Wells in which casings have been removed, and the well bore sealed with mechanical or cement plugs.
Producible lease
A lease where one well or several wells have discovered hydrocarbons in paying quantities, but for which there is no production during the reporting period.
Producible zone completion
The interval in a wellbore that has been mechanically pre- pared to produce oil, gas, or sulphur. There can be more than one zone completed for production in a wellbore.
Producing lease
A lease that is producing oil, gas, or sulphur in quantities sufficient to generate royalties.
Production
The phase of oil and gas operations involved with well fluids extraction, separation, treatment, measurement, etc.
Propane (C3H8)
Colourless, odourless gas of alkane series of hydrocarbons. It occurs in crude oil, in natural gas, and as a by-product of petroleum refining.
Proven reserves (Society of Petroleum Engineers)
Reserves that can be estimated with reasonable certainty to be recovered under current economic conditions. Current economic conditions include processing costs prevailing at the time of the estimate. Proved reserves must either have facilities that are operational at the time of the estimate to process and transport those reserves to market, or a commitment of reasonable expectation to install such facilities in the future. Proved reserves can be subdivided into undeveloped and developed.
Rent
Periodic payments made by the holder of a lease, during the primary lease term for the right to use the land or resources for purposes established in the lease.
Royalty
Payment, in value (money) or in kind, of a stated proportionate interest in production from mineral deposits by the lessees to the lessor. The royalty rate may be an established minimum, a sliding-scale, or a step-scale. A step-scale royalty rate increases by steps as the average production on the lease increases. A sliding-scale royalty rate is based on average production and applies to all production from the lease.
Sales value
The proceeds received for the sale of the mineral.
Service zone completion
The interval in a well bore that has been mechanically prepared for service use, usually water or gas injection to stimulate production from other wells or for water or other waste disposal.
Shut-in payments
Payments made for any producible well on the Federal OCS that is temporarily closed down.
Sour gas
Natural gas containing significant quantities of hydrogen sulphide.
Sulphur
A nonmetallic element that occurs in association with salt diapirs throughout much of the onshore and offshore Gulf of Mexico region. All offshore sulphur is mined by the Frasch process, which uses hot brine to melt sulphur out of the enclo- sing rock so the molten sulphur can be recovered.
Sulphur Dioxide (S02)
Acts as a precursor in formation of sulphate aerosols which, unlike greenhouse gases, have a net negative radioactive forcing effect and tend to cool Earth’s surface.
Suspended well
A well on which operations have been discontinued. The usual context is an uncompleted well in which operations ceased during drilling but which has not been plugged and abandoned permanently.
Synthetic Natural Gas (SNG)
Gases made from coals and other hydrocarbon-containing substances.
Well
A hole drilled or bored into the earth, usually cased with metal pipe, for the production of gas or oil. A hole for the injection under pressure of water or gas into a subsurface rock formation.
Workover
Operation on a shut-’in or producing well to restore or increase its production.
Wet Gas
Natural gas having significant amounts of heavier hydrocarbons in gasoline range.
Exploration
Aero-magnetic surveys
Magnetometers, towed by aircraft, help to detect magnetic anomalies or to distinguish geologic features that might appear similar from seismic data alone.
Air gun
Air gun array is most common technique used for seismic surveying offshore. Compressed air is released from a chamber to produce shock waves in earth.
Appraisal drilling
Drilling to determine physical extent, reserves and likely production rate of a reservoir, together with properties of oil or gas.
Appraisal well
A well drilled as part of an appraisal drilling programme.
Bottom-hole assembly
Components, together as a group, that make up lower end of drill-string (drill bit, drill collars, drill pipe and ancillary equipment).
Capping
Tightly closing a well so that hydrocarbons cannot escape.
Casing
Steel lining used to exclude unwanted fluids; control well pressures; support sides of well bore. Casing Seat - lowest point at which casing is set. Casing head - top of casing set in well; part of casing that protrudes above surface and to which control valves and flow pipes are attached.
