Extended Operational and Trade Vocabulary

Offshore Oil and Gas Marine Operations glossary

The marine operations supporting offshore oil and gas: anchor-handling and supply vessels (AHTS, AHV), accommodation flotels, active heave compensation for subsea lifts, air gap clearance, and the station-keeping and lifting systems that serve MODUs and floating production units. Grounds each term in the offshore field operation it supports.

275 defined terms.

Showing 250 on this page (page 1 of 2).

A

Accommodation Flotel: Semi-submersible or monohull vessel providing offshore beds, often with gangway.
Active Heave Compensation: Crane/winch system that counters vessel heave in real time using hydraulics.
AHTS: Anchor Handling Tug Supply, multipurpose vessel for salvage tow, anchor work, and supply.
AHV: Anchor handling vessel without supply role; pure towage and anchor work.
Air gap: Vertical distance from the fuel surface to the top of the tank, used in ullage measurement.
Alexander L. Kielland: Norwegian flotel that capsized 1980 in Ekofisk; 123 fatalities; brace fatigue failure.
Alpha Line: Primary mooring or hawser leg in a SPM arrangement.
Anchor Chaser: Grapnel-like device dragged to recover lost anchor pendant wires.
Anchor Handling Winch: Heavy double-drum winch on AHTS for chain/wire deployment.
Anchor Pattern: Geometric layout of mooring legs around a moored unit.
API RP 17: API series covering subsea production systems including trees, manifolds, risers.
API RP 2A: American Petroleum Institute recommended practice for fixed offshore platform design.
API RP 2SK: API recommended practice for design and analysis of stationkeeping for floating structures.
ASOG: Activity Specific Operating Guidelines used by DP operators per IMCA M220.
AUV: Autonomous Underwater Vehicle.
Auxiliary Winch: Smaller winch on AHTS used for tugger work and anchor pendant handling.

B

Backload: Cargo returned from offshore installation to shore on a PSV.
Ballast Control Room: Manned space on semi-submersibles managing column flooding.
Bare Boat Charter: Vessel hire without crew; charterer assumes operational control.
Bell Diving: Saturation diving deployment from a closed bell on a DSV.
Berth Box: Defined sea area assigned for a vessel in a DP field operation.
Blowout: Uncontrolled release of formation fluids from a well.
BOEM: US Bureau of Ocean Energy Management; offshore leasing and resource evaluation.
BOP: Blowout preventer; stack of rams and annulars sealing the wellhead in emergencies.
Bop Control Pod: Subsea hydraulic/electrical pod operating BOP functions; usually blue and yellow redundant.
BOP Test Stump: Surface fixture for pressure testing BOP components.
BOSIET: Basic Offshore Safety Induction and Emergency Training; OPITO standard.
Bow Loading System: Tanker bow connection for offtake from FPSO/FSO.
BPM: Barrels per minute, stimulation pumping rate.
Bridle: Two-leg rope or chain attached to a single point.
Brownfield: Existing producing offshore field undergoing modification.
BSEE: US Bureau of Safety and Environmental Enforcement; offshore safety regulator post-Macondo.
Bullnose: Towing notch at the AHTS stern aiding wire alignment.
Bundle: Pipe-in-pipe assembly towed to field for subsea installation.
Buoyancy Tank: Submerged tank giving lift to risers, tow strings, or moorings.

C

CALM Buoy: Catenary anchor leg mooring; surface buoy held by catenary chain legs for tanker offtake.
Cantilever: Drilling structure on jack-ups slid out over a platform to drill multiple wells.
Capping Stack: Subsea device installed over a blown-out well to seal it; post-Macondo industry response.
Carousel: Rotating storage table on cable/umbilical lay vessels.
Cathodic Protection: Sacrificial or impressed current system protecting subsea steel from corrosion.
CFD: Computational fluid dynamics used for offshore structure hydrodynamic loading.
Choke and Kill Lines: High pressure lines on the BOP riser for well control.
Christmas Tree: Stack of valves on a wellhead controlling production flow; subsea or surface (XT).
Clump Weight: Hanging weight on mooring or riser to depress catenary shape.
Coflexip: Brand-origin term for flexible bonded pipe; now TechnipFMC.
Compensated Cargo Handling: Heave-compensated crane lifts to fixed structures.
Completion: Sequence preparing a drilled well for production with tubing and tree.
Conductor: Outermost large diameter casing driven into seabed.
Construction Support Vessel: General term for CSV; subsea installation/IRM duties.
CTV: Crew transfer vessel; small catamaran transferring wind technicians.
Cursor Frame: Guide structure on drillships transporting BOP between moonpool and seabed.
Cyscan: Marine Technologies/Guidance Marine laser DP reference system.

