Glossary
Abandonment
(wells) Actions taken to ensure permanent isolation of the fluids and pressures of exposed permeable zones within a well from the surface and from lower pressured zones
Abatement
Reduction in the degree or intensity of emissions or other pollutants
Absorption
Chemical or physical take-up of molecules, atoms or ions into the bulk of a solid or liquid, forming either a solution or compound
Accounting
Activities aiming to document and report avoided CO2 emissions for a project
Acid gas
Any gas mixture that turns to an acid when dissolved in water (normally refers to H2S + CO2 from sour gas)
Adiabatic
A process in which no heat is gained or lost
Adsorption
The adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface
Aluminosilicate mineral
Natural mineral – such as feldspar, clays, micas, amphiboles – composed of Al2O3 and SiO2 plus other cations
Amine
Organic chemical compound containing one or more nitrogens in -NH2, -NH or -N groups
Anhydrite
Anhydrous calcium sulphate, its common hydrous form is called gypsum
Anthracite
Hard, compact variety of coal that has a high luster; it has the highest carbon content, the fewest impurities, and the highest calorific content of all types of coal
Anthropogenic source
Source which is man-made as opposed to natural
Anticline
Folded geological strata that is convex upwards
API
American Petroleum Institute; degree API is a measure of oil density
Aquifer
An underground layer of fluid-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) with significant permeability to allow flow
Assessment unit
(petroleum) A volume of rock within the total petroleum system that contains fields (discovered and undiscovered) which share similar geological traits and socioeconomic factors
Atmosphere
The layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%)
Bamako Convention 1991
Bamako Convention on the Ban on the Import into Africa and the Control of Transboundary Movement and Management of Hazardous Wastes within Africa
Barrier formations
(in CO2 storage) Underground geological layers that hinder the vertical movement of the CO2 plume.
Basalt
A type of basic igneous rock which contains less than 20% quartz and less than 10% feldspar, where at least 65% of the feldspar is in the form of plagioclase
Basalt formations
Basaltic rocks such as lava flows that may have porosity and permeability in the fractures or cavities between blocks of solid rock
Basel Convention
UN Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal, which was adopted at Basel on 22 March 1989
Basin
A geological region with sedimentary strata dipping towards a common axis or centre
Bathymetric
Pertaining to the depth of water
Benthic
Relating to the bottom of a sea or lake or to the organisms that live there
Bicarbonate ion
The anion formed by dissolving carbon dioxide in water, HCO3-
Biomass
Biological material derived from living or recently living organisms, usally referring to plants
Biomass-based CCS
Carbon capture and storage in which the feedstock is biomass
Bituminous coal
An intermediate rank of coal falling between the extremes of peat and anthracite, and closer to anthracite
Blow-out
(well) Refers to catastrophic failure of a well when the petroleum fluids or water flow unrestricted to the surface
Bulk CO2
Unprocessed gaseous CO2, with a CO2 content typically in excess of 95%
Buoyancy
Tendency of a fluid or solid to rise through a fluid of higher density
Capillary entry pressure
Additional pressure needed for a liquid or gas to enter a pore and overcome surface tension
Capillary trapping
Immobilisation of a fraction of in-situ fluids by capillary forces
Caprock
Rock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir
Capture
The separation of carbon dioxide from other gases before it is emitted to the atmosphere
Capture efficiency
The fraction of CO2 separated from the gas stream of a source
Carbon credit
A convertible and transferable instrument that allows an organisation to benefit financially from an emission reduction
Carbon trading
A market-based approach that allows those with excess emissions to trade that excess for reduced emissions elsewhere
Carbonate
Natural minerals (e.g. calcite, dolomite, siderite, limestone) composed of various anions bonded to a CO32- cation
Carbonate neutralization
A method for storing carbon in the ocean based upon the reaction of CO2 with a mineral carbonate such as limestone to produce bicarbonate anions and soluble cations
Casing
A pipe which is inserted to stabilise the borehole of a well after it is drilled
CCGT
Combined Cycle Gas Turbine
CCS
Carbon dioxide Capture and Storage
CDM
Kyoto Protocol’s Clean Development Mechanism
Certification
In the context of carbon trading, certifying that a project achieves a quantified reduction in emissions over a given period
CGS
CO2 Geological Storage; Injection accompanied by storage of CO2 streams in underground geological formations.