Cement
Pumped into space between casing and well bore wall in order to hold casing in place.
Choke
Device to restrict rate of flow during testing of an exploratory discovery.
Circulation
Techniques for bringing cuttings from bottom of well bore to surface by continuously pumping drilling mud down through drill-string and up annulus during rotary drilling.
Coiled tubing
Used to carry production tubing to bottom of well.
Compensator
Keeps drill-sting stationary while semi-submersible and derrick move.
Conductor
Wide-diameter pipe from drilling platform to sea-bed to guide drilling and contain drilling fluid.
Deep-Water Discovery
An offshore discovery located in at least 200 metres of water.
Derrick
Elongated pyramid of latticed steel mounted over bore hole for suspending and rotating drill pipes.
Discovery well
An exploratory well that finds hydrocarbons.
Down hole
A term to describe tools, equipment and instruments used in well bore.
Drill bit
Located at end of drill-string cutting head is generally designed with three cone-shaped wheels tipped with hardened teeth. Drill bits used for extra-hard rock are studded with thousands of tiny industrial diamonds.
Drill collars
Heavy pipe-sections that put weight on drill bit.
Drill cuttings
Lifted continually to surface during drilling by a circulating-fluid system driven by a pump. To facilitate removal of cuttings, mud is constantly circulated down through drill pipe, out through nozzles in drill bit, and then up to surface through space between drill pipe and well bore through earth (diameter of bit is somewhat greater than that of pipe).
Drill-string
Series of connected 9 metre length drill pipes (joints).
Dry Hole
Unsuccessful well, drilled without finding commercial quantities of hydrocarbons.
Exploration
Search for hydrocarbons by Geological and Geophysical (G&G) surveys that may be followed by exploration drilling.
Exploration well
Drilling to determine whether hydrocarbons are present.
Farm-in
Transfer of part of an oil or gas interest in consideration for an agreement by transferee(s) to meet certain expenditure that would otherwise have to be undertaken by licensee(s).
Geophysics
Branch of science that applies physical principles to study of planet earth.
Gravity surveys
Measure density variations in local rock masses. Surveys are based on use of a gravimeter down bore holes.
Horizontal Drilling
Technique for cutting a bore hole in geological strata in a horizontal, rather than normal vertical, direction.
Kick
Back pressure in well from invading oil/gas/water.
Killing a well
Filling bore with drilling mud of suitable density to stop flow of oil / gas.
Liner
Small diameter casing extending into producing layer from just inside bottom of final string of casing cemented in a well.
Modular formation dynamics tester
Measures fluid pressures and collects small samples in a well.
Plugging
Process whereby a well that is no longer needed is filled with concrete and abandoned.
Rotary Drilling
Being coupled to rotating table on derrick floor rotates drill-string.
Rotary Table/Drilling Table
Turning device on derrick floor in which drill-string is held and rotated.
Round trip
Complete process of pulling out and running in drill-string.
Seismic surveys
Measurements of seismic-wave travel. Seismic exploration is divided into refraction and reflection surveys, depending on whether the predominant portion of the seismic waves’ travel is horizontal or vertical. Refraction seismic surveys are used in exploration. Seismic reflection surveys detect boundaries between different kinds of rocks; this detection assists in mapping of geologic structures.
Shale shaker
Drilling mud passed over to sieve out cuttings.
Sidetrack Drilling
A remedial operation that results in creation of a new section of well bore for purpose of detouring around «junk», redrilling a lost hole or straightening crooked holes.
Spud
Commencement of drilling operations.
Suspended discovery
An oil or gas field identified by a discovery well but not being produced or developed.
Three-dimensional Seismic/3-D Seismic Three-dimensional images created by bouncing sound waves off underground rock formations; used to determine best places to drill for hydrocarbons.
Top drive
Powerful electric motor that rotates whole drill-string from top down.
