Terminology

Generic terms

• Accident: event that affects completely and directly humans and environment in a negative manner.
• Impact: an impacting phenomenon that occurs for sure. An impact, as presented and defined through the GEOENVI project, is an unavoidable consequence of the geothermal project. Disturbance and nuisance are inconveniences caused by geothermal activities. For purpose of classification, we identify disturbance and nuisance as an impact.
• Impacting phenomena (or dangerous phenomena) = event that might possibly have damaging consequences over human or environment, resulting from the emergence and occurrence of a critical event linked to geothermal operations
• Life cycle assessment (LCA): Life-cycle assessment is a method to assess environmental impacts associated with all the stages of a product's life from raw material extraction, through materials processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling. This includes operation of the technology/facility/product as well as all upstream processes (i.e., those occurring prior to when the technology/facility/product commences operation) and downstream processes (i.e., those occurring after the useful lifetime of the technology/facility/product), as in the ‘cradle to grave’ approach. LCA aims to compare the full range of environmental damages of any given product, technology, or service
• Risk:  In a given place and time, combination of the probability of occurrence of an event, the stakes and the vulnerability. A risk, as presented and defined through the GEOENVI project, is characterized by an event, more or less predictable, resulting from geothermal operations and generating potential consequences on human and the environment (ecosystems, atmosphere, and underground water).

Environmental issues terminology

• Abandonment (of a well): well abandonment is the last step of a well lifecycle including well plugging, monitoring of the cement plug and testing of efficiency and well head removal. It shall isolate all permeable and prevent contamination of freshwater aquifers and leakage of any wellbore fluids to the surface.
• Aggression or extreme natural event: extreme flooding, storm or landslide and so on that were not anticipated in the building parameters of the geothermal operation. It also includes vandalism.
• Alteration of living conditions: long-term modification of lifestyle with no life-threatening consequences

• Aquifer alteration (including drinking water aquifer): modification of aquifer (chemical, thermal or other).
• Aquifer depletion (including drinking water aquifer): decrease of fluid reserve that jeopardizes resource durability. The aquifer can be used for drinking water or for agriculture or for nothing.
• Binary plant: a geothermal electricity generating plant employing a closed-loop heat exchange system in which the heat of the geothermal fluid (the "primary fluid") is transferred to a lower boiling point fluid (the "secondary" or "working" fluid). The heat causes the second liquid to turn to steam, which is used to drive a generator turbine.
• Binary system: a power generation system used in binary plants.
• Biodiversity alteration: fauna and flora loss or deterioration.
• Biomonitoring: in environmental sciences, any technique that uses the observation of living species to detect changes in the environment; it may involve the analytical determination of some specific parameter (e.g., heavy metals in blood) or simply the observation of appearance/disappearance of certain species or associations.
• Blowout: sudden and uncontrolled eruption of gas or fluid at the surface.
• BOP: Blow Out Preventer, device used to seal well to prevent uncontrolled gas or liquid eruption at the surface. This device is used in the geothermal or oil and gas industries.
• Buildings & infrastructures (consequence on): damage to buildings along public and private buildings including the geothermal power plant.
• Cause: a combination of elements or phases that can trigger an impacting phenomenon  
• Climate change (consequence on): emissions during a geothermal operation that contribute to global climate changes.  
• Chemical underground disturbance: chemical modifications of the aquifers and reservoirs. It includes the targeted aquifer as well as non-targeted aquifers.
• Cogeneration: the process of generating two or more forms of energy from a single energy source. For geothermal plant, cogeneration refers to heat and electricity production.
• Consequence: changes that a project or activity may cause in the environment, including any effect of any such change on ecosystems, human health or resources.