Chlorite
A magnesium-iron aluminosilicate sheet silicate clay mineral
Class “x” well
A regulatory classification for wells used for the injection of fluids into the ground
Cleat
The system of joints, cleavage planes, or planes of weakness found in coal seams along which the coal fractures
Closing contour
The lowest structural contour that contains the structure; measurements of both the areal closure and the distance from the apex to the lowest closing contour are typically incorporated in calculations of the estimated hydrocarbon content of a trap
CO2 avoided
The difference between CO2 captured, transmitted and/or stored, and the amount of CO2 generated by a system without capture, net of the emissions not captured by a system with CO2 capture
CO2 equivalent
A measure used to combine emissions of different greenhouse gases based on their global warming potential
CO2 plume
Dispersing volume of CO2-rich phase contained in target formation
CO2 stream
A flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage
Completion
(well) Refers to the cementing and perforating of casing and stimulation to connect a well bore to reservoir
Containment
Restriction of the movement of a fluid to a designated volume (e.g. reservoir)
Continental shelf
The extended perimeter of each continent and associated coastal plain submerged under relatively shallow seas
Contingency plan
Plan to implement corrective measures if a significant irregularity occurs
Corrective measure
Measure taken to correct (remediate) significant irregularities or to prevent or stop leakages of CO2 from the storage volume
Critical point
The highest temperature and pressure at which a substance can exist as a vapour and liquid phase in equilibrium
Dawsonite
A mineral: dihydroxide sodium aluminium carbonate
Deep saline aquifer
A deep underground rock formation composed of permeable materials and containing highly saline fluids
Deep sea
The sea below 1000m depth
Demonstration phase
Demonstration phase means that the technology is implemented in a pilot project or on a small scale, but is not yet economically feasible at full scale
Dense fluid
A gas compressed to a density approaching that of the liquid
Depleted
(hydrocarbon reservoir) one where production is significantly reduced
Depleted gas field
Reservoir rock where most of the gas has been extracted from between the grains of rock
Depleted oil field
Reservoir rock where most of the oil has been extracted from between the grains of rock
Diagenesis
Processes that cause changes in sediment after it has been deposited and buried under another layer
DIC
Dissolved Inorganic Carbon
Dip
(geology) The steepest angle of descent of a tilted rock strata or feature relative to a horizontal plane
Discharge
The amount of water issuing from a spring or in a stream that passes a specific point in a given period of time
Discordant sequence
(geology) sequence of rock strata that is markedly different from strata above or below
Dolomite
A magnesium-rich carbonate mineral (CaMgCO3), also the corresponding sedimentary rock
Down-hole log
Record of conditions in a borehole
Drill cuttings
The solid particles recovered during the drilling of a well
Drill string
The assembly of drilling rods that leads from the surface to the drilling tool
Drive
Fluid flow created in formations by pressure differences arising from borehole operations
Dry ice
Solid carbon dioxide
ECBM
Enhanced coalbed methane recovery: the use of CO2 to enhance the recovery of the methane present in unminable coal beds through the preferential adsorption of CO2 on coal
ECBMP
Enhanced coalbed methane production
EGR
Enhanced Gas Recovery: the recovery of gas additional to that produced naturally by fluid injection or other means
EGS
Enhanced Geothermal Systems
EIA
Environmental Impact Assessment
Emission factor
A normalised measure of GHG emissions in terms of activity, e.g. tonnes of GHG emitted per tonne of fuel consumed
Emissions credit
A commodity giving its holder the right to emit a certain quantity of GHGs
Emissions trading
A trading scheme that allows permits for the release of a specified number of tonnes of a pollutant to be sold and bought
Endothermic
Concerning a chemical reaction that absorbs heat, or requires heat to drive it
Enhanced gas recovery
The recovery of gas additional to that produced naturally, achieved by fluid injection or other means
Enhanced oil recovery
