GLOSSARY: OFFSHORE ENGINEERING TERMS

OFFSHORE ENGINEERING GLOSSARY TERMS

 

Accumulator: A pressure vessel charged with nitrogen gas and used to store hydraulic fluid under pressure for the operation of hydraulic valve actuators.

 

Actuator: A mechanical device or the remote or automatic operation of a valve or choke.

 

Annulus: Space between concentric casing strings.

 

Associated gas:  Naturally occurring reservoir gas found in association with oil, either dissolved in the oil or found as a cap or pocket of free gas above the oil.

 

Azimuthing thruster: Rotatable ducted propeller used in conjunction with a dynamic positioning system to enable ships to maintain position without the use of anchors.

 

Blowout: Uncontrolled release of well fluids from the well bore during drilling operations.

 

Bell Nipple: Receptacle attached to the top of the blowout preventer or marine drilling riser which directs the drilling mud returns to the shale shaker or mud pits.

 

BOP: Device attached to the casing head during drilling operations that allows the well to be sealed to confine the well fluids in the well bore.

 

Brownfield: An existing onshore or offshore facility, e.g. 'brownfield modification' is an upgrade to an existing facility.

Bubble point: Point at which dissolved gasses begin to vaporize from liquid. Dependent on temperature, pressure and gas/liquid composition.

 

Caisson: Length of pipe extending vertically downwards from an installation into the sea as a means of disposing of waste waters, or for the location of a sea water pump.

 

Casing: Pipe used to line and seal the well and prevent collapse off the borehole. A number of casing strings (Lengths) are used in ever decreasing diameters.

 

Cathodic protection: Corrosion protection system which relies on sacrificial anodes or impressed current to protect submerged steel components from corrosion by electrolytic action.

 

Clean Fuel: Fuel that has been modified such that, on combustion, it produces lower emissions.

Condensate: Volatile liquid consisting of the heavier hydrocarbon factions that condense out of the gas as it leaves the well, a mixture of pentanes and higher hydrocarbons.

 

Conductor: The first and largest diameter pipe to be inserted (spudded) into the seabed when drilling a well. It keeps the hole open, provides a return passage for the drilling mud and supports the subsequent casing strings.

 

Choke: A valve like device with a fixed or variable aperture specifically intended to regulate the flow of fluids.

 

Christmas tree: An assembly of valves attached to the wellhead and used to control well production.

 

Crossover: Item used to connect one component to another differing in size, thread type or pressure rating.

 

Debottlenecking: The process of increasing the production capacity of existing facilities through the modification of existing equipment to remove throughput restrictions.

Decommissioning:  The process for removal of a plant or piece of equipment from an operational state.

Dew point: Temperature at which liquids condense from a gas.

 

Downstream - The processing, refining and distribution of oil & gas.

Duster: Dry well drilled during exploration.

 

Dynamic positioning: Satellite monitoring system used to control the action of thruster propellers to maintain a vessel on location without deploying anchor.

 

Emergency shutdown valve (ESDV): An automatically operated normally open valve used for

Isolating a subsea pipeline.

 

Enhanced oil recovery: Means used to assist in the extraction of oil either by installing equipment into the production tubing or by injecting water or gas into the reservoir.

 

Front End Engineering Design (FEED):The stage of design between concept evaluation and detailed design during which the chosen concept is developed such that most key decisions can be taken. Output of FEED includes estimate of total installed cost and schedule.

Fire loop: A pneumatic control line containing temperature sensing elements (fusible plugs, synthetic tubing, etc.)  which, when activated, will initiate a platform shutdown.

 

Fiscal metering: The measurement of oil, gas or condensate flow rate for taxation purposes.

 

Flare stack: Elevated tower containing a pipe used for the discharge and burning of waste gases.

 

Flash drum: Pressure vessel used to lower the pressure of oils and other liquids involved with the production process in order to encourage the vaporization of dissolved gases.

 

Flowline: Piping which directs well fluids from wellheads to manifold or first process vessel.

 

Fluid: A generic term meaning a gas, vapor, liquid or combinations thereof.

