pumping only	Kick-off, cleanout and acid placement with no pipe in the hole.
Wireline	Slickline unit	Solid wire, mechanical	Gauge runs, plug setting, shifting sleeves. Fastest and cheapest intervention.
Wireline	Electric line unit	Conductor cable	Logging, perforating, setting bridge plugs and packers.
Wireline	Tractor-conveyed intervention	Electric line with downhole tractor	Horizontal and highly deviated wells where gravity will not convey tools.
Well service	Pressure pumping / frac spread	Multi-unit spread	Hydraulic fracturing and cementing. Not a rig, but rig-adjacent and rig-scheduled.
Well service	Plug and abandonment unit	Light rig or vessel	Permanent barrier placement and casing recovery at end of field life.

Specialist and non-oilfield rigs

The same crews and hydraulics, different industries. Mining, water, construction and research account for an enormous share of the world's drilling, and use the same tubulars, pumps and people.

Class	Type	Typical rating	Where it works
Mining	Diamond core rig — surface	Wireline core, NQ to PQ	Orebody definition. Core recovery is the performance measure.
Mining	Diamond core rig — underground	Compact, low headroom	Drilling from development drives inside a mine.
Mining	Reverse circulation rig	Dual-wall drill pipe	Fast chip sampling for grade control.
Mining	Blast hole drill	Track-mounted, large diameter	Open pit and quarry. Cycle time per hole is the economics.
Mining	Raise bore machine	Reams a shaft between levels	Ventilation and ore pass raises.
Mining	Shaft sinking rig	Vertical, very large diameter	New mine access shafts.
Water	Water well rig — rotary	Mud or air rotary	Municipal, agricultural and industrial supply.
Water	Water well rig — cable tool	Percussion	Older method, still used where formations are difficult and power is scarce.
Water	Dual rotary rig	Drills and cases simultaneously	Unconsolidated overburden and alluvium.
Civil	Horizontal directional drill rig	Pullback rated 20–1,200 klb	Pipeline, cable and utility crossings beneath rivers, roads and runways.
Civil	Piling rig	Auger, CFA or rotary	Building and bridge foundations.
Civil	Micro-tunnelling machine	Steered, remote	Sewer and utility installation at shallow depth.
Civil	Anchor and micropile rig	Small, high torque	Slope stabilisation and underpinning.
Geothermal	Geothermal rig — high temperature	1,000–2,000 HP, insulated	Hydrothermal and EGS wells. Temperature governs every component.
Geothermal	Ground source loop rig	Small rotary or sonic	Shallow closed loops for building heating.
Environmental	Sonic rig	Resonant vibration	Continuous undisturbed sampling in unconsolidated ground.
Environmental	Direct push rig	Hydraulic, no rotation	Shallow soil and groundwater sampling.
Research	Scientific ocean drilling vessel	Riserless and riser capable	JOIDES Resolution, Chikyu. Coring for research rather than production.
Research	Polar ice core drill	Electromechanical or thermal	Palaeoclimate records from ice sheets.
Research	Continental scientific drilling rig	Deep, coring	ICDP projects into fault zones, craters and volcanoes.

Rig classification and rating systems

How the industry compares one rig with another. A rig is described by what it can hoist, what it can circulate, what it can close in and how deep it is rated — not by a single number.

System	What it rates	Basis	Where it appears
Hook load rating	Maximum static load at the hook	API Spec 8C / 4F, in pounds or tonnes	The single most quoted rig number. Sets the heaviest casing string.
Drawworks power	Hoisting capability	Rated input horsepower	Often used as shorthand for rig class — 1,500 HP, 2,000 HP.
API Spec 4F	Mast and substructure	Certified capacity with and without racked pipe	Structural certificate. A rig can be power-adequate and fail on mast rating.
Rated drilling depth	Depth capability with a given pipe size	Manufacturer's rating by drill pipe weight	Marketing figure, but the basis of most rig-to-well matching.
BOP working pressure	Well control capability	API STD 53 — 5,000 / 10,000 / 15,000 psi	Set by maximum anticipated surface pressure, not by depth.
Mud pump power	Circulating capability	Hydraulic horsepower and maximum pressure	Governs hole cleaning and the feasibility of long laterals.
Top drive rating	Rotary torque and hoisting	Torque in ft-lb and load in tonnes	Limits extended reach and back-reaming capability.
Variable deck load	Offshore carrying capacity	Tonnes of consumables and tubulars	Governs offshore campaign length between resupply.
Water depth rating	Offshore station-keeping	Feet or metres, by unit class	The first filter for any offshore unit.
DP class	Dynamic positioning redundancy	IMO DP 1 / 2 / 3	Determines whether a unit may work over a live subsea well.
IADC rig classification	Common descriptive scheme	Type, power, depth	Used in day rate reporting and fleet statistics.
Winterisation class	Cold service capability	Design ambient temperature	Arctic, Barents and Siberian operations.

EVERY RIG THAT DRILLS,AND WHAT DECIDES ITS CLASS.

Land rigs

Offshore mobile units

Fixed and production platform rigs

Intervention and workover units

Specialist and non-oilfield rigs

Rig classification and rating systems

Land rigs

Offshore mobile units

Fixed and production platform rigs

Intervention and workover units

Specialist and non-oilfield rigs

Rig classification and rating systems

EVERY RIG THAT DRILLS,
AND WHAT DECIDES ITS CLASS.