The recovery of oil additional to that produced naturally, achieved by fluid injection or other means
EOR
Enhanced Oil Recovery: the recovery of oil additional to that produced naturally, achieved by fluid injection or other means
EOS
Equation of State: a thermodynamic equation which describes the state of matter under a given set of physical conditions
ETS
Emissions Trading System, defined in the EU ETS Directive 2003/87/EC amended by Directive 2009/29/EC
EU CCS Directive
Directive 2009/31/EC of the European Parliament and of the Council of 23 April 2009 on the geological storage of carbon dioxide
Evaporite
A water soluble rock formed by evaporation from an aqueous solution
Exothermic
Concerning a chemical reaction that releases heat, such as combustion
Extended reach well
Borehole that is diverted into a more horizontal direction to extend its reach
Far field
A region located far from a signal source
Fault
(geology) A surface at which strata are no longer continuous, but are found displaced
Fault reactivation
The tendency for a fault to become active, i.e. for movement to occur
Fault slip
The extent to which a fault has slipped in past times
Feldspar
A group of alumino-silicate minerals (K, Na)AlSi3O8 - CaAl2Si2O8 that makes up much of the Earth’s crust
Flood
(reservoir) The injection of a fluid into an underground reservoir
Folding
(geology) The bending of sedimentary rock strata from the plane in which they were formed
Formation
A body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it
Formation water
Water that occurs naturally within the pores of rock formations
Fossil fuel
Oil, gas and coal are fossil fuels, formed over millions of years from the remains of plants and animals (fossils); they are hydrocarbons
Fracture
Any break in rock along which no significant movement has occurred
Fugitive emission
Any releases of gases or vapours from anthropogenic activities such as the processing or transportation of gas or petroleum
G8
The Group of Eight (forum of senior offical representatives from France, Germany, Italy, Japan, United Kingdom, United States of America, Canada, Russia)
Gasification
Process by which a carbon-containing solid fuel is transformed into a carbon- and hydrogen-containing gaseous fuel by reaction with air or oxygen and steam
GCCSI
Global Carbon Capture and Storage Institute
Geochemical trapping
The retention of injected CO2 by geochemical reactions
Geological formation
A lithostratigraphic subdivision within a sedimentary succession within which distinct rock layers can be found and mapped
Geological setting
The geological environment
Geological time
The time over which geological processes have taken place
Geomechanics
The science of the movement of the Earth’s crust an rocks
Geosphere
The earth, its rocks and minerals, and its waters
Geothermal
Concerning heat flowing from deep in the earth
GHG
Greenhouse gases: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydroflurocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6)
GHG IA
Implementing Agreement for a Co-operative Programme on Technologies Relating to Greenhouse Gases Derived from Fossil Fuel Use (IEA Greenhouse Gas R&D Programme)
Greenfields
(in CO2 storage) Geological formations where no hydrocarbon production has occured within the potential storage area; (in CO2 capture) New facilities where no previously exists
Greenhouse gas
Gas in the atmosphere that absorbs and emits infrared radiation emitted by the Earth’s surface, the atmosphere, and clouds; thus, trapping heat within the surface-troposphere system. e.g. water vapour (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), ozone (O3), sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs)
Henry’s Law
States that the solubility of a gas in a liquid is proportional to the partial pressure of the gas in contact with the liquid
HHV
Higher heating value: the energy released from the combustion of a fuel that includes the latent heat of water
Host rock
(geology) The rock formation that contains a foreign material
HSE
Health, safety and environment
Hydrate
A solid compound containing water molecules combined in a definite ratio together with CO2, CH4 or similar gases as an integral part of the crystal
Hydraulic unit
Hydraulically connected pore space where pressure communication can be measured by technical means and which is bordered by flow barriers, such as faults, salt domes, lithological boundaries, or by the wedging out or outcropping of the formation.