Well Nomenclature (E&A)
Appraisal (APP)
Deviated (DEVW)
Discovery (DISC)
Exploration (EXP)
Junked & Abandoned (JA)
Plugged & Abandoned (PA)
Re-entry (RE)
Suspended (SP)
Testing (TE)
Tight Hole (TIGHT)
Wildcat
Exploration well drilled in an unproven area. (Term wild- catter comes from West Texas, where in early 1920s drilling crews encountered many wildcats as they cleared locations for exploratory wells. Shot wildcats were hung on oil derricks, and wells became known as wildcat wells.)
Production
Abandonment/Decommissioning
Process of dismantling wellhead, production and trans- portation facilities and restoration of depleted producing areas in accordance with licence requirements and/or legislation.
Acid stimulation
Form of hydrochloric acid is pumped down well hole to en- large pore space in oil bearing rocks to increase flow and reco- very.
Acoustic log
Record of time taken by a sound wave to travel over a certain distance through geological formations.
Air injection
An enhanced recovery technique in which air is injected into hydrocarbon formation to increase reservoir pressure.
Artificial lift
Any techniques, other than natural drives, for bringing oil to surface.
Blow-down
Condensate and gas produced simultaneously from outset of production.
Casing perforation
Holes made in liner of a finished well to allow hydrocarbons to flow into production tube.
Cathodic protection
Method used to minimise rate of electrochemical corrosion of structures, for example, installations offshore, pipelines and storage tanks.
Christmas tree
Branching series of pipes, gauges and valves on top end of each production well to control flow of oil or gas.
Closed-in
Descriptive of a well that is capable of producing, but is not currently producing.
Coiled tubing
Used to carry production equipment to bottom of well.
Commingling
Producing oil and gas from two or more reservoirs at different depths, or where product of two or more fields is transported via a common pipeline.
Delineation well
Drilled at a distance from a discovery well to determine physical extent, reserves and likely production rate of a new oil or gas field.
Deviated well
Horizontal well drilled at an angle (over 80 degrees) to vertical.
Development
Phase on which a proven oil or gas field is brought into production by drilling production (development) wells.
Development well
A production well drilled with intent of producing oil or gas from a proven field.
Dual Completion
A well completed to produce from two separate reservoirs.
Enhanced reach
Deviated wells (over 65 degrees) from vertical and reach out horizontally more than twice vertical depth.
Field
Geographical area under which an oil or gas reservoir lies.
Field Nomenclature
Field ceased production (FCP)
Field under development (FUD)
Field in production (FIP)
Flaring and venting
Flaring is burning of hydrocarbon gases for commercial or technical reasons. Venting is release of gases to atmosphere.
Flare Stack
Steel structure on an offshore installation or at a proces- sing facility from which gas is flared.
Gas Cap
In field containing both gas and oil, some gas will often collect at top of reservoir in a single deposit.
Gas/Condensate field
Reservoir containing both natural gas and oil, with greater proportion of gas. Condensate appears when gas is drawn from well, and its temperature and pressure change sufficiently for some of it to became liquid petroleum.
Gas field
Field containing natural gas, but no oil.
Gas gathering system
Central collection point for offshore gas fields. Production is then piped to central processing system onshore.
Gas Injection (GI)
Associated gas is pumped back into a reservoir to maintain reservoir pressure. In this way rate of production of crude oil also can be increased.
Gas lift
Gas from same or nearby field is mixed with oil in tubing to lessen weight of liquid column.
Gas Processing
Separation of oil and gas, and removal of impurities and NGLs from natural gas.
Gas Treatment
Removal of impurities, condensate, hydrogen sulphide and NGLS from natural gas.
Gravity Structures
Either concrete or hybrid (concrete base and steel legs and superstructure) structures that due to weight rest on seabed or piled into it.
Horizontal well
Used when reservoir permeability is low or hydrocarbons are being produced from vertical fractures in rock.
Jacket
Supporting (concrete base or steel legs) structure for an offshore installation.
Marine Riser
Pipe connecting offshore installation to a subsea wellhead or pipeline for drilling or production purposes.