D

DARPS: Differential Absolute and Relative Positioning System; DP reference for FPSO offtake.
Davit: Curved crane for hoisting and lowering boats and stores.
Decommissioning: End-of-life removal or making safe of offshore facilities.
Deepwater Horizon: Transocean semi-submersible lost 2010 at Macondo; 11 fatalities; largest US marine oil spill.
Derrick: Cargo boom rigged to a mast.
Diverless Connection: Subsea connection methods using ROV interfaces below diver depth.
Diverter: Low pressure flow diversion system above the BOP on a riser.
Diving Bell: Pressurised chamber for transferring saturation divers to underwater work sites.
DNV: Det Norske Veritas (DNV); IACS member classification society.
DP1: Dynamic positioning class with no redundancy; loss of one element can cause position loss.
DP2: Dynamic positioning class tolerant to any single fault excluding loss of compartment.
DP3: DP class tolerant to any single fault including fire or flood in one compartment.
Drag Embedment Anchor: Traditional fluke anchor embedding by horizontal pull.
Drape Line: Catenary section of a steel catenary riser at touchdown.
Drill Floor: Working deck around the rotary table.
Drilling Riser: Large diameter marine riser connecting subsea BOP to floating rig.
Drillship: Mobile offshore drilling unit shaped as a ship.
Dropped Object: Item falling from height offshore; major safety category (DROPS).
DSV: Dive Support Vessel, dynamically positioned platform for saturation diving operations.
Dynamic Positioning: Computer-controlled thruster station keeping for salvage and dive vessels.

E

Ekofisk: First major Norwegian North Sea field; Phillips Petroleum, on-stream 1971.
Emergency Disconnect Sequence (EDS): Programmed sequence to safely disconnect LMRP from BOP.
Emergency Quick Disconnect: Rapid disconnect on turret moorings allowing FPSO to leave field.
EPC: Engineering, procurement, construction contract structure.
EPCI: EPC plus installation; common offshore contract type.
ERRV: Emergency response and rescue vessel; standby duties in UK sector.
ESDV: Emergency shutdown valve in process trains.
Export Riser: Riser carrying produced hydrocarbons from platform to pipeline or tanker.
External Turret: Turret mooring mounted on an outboard structure forward of the FPSO bow.

F

Fanbeam: MDL laser-based DP position reference system.
Fast Supply Vessel (FSV): High speed crew/cargo vessel, common Gulf of Mexico.
FEED: Front end engineering design phase preceding EPC.
FiFi: Fire-fighting capability classification one, two, or three for salvage and support tugs.
Fixed Platform: Bottom-founded steel jacket or concrete structure pile-fixed to seabed.
Flare Tower: Structure supporting gas flare boom on offshore platform.
Flexible Riser: Unbonded or bonded flexible pipe used as dynamic riser.
Flexjoint: Elastomeric riser joint allowing angular rotation.
FLNG: Floating liquefied natural gas facility; liquefaction and storage at sea.
Flotel: Floating accommodation unit, see Accommodation Flotel.
Flowline: Subsea pipeline from wellhead to manifold or facility.
FMEA: Failure modes and effects analysis; mandatory for DP2/DP3 vessels.
FOET: Further Offshore Emergency Training; OPITO BOSIET refresher.
FPSO: Floating production, storage and offloading unit; turret or spread moored.
FPU: Floating production unit without storage.
FSO: Floating storage and offloading unit, no processing.
FSRU: Floating storage and regasification unit for LNG import.
FSU: Floating storage unit; tanker hull used for storage only.
Fugro Seastar: Long-standing DGNSS augmentation service used as DP reference.

G

Gangway System: Motion-compensated walkway for W2W transfers (e.g., Ampelmann, Uptime).
GBS: Gravity-based structure; concrete platform held by self-weight on seabed.
Gimbal: Pivot supporting jack-up leg-to-hull connection or crane base.
Girassol: Deepwater Angolan field (Total) using FPSO and buoyancy can risers.
GNSS: Global navigation satellite system; GPS, GLONASS, Galileo, BeiDou.
GoM: Gulf of Mexico offshore region.
Goose neck: Vent terminal shape for tanks.
GWO: Global Wind Organisation; sets BST and BTT wind training standards.
Gyro Compass: North-seeking compass based on gyroscopic precession.

H

Halfen Channel: Cast-in anchor channel used for offshore equipment fixing.
Hang-off: Temporary stowage of riser or drillstring on rig.
Heave Compensator: System absorbing vessel heave between vessel and load.
Helideck: Flight deck on surface combatant sized for embarked helicopter.
Hook Load: Weight suspended from the drilling hook.
HPHT: High pressure high temperature wells; specialized BOP and tree requirements.
HSE: UK Health and Safety Executive; offshore safety regulator UKCS.
Hub: Major transhipment port served by multiple feeder services.
Hydrate: Solid ice-like compound of gas and water; flow assurance hazard.