Hydrodynamic trap
A geological structure in which fluids are retained by low levels of porosity in the surrounding rocks
Hydrogeological
Concerning water in the geological environment
Hydrostatic
Pertaining to the properties of a stationary body of water
Hysteresis
The phenomenon of a lagging recovery from deformation or other disturbance
IEA
International Energy Agency
IEA GHG
International Energy Agency – Greenhouse Gas R&D Programme
IGCC
Integrated Gasification Combined Cycle: power generation in which hydrocarbons or coal are gasified and the gas is used as a fuel to drive both a gas and a steam turbine
Igneous
Rock formed when molten rock (magma) has cooled and solidified (crystallised)
Immature basin
A basin in which the processes leading to oil or gas formation have started but are incomplete
Injection
The process of using pressure to force fluids down wells
Injection well
A well in which fluids are injected rather than produced
Injectivity
A measure of the rate at which a quantity of fluid can be injected into a well
In-situ mineralisation
A process where minerals are not mined: carbon dioxide is injected in the silicate formation where it reacts with the minerals, forming carbonates and silica
IPCC
Intergovernmental Panel on Climate Change
IPCC 2005
IPCC 2005 Special Report on Carbon Dioxide Capture and Storage
Kyoto Protocol
Protocol to the United Nations Framework Convention on Climate Change, which was adopted at Kyoto on 11 December 1997
Lateral seal
Geological structure that impedes the movement of fluids horizontally
LCA
Life Cycle Assessment
Leach
To desolve a substance from a solid
Leakage
(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column
LHV
Lower heating value: energy released from the combustion of a fuel that excludes the latent heat of water
Lignite/sub-bituminous coal
Relatively young coal of low rank with a relatively high hydrogen and oxygen content
Limestone
A sedimentary rock made mostly of the mineral calcite (calcium carbonate), usually formed from shells of dead organisms
Lithology
The nature and composition of rocks
Lithosphere
The outer layer of the Earth, made of solid rock, which includes the crust and uppermost mantle up to 100 km thick
LNG
Liquified Natural Gas
Log
(well) Records taken during or after the drilling of a well
London Convention
International convention on the prevention of marine pollution by dumping of wastes and other matter, which was adopted at London, Mexico City, Moscow and Washington on 29 December 1972
London Protocol
Protocol to the London Convention, adopted in London on 2 November 1996 but which had not entered into force at the time of writing
LPG
Liquified Petroleum Gas
Mafic
Term used for silicate minerals, magmas, and rocks, which arerelatively high in the heavier elements
Magmatic activity
The flow of magma (lava)
Maturation
(geology) The process of changing with time; e.g. the alteration of peat into lignite, then into sub-bituminous and bituminous coal, and then into anthracite
Mature sedimentary basins
Geological provinces formed by the deposition of particulate matter under water when the deposits have matured into hydrocarbon reserves
mD
A non-SI unit of permeability, milli Darcy, and approximately equal to 1μm2
Medium-gravity oil
Oil with a density of between about 850 and 925kg/m3 (between 20 and 30 API)
Metamorphic
Rocks that have been altered by heat and/or pressure
Mica
Class of silicate minerals with internal sheet like structure
Microseismicity
Small-scale seismic tremors
Migration
The movement of fluids in reservoir rocks
Mineral trap
A geological structure in which fluids are retained by the reaction of the fluid to form a stable mineral
Mineralisation
Is a natural form of geologically storing CO2 by the very slow reaction between CO2 and naturally occurring minerals, such as magnesium silicate, to form the corresponding mineral carbonate
Miscible displacement
Injection process that introduces miscible gases into the reservoir, thereby maintaining reservoir pressure and improving oil displacement
Mitigation
The process of reducing the impact of any failure
Monitoring
Measurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions
Monte Carlo
A modelling technique in which the statistical properties of outcomes are tested by random inputs
MRG
In line with the EU ETS Directive, the Commission has adopted guidelines for the monitoring and reporting of greenhouse gas emissions, known as the "MRG"
Mudstone
A very fine-grained sedimentary rock formed from mud
Natural analogue
A natural occurrence that mirrors in most essential elements an intended or actual human activity
Natural gas
Gas stored underground; It consists largely of methane, but can also contain other hydrocarbons, water, hydrogen sulphide and carbon dioxide, these other substances are separated before the methane is put into a pipeline or tanker
Natural underground trap
A geological structure in which fluids are retained by natural processes
Navier-Stokes equations
The general equations describing the flow of fluids
Near-field
The region located close to a signal source
NGCC
Natural Gas Combined Cycle: natural-gas-fired power plant with gas and steam turbines
Observation well