Module
Self-contained box or package built with a specific purpose (for example, well head, oil and gas separation, gas compression, platform power generation, mud, storage, diesel, filter and exhaust) located on production installations.
Multilateral well
More than one horizontal section drilled in one well. Used to maximise number of wells that can be drilled from small installations.
Odorant
Substance (for example mercaptan) added to odourless natural gas or NGLs to enable detection.
Offshore Oil Loading Nomenclature Single buoy mooring (SBM)
Single point mooring (SPM)
Exposed location single buoy mooring (ELSBM)
Spar
Enables offshore loading with vessel swinging to present least resistance to prevailing wind or current conditions.
Oil in Place (OIP)
Estimation of real amount of oil in a reservoir. Higher value than recoverable reserves of reservoir.
Pig
Device for cleaning a pipeline or separating two liquids being moved down pipeline. (Intelligent pig - fitted with sensors to check for corrosion or defects in pipelines.)
Piling
Long steel piles driven into the seabed to anchor fixed offshore structures solidly in place.
Pipeline
A pipe through which natural gas, crude oil or petroleum products are pumped between two points, either onshore or offshore.
Plateau
Level of peak oil or gas field production; it is always followed by declining level of production.
Platform
Fixed structure resting on seabed or piled into it. Platform Nomenclature
Tension Leg Platform (TLP)
Minimum Facility Platform (MINF)
Not Normally Attended Installation (NNAI)
Gravity based structures (GBS)
Accommodation (ACCOM)
Compression (COMP)
Drilling (DRIL)
Riser (RISE)
Preventative maintenance
Maintenance carried out prior to unit or system failure.
Primary Recovery
Recovery of hydrocarbons from a reservoir using only na- tural reservoir pressure.
Produced Water
Brines naturally present or injected into reservoir to enhance production. Produced along side oil production.
Production Drilling
Drilling of wells in order to bring a field into production.
Production Installation
An installation from which development wells are drilled and that carries all associated processing plants and other equipment needed to maintain a field in production.
Production String
Tubing or piping in a production well through which oil or gas flows from reservoir to wellhead.
Recovery Factor
Ratio of recoverable oil and / or gas to estimated oil and / or gas in place in reservoir. Determined by a various factors such as reservoir dimensions, pressure, nature of hydrocarbons, and development plan, (see also Primary, Secondary and Tertiary Recovery.)
Redetermination
Retroactive adjustment to relative percentage interests of joint venturers in a field.
Reserves: Possible
Reserves at present cannot be regarded as “probable”.
Reserves: Probable
Reserves not yet “proven”, but are estimated to have a better than 50% chance of being technically and economically producible.
Reserves: Proven
Reserves which on available evidence are virtually certain to be technically and economically producible.
Reservoir
Subsurface, porous, permeable rock formation in which hydrocarbons are present.
Reservoir drive
Powered by difference in pressures within reservoir and well.
Reservoir engineering model
Used to predict reservoir behaviour during production to enable selection of most efficient method of recovery.
Satellite Installation
An offshore structure that depends on another installation for materials or services.
Secondary Recovery
Recovery of hydrocarbons from a reservoir by increasing reservoir pressure by injecting gas or water into reservoir rock, (see also Primary and Tertiary Recovery.)
Slug catcher
Plant installed in a gas pipeline system to catch unwanted “slugs” of liquid.
Subsea manifolds
Allows wells to be put on production without need to build a platform to operate and maintain wells.
Sub-sea wellhead
A wellhead installed on the sea floor and controlled remotely from a platform, a floating production facility or land.
Substructure
Support form of an offshore installation on which derrick, engines, helicopter pad, cranes, etc. are installed.
Tension Leg Platform .
A floating offshore structure held in position by a number of tension-maintaining cables anchored to seabed. Cables dampen wave action to keep platform stationary.
Terminal
Onshore transit installation that receives oil or gas from offshore production facilities via pipeline and/or tankers. Plant and equipment designed to receive and process crude oil or gas to remove water and impurities.