I

IADC: International Association of Drilling Contractors; daily drilling report standard.
IMCA: International Marine Contractors Association; DP, diving, ROV guidance.
IMCA M103: Common DP class requirements guidance document.
IMCA M117: Training and experience of key DP personnel.
IMCA M220: Operational activity planning for DP vessels (ASOG, CAM, TAM).
IMR: Inspection, maintenance and repair scope for subsea field life.
IMU: Inertial measurement unit for motion sensing on DP and survey.
In-line Tee: Subsea tee for tying flowlines into a main pipeline.
Inertial Aided Positioning: Combined INS and acoustic positioning for subsea reference.
Installation Aid: Equipment used during subsea hardware deployment.
Insulated Pipe-in-pipe: Subsea pipeline configuration for thermal insulation.
Internal Turret: Turret mooring located within the FPSO hull, allowing weathervaning.
IRM: Inspection, repair and maintenance work, often via ROV.
ISO 19901: Series of ISO standards for offshore structures.

J

Jack-Up Rig: MODU with retractable legs deployed to seabed.
Jacket: Outer protective casing on a tank container.
Jacking System: Strand jacks used for parbuckling and lifting heavy wreck sections.
Joint Industry Project (JIP): Collaborative project on shared technical challenges.
Jones Act: US cabotage law restricting domestic offshore trades to US vessels.
JU2000E: Friede & Goldman jack-up design class widely operated.
Jumper: Short subsea pipe spool between tree and manifold or PLET.

K

K-Pos: Kongsberg DP system family; common on offshore vessels.
Kick: Unscheduled influx of formation fluids into the wellbore.
Kill Line: BOP line for pumping kill fluid into the well.
Kingpost: Pedestal for cranes or davits.
Knuckle Boom Crane: Articulating crane common on PSVs and CSVs.

L

LARS: Launch and recovery system for ROVs, bells, and AUVs.
Lay Tower: Vertical pipelay tower on rigid reel and J-lay vessels.
Layback: Horizontal distance between vessel and pipeline touchdown.
Leave In Place: Decommissioning option leaving subsea structures in situ.
LMRP: Lower marine riser package; disconnectable upper section of subsea BOP stack.
Logistic Vessel: General supply unit, see PSV.
LOTOTO: Lock out, tag out, try out; isolation safety practice.
Lower Stack: Lower section of subsea BOP, contains the rams and wellhead connector.

M

MAERSK Drilling: Major offshore drilling contractor, now part of Noble Corporation.
Manifold: Pipe assembly at the ship side where bunker hoses connect.
Marine Operations Manual (MOM): Vessel-specific manual for DP and field operations.
MARPOL: International Convention for the Prevention of Pollution from Ships, 1973, as modified by the 1978 and 1997 Protocols; the IMO treaty governing marine pollution across six annexes.
MEG: Monoethylene glycol; hydrate inhibitor injected into subsea flowlines.
Methanol Injection: Alternative hydrate inhibitor.
Mid-water Arch: Arched support imparting wave-shape to flexible risers.
MODU: Mobile offshore drilling unit; jack-up, semi-submersible or drillship.
MODU Code: IMO code for mobile offshore drilling units.
Moonpool: Vertical opening through a vessel hull for through-hull operations.
Mooring buoy: Buoy to which a ship may secure.
MOPU: Mobile offshore production unit, often ex-MODU.
MPSV: Multipurpose support vessel; subsea, ROV, light construction.
Mud: Drilling fluid circulated through the wellbore.
MUX Cable: Multiplex umbilical operating BOP control pods.

N

NCS: Norwegian Continental Shelf.
Nitrox: Oxygen-enriched diving gas mix.
Noble Corporation: Major offshore drilling contractor.
NORSOK: Norwegian standards for the petroleum industry (e.g., NORSOK N-001, D-010).
North Sea: Shelf sea between Britain and continental Europe.
NPD: Norwegian Petroleum Directorate (now Sokkeldirektoratet).

O

Ocean Ranger: ODECO semi-submersible lost off Newfoundland 1982; 84 fatalities.
OCIMF: Oil Companies International Marine Forum, owner of SIRE.
OCV: Offshore construction vessel; heavy crane and subsea install capability.
OEUK: Offshore Energies UK; trade body (formerly Oil and Gas UK).
OIM: Offshore Installation Manager; person in charge on offshore unit.
OPITO: Offshore safety training accreditation body (BOSIET, MIST, HUET).
OPRC: Oil Pollution Preparedness, Response and Co-operation convention (IMO 1990).
OSV: Offshore support vessel; umbrella term for AHTS, PSV, MPSV, etc.
Overpull: Tension exceeding nominal load applied to anchor lines or pipelines.