A well installed to permit the observation of subsurface conditions
OSPAR
Convention for the Protection of the Marine Environment of the North-East Atlantic, which was adopted at Paris on 22 September 1992
Outcrop
The point at which a particular rock formation reaches the earth’s surface
Overburden
Rocks and sediments above any particular stratum
Overpressure
Pressure created in a reservoir that exceeds the pressure inherent at the reservoir depth
Oxidation
The loss of one or more electrons by an atom, molecule, or ion
Partial pressure
The pressure that would be exerted by a particular gas in a mixture of gases if the other gases were not present, e.g. pCO2 ishe partial pressure of CO2
PC
Pulverized coal: usually used in connection with boilers fed with finely ground coal
Permeability
Ability to flow or transmit fluids through a porous solid such as rock
Permian
A geological age between 290 and 248 million years ago
PFC
Perfluorated hydrocarbons
Point source
An emission source that is confined to an identifiable location/region
Pore space
Space between rock or sediment grains that can contain fluids
Poroelastic
Elastic behaviour of porous media
Porosity
Measure for the amount of pore space in a rock
Post-closure
Period after transfer of responsibility to the competent authority
Post-combustion capture
The capture of carbon dioxide after combustion
Pre-combustion capture
The capture of carbon dioxide following the processing of the fuel before combustion
Preventive measure
Measure taken to prevent hazards from occurring; either by reducing the probability that it occurs or by minimising potential damages or negative consequences
Rank
(coal) Quality criterion for coal
Redox
Reduction-oxidisation reaction
Reduction
The gain of one or more electrons by an atom, molecule, or ion
Reservoir
A subsurface body of rock with sufficient porosity and permeability to store and transmit fluids
Residual saturation
The fraction of the injected CO2 that is trapped in pores by capillary forces
Risk
Concept that denotes the product of the probability of a hazard and the subsequent consequence of the associated event
Risk assessment
A process intended to calculate or estimate the risk to a given target, part of a risk management system
Saline formation
Underground rock where saline water occupies the tiny spaces between the grains of rock
Saline groundwater
Groundwater in which salts are dissolved
Sandstone
Sand that has turned into a rock due to geological processes
Saturated zone
Part of the subsurface that is totally saturated with groundwater
Scenario
A plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts
Seabed
Boundary between the free water and the top of the seabottom sediment
Seal
An impermeable rock that forms a barrier above and around a reservoir such that fluids are held in the reservoir
Secondary recovery
(oil) Recovery of oil by artificial means, after the natural production mechanisms like overpressure have ceased
Sedimentary basin
Natural large-scale depression in the earth’s surface that is filled with sediments
Seismic profile
A two-dimensional seismic image of the subsurface
Seismic technique
Measurement of the properties of rocks by the speed of sound waves generated artificially or naturally
Seismicity
The episodic occurrence of natural or man-induced earthquakes
Shale
Clay that has changed into a rock due to geological processes
Shale formation
Is characterised by thin horizontal layers of rock with very low permeability, especially in the vertical direction; it is the most common sedimentary rock
Significant irregularity
Any irregularity in the injection or storage operation or in the condition of the storage volume itself, which implies the risk of a leakage or risk to the environment or human health
Sink
(CO2) The natural uptake of CO2 from the atmosphere, typically in soils, forests or the oceans
Solid hydrate
When an excess of CO2 is present in relatively cold ocean water (below 8°C) a solid hydrate can form consisting of six water molecules that make a cage around one CO2 molecule
Solubility trapping
A process in which fluids are retained by dissolution in liquids naturally present
Sour gas
Natural gas containing significant quantities of acid gases like H2S and CO2
Source
Any process, activity or mechanism that releases a greenhouse gas, an aerosol, or a precursor thereof into the atmosphere
Speciation
The determination of the number of species into which a single species may evolve over time
Spill point
The structurally lowest point in a structural trap that can retain fluids lighter than background fluids
Stimulation
(well) The enhancement of the ability to inject fluids into, or recover fluids from, a well
Storage
(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere
Storage capacity
The accumulated mass of CO2 that can be stored environmentally safely, i.e., without causing leakage of CO2 or native reservoir fluids or triggering geologic activity that has a negative impact on human health or the environment
Storage complex
The storage site and surrounding geological domain which can have an effect on overall storage integrity and security; that is, a primary containment system and any secondary containment system.