 

Floating Production, Storage and Offloading Vessel (FPSO): A floating tank system designed to receive oil or gas produced from a nearby platform, process it, and store it until the oil or gas can be offloaded, or sent through a pipeline. They are typically used in deeper waters and often in conjunction with subsea facilities.

Grout: Mixture of cement and water (no sand) used to secure and seal attachments such as piles into jacket legs.

 

Greenfield: A new field development requiring new facilities, either onshore or offshore.

Header: That part of a manifold which directs fluid to a specific process system.

 

Hydrate: Solid, ice like compound consisting of molecules of water and hydrocarbon gasses.

 

Hydrocylone: Separation device utilizing centrifuging principles to remove oils from water, or as a multiclycone to remove liquids and, solids from a gas stream.

 

Heat affected zone (HAZ): That portion of the base metal which has not been melted, but whose mechanical properties or microstructure have been affected by the heat generated during the welding process.

 

Intrinsically safe: Electrical equipment which is incapable of igniting a flammable gas mixture or combustible materials.

 

Installation: May be fixed or mobile and used directly or indirectly for the exploration or production of mineral resources.

 

Installation, fixed: A fixed offshore Structure involved in the production of oil or gas which may be constructed of steel or concrete.

 

Jacket: Steel support framework used to support platform topsides.

 

J-T valve: Throttle valve used to reduce the pressure and temperature of a gas stream, associated, with the NGL removal process.

 

Knock out: Removal of liquids from a gas stream within a pressure vessel.

 

Lower explosive limit (LEL): The lowest concentration by volume of combustible gases in mixture with air that can be ignited at ambient temperature conditions.

 

LNG: Liquefied natural gas, gaseous at ambient temperatures and pressures but held in the liquid state by very low temperatures to facilitate storage and transportation in insulated vessels.

 

LNG Regasification - The process where LNG is reheated and turned into gas.

LPG: Liquefied petroleum gas, essentially propane and butane held in the liquid state under pressure to facilitate storage and transportation.

 

Manifold: An assembly of pipes, valves and fittings by which fluid from one or more sources is

selectively directed to various process systems.

 

Marine drilling riser: Pipe extending from the blowout preventer on the seabed to the drilling rig on the surface, to permit the return of the drilling mud.

 

Microwave: High frequency muIti-channel radio communications system designed to carry information between two points linked by line of sight transmission.

 

Midstream: Industry activities that fall between exploration & production (upstream) and refining & marketing (downstream). Usually refers to the storage and transportation of oil & gas, but in some cases describes the further processing of oil & gas from upstream processing facilities to allow for storage and transportation (see LNG).

Mobile installation: One which can be moved from place to place without major dismantling or modification.

 

Module: Self-contained liftable package forming part of the topside facilities of an offshore installation. E.g. accommodation module, compressor module, drilling module etc..

 

Multiphase: Practice of flowing unsterilized well fluids (oil with high gas content) in a single pipeline by boosting the pressure to prevent vaporization of the dissolved gasses.

 

Natural gas: Hydrocarbon gas occurring naturally from underground reservoirs both on and offshore.

 

NGL: Natural gas liquids, a mixture of hydrocarbon liquids which include butane and ethane obtained from natural gas. May be produced from condensate reservoirs but more probably produced as a byproduct of oil production.

 

Nipple: A section of threaded or socket welded pipe used as an appurtenance that is less than 12 inches in length. Often used to describe any short length of open ended pipe.

 

Nozzle: Flanged inlet or outlet connection on a pressure vessel.

 

Mudline: Seabed.

 

Packer: Device for sealing one casing string from another, or from the production tubing.

 

Pedestal: Large diameter, vertical tube or tub onto which a crane is attached.

 

Photogrammetric: The use of still 'photography to capture dimensional information for transposing into drawings.

 

Pig: Spherical device inserted in to a gas subsea pipeline to sweep the line of deposits of rust, scale and condensed liquids. May also be used to clean oil pipelines of wax and may be "intelligent", that is containing measuring and inspection equipment.

 

Pig trap: A pressure chamber permitting the entry or removal of equipment into the subsea pipeline, normally pigs.

 

Pipeline: Piping used to convey fluids between platforms or between a platform and a shore facility.

 

Pipe spool: Single length of pipe with flanged ends.