Tertiary Recovery
Recovery of hydrocarbons from a reservoir by sophisticated methods, for example, heating reservoir or enlarging pore spaces using chemicals, (see also Primary and Secondary Recovery)
Tubing
Piping installed in wells for production of oil and gas.
Topsides
Top of an installation positioned on jacket.
Water Injection (WI)
Water is pumped into alternate wells in a field. Pressure in reservoir as à whole can be maintained or increased and production can be maintained or increased.
Well Nomenclature (Field)
Development (DEV)
Deviated (DEVW)
Gas Injection (GI)
Water Injection (WI).
Workover
Re-entry into a completed field well for modification or repair. Restoring well productivity by cleaning out accumulations of sand, silt or other substances that clog production tubing.
Measures
API gravity
Scale used to express specific gravity of oils. Higher API gravity, lighter oil.
Atmospheric pressure
Weight of atmosphere on surface of Earth. At sea level ap- prox. 1.013 bars.
Bar
One bar = 100 kPa Barrel (bbl)
7.3 bbls = One tonne: 6.29 bbls = One cubic metre: One bbl = 159 litres approx. bcf
Billion Cubic Feet (One bcf = 0.176 Mboe) bcm
Billion Cubic Metres (One bcm = 0.83 MToe)
Billion
One thousand million (109)
Block
UKCS acreage one thirtieth of a quadrant (approx. 200 - 250 sq. kms). Generally defined in terms of latitude and longitude, at one-degree intervals, bopd / boe
bbls of oil per day / bbls of oil equivalent.
Brent blend
International marker for crude oil pricing based on a blend of North Sea crudes.
British Thermal Unit (BTU)
One BTU or Btu = 1.05506 kJ = 0.293 watt-hour
Calorific equivalents
One cubic foot of gas = 1000 BTUs = 1055.06 kJ Approx. one million tonnes of oil = 40 x 1012 BTUs = 40,400 MJ
Candela
SI unit of light intensity defined as 1/60 of the light radia- ted from a sq. cm of a blackbody, a perfect radiator that ab- sorbs no light, held at the temperature of freezing platinum.
Cubic foot
Standard unit used to measure quantity of gas at atmospheric pressure (One cubic foot = 0.0283 cubic metres).
Cubic metre
Si unit used to measure quantity of gas at atmospheric pressure (One cubic metre = 35.31 cubic feet).
Dead Weight (dwt)
Difference between loaded and unloaded weights of a ship. Exposure
Measurement of time during which subject is at risk from , a hazard.
Gas Oil Ratio (GOR)
Volume of gas at atmospheric pressure produced per unit of oil produced.
Joule (j)
Derived SI unit of work or energy.
Gigajoule = One million joules I* 278 kWh.
Kilocalorie (kcal)
One thousand calories.
Kilogram (kg)
SI unit of mass. One thousand grams.
Kilopascal (kPa)
Defined as pressure of 0.0102 kg / sq. cm
Kilowatt-hour (kWh)
One kWh = 3.6 MJ« 3,412 BTU = 860 kcal P 0.0949 cubic metres of gas) m / mcf
Thousands / Thousands of Cubic Feet (of Gas)
mm / M
Millions
mmbbls / mmboe
Million bbls / Million bbls of oil equivalent
nunscf / mmscfd
Millions of Standard Cubic Feet (of Gas) /
Millions of Standard Cubic Feet per Day (of Gas)
Mtc
Million tonnes of carbon
MtCH4
Million tonnes of methane
MtC02
Million tonnes of carbon dioxide
Mboe / MToe
Million bbls of oil equivalent /
Million tonnes of oil equivalent
Oil Equivalent
Method of assessing work of calorific value of different sources of energy in terms of one tonne of oil.
ppb / ppm
parts per billion / parts per million
psi
Pounds per square inch One psi = 6.89 kPa
Quadrant
UKCS acreage one degree by one degree. 30 Blocks to Quadrant.