Storage site
Defined volume used for CO2 geological storage including the storage complex, overburden and the associated storage and injection facilities
Stratigraphic
The order and relative position of geological strata
Stratigraphic column
A column showing the sequence of different geological strata
Stratigraphic trap
A sealed geological formation capable of retaining fluids, formed by changes in rock type or facies
Structural trap
Geological structure capable of retaining hydrocarbons, sealed structurally by a fault or fold
Structure
(geology) Geological feature produced by the deformation of the Earth’s crust, such as a fold or a fault; a feature within a rock such as a fracture; or, more generally, the spatial arrangement of rocks
Structure contour map
Map showing the contours of geological structures
Sub-bituminous coal
Coal of a rank between lignite and bituminous coal
Supercritical
(CO2) Conditions where carbon dioxide has some characteristics of a gas and some of a liquid
Syngas
Synthesis gas: gas mixture that contains varying amounts of carbon monoxide and hydrogen
Tectonically active area
Area of the Earth where deformation is presently causing structural changes
Tertiary
Geological age from about 65 to 2 million years ago
Tertiary recovery
Oil generated by a method other than pressure release or depletion (primary), or the injection of water (secondary)
Thermocline
The ocean phenomenon characterised by a sharp change in temperature with depth
Thermohaline
The vertical overturning of water masses due to seasonal heating, evaporation, and cooling
Tracer
A chemical compound or isotope added in small quantities to trace flow patterns
Transfer of responsibility
Transfer of all rights and obligations associated with a storage site to a designated authority; will normally be granted when the obligations in the site closure permit has been met with an adequate level of confidence
Trap
(geology) A geological structure that physically retains fluids that are lighter than the background fluids, e.g. a convex fold
Trapping
(CO2) Containment or immobilisation of CO2, there are four main trapping mechanisms: structural or stratigraphic trapping; residual CO2 trapping (capillary trapping) by capillary forces; solubility trapping by dissolution of CO2 in resident formation fluids forming a non-buoyant fluid; and mineral trapping where CO2 is absorbed by solid minerals present in the storage volume
Triple point
The temperature and pressure where carbon dioxide exists as a gas, liquid and solid simultaneously
Ultramafic rocks
An igneous rock consisting almost entirely of iron- and magnesium-rich minerals with a silica content typically less than 45%
Under-saturated
A solution that could contain more solute than is presently dissolved in it
UNFCCC
United Nations Framework Convention on Climate Change, which was adopted at New York on 9 May 1992
Unminable
Extremely unlikely to be mined under current or foreseeable economic conditions
Updip
Inclining upwards following a structural contour of strata
Upper ocean
The ocean above 1000m depth
UTM
Universal Transverse Mercator geographic coordinate system
Vadose zone
Near surface layer of aeration above the water table (where ambient air infiltrates soil)
Validation
(in the context of CDM) The process of the independent evaluation of a project by a designated operational entity on the basis of set requirements
Ventilation
The exchange of gases dissolved in sea-water with the atmosphere, or genrally, gas exchange between an animal or a man-made space and the environment
Verification
(CO2 storage) The proof, to a standard still to be decided, of the CO2 storage using monitoring results; (in the context of CDM) The independent review by a designated operational entity of monitored reductions in anthropogenic emissions
Vertical seal
Geological structure impeding the movement of fluids vertically (caprock)
Viscous fingering
Flow phenomenon arising from the flow of two largely immiscible fluids through a porous medium
Water column
Vertically continuous mass of water from the surface to the bottom sediments of a water body
Well
Manmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids
Well with multiple completions
Well drilled with multiple branching holes and more than one hole being made ready for use
Wellbore
The physical hole that makes up the well, it can be cased, open, or a combination of both; open means open for fluid migration laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migration
Well-bore annulus
The annulus between the rock and the well casing
Wellhead pressure
Pressure measured on surface at the top of the well
Wettability
Surface with properties allowing water to contact the surface intimately
ZEP
European Technology Platform for Zero Emission Fossil Fuel Power Plants
Zero-carbon energy carrier
Carbon-free energy carrier, typically electricity or hydrogen