P

P-36: Petrobras semi-submersible lost 2001 off Brazil; 11 fatalities; gas explosion.
Pad Eye: Welded plate with hole forming a lashing point.
Pancake Connector: Subsea horizontal hub connector type.
Passive Heave Compensation: Gas-spring or counterweight heave compensation without active control.
Pendant Wire: Short wire between anchor and surface buoy or workboat.
Permanent Mooring: Long term mooring sized for design return period storms.
PFEER: UK Prevention of Fire and Explosion, and Emergency Response Regulations 1995.
Pile Driving: Hammering tubular piles into seabed for foundations.
Pipelay Vessel: Specialist S-lay, J-lay or reel-lay construction vessel.
Piper Alpha: Occidental UK platform lost 1988; 167 fatalities; led to Cullen Inquiry.
PLEM: Pipeline end manifold.
PLET: Pipeline end termination; subsea structure terminating a pipeline.
Plug and Abandon (P&A): Sealing a well permanently with cement plugs.
Polyester Mooring: Synthetic taut-leg mooring with polyester rope segments.
POOH: Pull out of hole; tripping pipe from wellbore.
POSMOOR: Kongsberg position mooring control system for moored rigs.
PRS: Polski Rejestr Statkow, Polish Register of Shipping, IACS member.
PSA: Petroleum Safety Authority Norway.
PSV: Platform supply vessel; cargo deck plus mud/brine/methanol tanks.
Pull-in: Operation pulling a flowline or umbilical into a platform J-tube.

Q

Q4000: Helix multi-service vessel used at Macondo.
Quick Connect/Disconnect: Hydraulic clamp connector for riser/mooring.

R

Radascan: Guidance Marine microwave DP reference using transponders.
RADius: Kongsberg microwave DP reference.
Ram BOP: BOP cavity with closing rams (blind, shear, pipe, variable).
Reel-lay: Pipeline installation from a vertical reel onto seabed.
Renewables Support Vessel: Vessel serving offshore wind; SOV, CTV, WTIV.
Riser: Conduit from seabed to surface; drilling, production, export, or workover.
Riser Tensioner: Compensator maintaining tension on drilling riser.
ROV: Remotely Operated Vehicle used for survey, hot tap support, and deep salvage work.
ROVSV: ROV support vessel.

S

SALM: Single anchor leg mooring; rigid riser column moored to single seabed anchor.
Saturation Diving: Long-duration deep diving with divers held at depth pressure.
SCM: Subsea control module; electrohydraulic module on tree/manifold.
SCR: SAR Cooperation Plan required under SOLAS Chapter V Regulation 7.3 for passenger ships.
Sea Fastening: Heavy welded structure securing project cargo for ocean voyage.
SEACON: Common subsea electrical wet-mate connector brand.
Semi-submersible: Column-stabilized floating rig with submerged pontoons.
Shuttle Tanker: DP tanker exporting FPSO crude to shore.
SIMOPS: Simultaneous operations on or near an installation.
SOLAS: International Convention for the Safety of Life at Sea, 1974; the IMO treaty setting minimum construction, equipment, and operation standards for merchant ships.
SOV: Service operation vessel for offshore wind; DP2, walk-to-work, ~60 m+.
SPAR: Deep-draft vertical cylindrical floater (classic, truss, cell).
SPM: Single point mooring offshore terminal.
Spool: Short pipe section connecting subsea structures.
Spread mooring: Multi-line mooring pattern for moored offshore units.
SSIV: Subsea isolation valve.
Stab and Hinge: Connection method for jumpers and spools.
Standby Vessel: UK ERRV in proximity of installation.
Stinger: Curved overboard ramp on S-lay pipelay vessels.
Subsea Tree: Christmas tree installed on the seabed.
Suction Pile/Anchor (SCA): Inverted cylindrical pile installed by differential suction.
Surf: Subsea umbilicals, risers and flowlines; project category.

T

TAM: Task Appropriate Mode in IMCA M220 DP framework.
Telescopic Joint: Slip joint on drilling riser accommodating vessel heave.
Tension Leg Platform (TLP): Vertically moored compliant platform held by tendons.
Tensioner: Hydraulic system applying tension to drilling riser or pipe.
Test Tree: Subsea test tree for well testing operations.
Thrusters: Azimuth or tunnel propellers used in DP stationkeeping.
TLP Tendons: Vertical tubular mooring members under tension.
Top Tensioned Riser: Vertical riser kept in tension by surface tensioners.
Topside: Side of the hull above the waterline.
Torpedo Anchor: Free-fall finned penetrator anchor used by Petrobras.
Tow Master: Person in charge during rig moves and ocean tows.
Transocean: Major offshore drilling contractor; owned Deepwater Horizon.
Tree Cap: Cap protecting subsea tree during suspended periods.
Tugger Winch: Small auxiliary winch for handling lines on deck.
Turret Mooring: Turret allowing FPSO to weathervane around fixed seabed legs.