 

Platform, offshore: A fixed offshore structure involved in the production of oil or gas which may be constructed of steel or concrete. Term used frequently to describe an offshore installation.

 

Pressure vessel: Container, normally cylindrical used to contain internal or occasionally external pressure.

 

Produced water: Formation water removed from the oil and gas in the process pressure vessels.

 

Production separator: Main process vessel used primarily for the separation of gas, oil (and

condensate) and water.

 

Production tubing: Pipe used in wells to conduct fluid from the producing formation into the Christmas tree. Unlike the casing the tubing is designed to be replaced during the life of the well, if required.

 

Purge: Maintain gas flow in an over rich, or lean concentration so as to avoid the buildup of oxygen and an explosive mixture.

 

Quality assurance: A sequence of planned and systematic actions necessary to provide adequate confidence that a product or service will satisfy given requirements of quality.

 

Quality control: The operational techniques and activities that are used to ensure that a quality product or service will be produced.

Rig: A term normally associated with drilling equipment, that is to say a drilling rig. Also a slang term used extensively to describe any of the structures and vessels associated with oil and gas exploration and production.

Riser: The vertical portion of a subsea pipeline (including the bottom bend) arriving on or departing from a platform.

Rock dumping: Deposition of rocks onto subsea pipelines to provide protection against anchors and fisherman’s nets when burying the pipe is impractical. Rocks and gravel may also be dumped around subsea wellheads and jacket legs to repair scour damage.

Seismic survey: The use of artificially generated sound waves to determine the type of rock formations below the ground or under the sea bed by monitoring the reflected sound wave signals.

Scour: Removal of the seabed in the vicinity of a jacket, subsea wellhead or pipeline by tidal action.

Scrubber: Pressure vessel containing equipment designed to remove or scrub liquids from a gas stream.

Shuttle tanker: Moderate-sized oil tanker used to transport oil from larger vessels into port.

Skid: Steel framework used to contain equipment, may be transportable.

Stress corrosion cracking: The cracking which results from a combination of stress and corrosion.

Slew ring bearing: Large ball or roller bearing which connects crane to pedestal and permits rotation.

Slug: An accumulation of water (may also be sand or condensate) in a gas pipeline.

Spudding: A term used to describe the insertion of the conductor into the seabed when drilling a well. May also be used to describe the process of setting the legs of a jack-up into the seabed.

Stinger: Tubular steel support frame attached to the stem of a pipelay barge to control the bending of the pipe as it enters the water.

Stripping: The removal or replacement of drill pipe or tubing strings from a well under pressure using a stripping BOP.

Stripping Gas – Gas, normally process gas used to assist in the purification of a liquid by reducing the partial pressure of gaseous contaminants to encourage vaporization.

Swabbing: The lowering of the hydrostatic pressure in the hole due to the upward movement of the drill pipe and/or tools. Also the use of wireline equipment to clean a well by scooping out liquids.

Sulphide stress cracking: Cracking of metallic materials due to exposure to fluids containing hydrogen sulphide.

Subsea Tiebacks: A method of connecting new discoveries to existing production facilities, improving the economics of offshore oil & gas production.

Telemetry:  System for the collection, collation and transformation to a remote source using radio, satellite, fiber optics or cable links. Also associated with the remote control of process equipment.

 

Throttle: Regulation of fluid flow by a throttling valve or fixed orifice.

 

Topsides: Upper part of a fixed installation which sits on top of the jacket and consists of the decks, accommodation and process equipment.

 

Upstream: The development and production of oil and gas.

Vent: A pipe or fitting on a vessel that can be opened to the atmosphere.

 

Vent stack: Open ended pipe and support framework used to discharge vapours into the atmosphere at a safe location above the installation without combustion.

 

Water Injection - The process where water is injected back into the oil reservoir to maintain or increase pressure and stimulate production.

Wellhead: Permanent equipment used to secure and seal the casings and production tubing and to provide a mounting place for the Christmas trees.

 

Wireline: Equipment used to introduce tools into the well bore under pressure.

 

Workover: Re-entry into a completed well for modification or repair work.

 

Workover rig: Normally a smaller, portable version of the main drilling derrick which can be used to carry our work over operations on installations which do not have a permanent derrick.