Specific Gravity
Ratio of density of a substance at a particular temperature to density of water.
SI unit
Self-consistent system of measurement units based on the MKS (metre-kilogram-second) system. Adopted for interna- tional use under Le Systume International d’Unitôs, now employed for all scientific and most technical purposes.
Square kilometres (Sq. kms / Km2)
1000res x 1000 metres, One Km2 (100 hectares) =
0.3861 sq. miles Square Miles
One Sq Mile (640 acres) = 2.590 Km2
tcf
Trillion (a million million) Cubic Feet (of Gas)
Tonne (t)
Metric tonne = 1000 kilograms
Watt (W)
Power which in one second gives rise to energy of one joule (j). Kilowatt (kW) = One kW = 1000 watts.
Megawatt (MW) = One million watts.
Gigawatt (GW) = Thousand megawatts.
Environment
Air Emissions
Waste gases, vapours and small particles released into air.
Environment
External surroundings and conditions in which a company or an individual operates or which may effect, including living systems therein.
Environmental controls
Put in place to meet or exceed legal requirements and to minimise impact on environment.
Environmental Impact Assessment (EIA)
Part of project management concerned with identifying through a formal written technical evaluation likely impact (positive and negative) of a proposed development or activity on natural and man-made environment.
Environmental Management Systems (EMS)
A process that examines environmental factors and activities or processes that industry uses.
Generic Hazard
Hazard which may be generally present throughout an operation or industry, but which may have widely different levels of risk, depending on specific site characteristics.
Hazard
Object, physical effect, or a condition with potential to harm persons, property or environment.
Reasonably Practicable
Risk reduced to levels such that further risk reduction measures would be so disproportionate to probability and consequence that it
would be objectively unreasonable to implement them.
Risk
Measure of likelihood of occurrence of an undesirable event and of potentially adverse consequences.
Risk Assessment
Careful consideration by competent persons of hazards associated with a task. Potential effect of each hazard, how serve it might be and likelihood of it occurring, should be considered to determine effort required to make site as safe as reasonably practicable.
Risk Management
System that eliminates or mitigates threat from hazards.
Pipelines
Battery
Small field plants which remove natural gas, NGLs, water and sand from crude oil delivered by gathering systems from individual wells.
Bitumen
Petroleum that exists in the semi-solid or solid phase in natural deposits; a thick, sticky form of crude that must be heated or diluted before it will flow into a well or through a pipeline. Bitumen generally has an API gravity of less than ÍÃ.
Burst strength
Hydraulic pressure required to burst a pipe or vessel of given thickness. Generally 2.5 to 4.0 times working pressure.
Compressor
A machine used to boost natural gas pressure to move it through pipelines or other facilities. A compressor station is a permanent facility housing one or more compressors.
Crude oil
A naturally occurring liquid mixture of hydrocarbons; liquid petroleum. The liquid hydrocarbons may be mixed with
natural gas, carbon dioxide, saltwater, sulphur compounds and sand. Most of these substances are separated from the liquid hydrocarbons at processing facilities near the producing field.
Delivery stations
Facilities where natural gas or crude oil are transferred from one party to another.
Diesel or diesel fuel is a specific fractional distillate of petroleum fuel oil that is used as fuel in a diesel engine.The term typically refers to fuel that has been processed from petroleum, but increasingly, alternatives such as biodiesel or biomass to liquid (BTL) or gas to liquid (GTL) diesel that are not derived from petroleum are being developed and adopted. For clarity, petroleumderived diesel is increasingly called petrodiesel.
Fabricated assemblies
Pipeline components such as valves, pumps and pipe fittings.
Heavy oil
Oil having an API gravity less than 22.3e. Includes some oil that will flow, however slowly, but most heavy oil requires heat or dilution to flow to a well or through a pipeline.
Hydrocarbons
A large class of liquid, solid or gaseous organic compo- unds, consisting of only carbon and hydrogen, which are the basis of almost all petroleum products.