• Construction work: work related to the construction of the surface installations of the geothermal site (e.g. well platforms, geothermal plant, surface planning and layout). Such work can last for a few weeks.  
• Corrosion: the loss of metal due to chemical or electrochemical reactions, which could eventually destroy a structure. Corrosion can occur anywhere in the production system, either in the borehole or in surface lines and equipment.
• Decommissioning: removal process performed on surface equipment before well abandonment. It consists in dismantling and processing all surface installations.
• Degassing: emission of geothermal gas such as H₂S or hydrocarbon gases (CO₂, N₂, etc.) in the atmosphere deliberately or by accident.
• Disturbances from surface operations: generic term that includes different type of disturbance that may affect population, wildlife, resource and activities during surface operations including vibration and noise caused by drilling operations for example or pumps, dust and traffic from engine circulating over the site, or visual impacts.
• Dry steam plant: take high-pressure hot water from deep inside the earth and convert it to steam to drive generator turbines. When the steam cools, it condenses to water and is injected back into the ground to be used again. Most geothermal power plants are flash steam plants.
• Energy and resource consumption: correspond to fuel and material used at the surface by engines working on site for instance and the resulting particulate matter or CO₂ emissions.
• Flash steam plant: use of steam directly from a geothermal reservoir to turn generator turbines. The first geothermal power plant was built in 1904 in Tuscany, Italy, where natural steam erupted from the earth.  
• Galvanic currents: a direct current which stimulates as the current is suddenly applied or suddenly discontinued.  
• Geomechanical disturbance: phenomena that modify the physical properties and characteristics of the rock.
• Geothermal plant: plant that use underground hydrothermal resources at various temperature and depth to produce electricity and/or heat.
• Geothermal loop (primary loop/ secondary loop): the circuit made by fluid circulation. The primary loop contains geothermal fluid. In binary system, a secondary loop contains a second fluid that has a lower boiling point and is used to generate heat or electricity. In flash system, only one loop exists.
• Global warming potential (GWP): an index that measures how much heat a reference greenhouse gas (carbon dioxide) traps in the atmosphere up to a specific time horizon. The GWP represents the combined effect of the differing lengths of time that these gases remain in the atmosphere and their relative effectiveness in absorbing outgoing infrared radiation. The Kyoto Protocol ranks greenhouse gases based on GWPs from single pulse emissions over subsequent 100-year time frames.  
• Greenhouse gases: any gaseous compound in the atmosphere that can absorb infrared radiation, thereby trapping and holding heat in the atmosphere.
• Ground surface deformation: subsidence or uplift of the ground noticeable at surface
• Health, Safety and Environment (HSE): usually used for management of these issues at a workplace.
• Induced seismicity: earthquake caused by anthropic activities such as geothermal activities.
• Interconnection of aquifers and disturbance of non-targeted aquifer: connection between two or more aquifers that may result in aquifer pollution and disturbance by intrusion of mud, inhibitors, fine particles and hot geothermal fluids into non-targeted aquifers.
• Land use: surface implantation of the geothermal plant, including well and transport pipes, that de facto use land (agriculture and farming, tertiary, natural habitat, etc.)
• Leak due to surface installations/operations, explosions: leaks of water, geothermal fluid, heat transfer fluid or chemicals in the surface circuit or surface reservoirs and retention sites
• Life cycle assessment (LCA): Life-cycle assessment is a method to assess environmental impacts associated with all the stages of a product's life from raw material extraction, through materials processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling. This includes operation of the technology/facility/product as well as all upstream processes (i.e., those occurring prior to when the technology/facility/product commences operation) and downstream processes (i.e., those occurring after the useful lifetime of the technology/facility/product), as in the ‘cradle to grave’ approach. LCA aims to compare the full range of environmental damages of any given product, technology, or service.
• Liquid or solid effusion: effusion from wells during drilling and well operations; includes cuttings, mud, underground water, geothermal fluids or other liquid and gases.
• Marine and freshwater pollution: all kind of pollution (chemical, thermal etc.) of shallow to surface water plans (rivers, lake, wetland, etc.), oceans and their related ecosystems (corals and all flora and fauna present over the ocean floor).
• Microseismicity: refers to seismic events that are detected by seismometers but are not felt by population, events below magnitude 2.0-3.0, depending on many factors including subject sensibility.
• Non-condensable gases (NCG): the gases that do not condense at the same pressure and temperature conditions as water vapor but remain in the gas phase. 
• Naturally Occurring Radioactive Materials (NORM): materials, usually industrial wastes or by-products enriched with radioactive elements found in the environment. In some case, geothermal scaling can contain radionuclides, such as uranium, thorium and potassium and any of their decay products
• Organic Rankine cycle (ORC): a thermodynamic cycle that uses an organic fluid as the working fluid (secondary fluid) in a closed loop for electricity generation. It can utilize low-temperature geothermal heat as commonly done in geothermal binary power plants.

• Ozone depletion potential: a concept that was defined to describe the relative amount of degradation that a chemical compound can cause to the ozone layer.
• Psychological impact: long and short term. May be caused by explosions, induced seismicity, visual and noise disturbances etc.
• Particulate matter: diesel fuel, dust etc.
• Pressure and flow changes in reservoir: it concerns the changes in pressure and flow of the targeted aquifer (i.e. hydro-mechanical modifications). This is the case with simple well operation (no reinjection) or partial reinjection of geothermal fluid or low permeability reservoirs.
• Primary loop: the loop where the primary fluid (e.g. geothermal fluid) flows in a binary plant.
• Resource consumption: energy, water, material used during the life cycle project
• Radioactivity: spontaneous transformation of unstable atoms, called radionuclides that release particles and energy in the form of radiation. In geothermal water, some natural radioactivity is sometimes present.
• Reinjection: underground injection of geothermal fluids, cooled after heat extraction, typically close by the extraction area.  
• Scaling: accumulation of deposit inside the installation (pipes, heat exchangers…), as well as in wells, formed by thermodynamic or corrosion process of the geothermal fluid
• Secondary loop: the loop where the secondary fluid (working fluid, e.g. an organic fluid) flows in a binary plant.
• Seismometer: instrument that makes a record of seismic waves caused by earthquakes and other Earth-shaking phenomena. This record is proportional to the motion of the seismometer mass relative to the earth, but it can be mathematically converted to a record of the absolute motion of the ground.
• Stimulation: a treatment performed to restore or enhance the productivity of a well. This treatment can be done by injecting water at a certain pressure (hydraulic stimulation), by thermal shock injecting cold water in hot rocks (thermal stimulation), or by dissolving some deposited minerals (chemical stimulation).
• Surface disturbances (noise, vibration, dust, smell, land use and visual, etc.): generic term that includes all type of disturbance of neighbors. Vibration can be caused when drilling or because of acting pumps, noise is important during the drilling phase, the operation and workover, smell can be caused by motor oil, engine or plant operation. The visual impact concerns mostly the drilling bit installed and dust material can be caused by traffic or during ground operations.  
• Surface emission from underground: this category concerns all risks and impacts related to underground operations that have effects at surface. While the source of the phenomena is located underground, the resulting impacts are at surface.
• Surface operations: consist in all operations, from the construction phase, to drilling operations and the utilization of the geothermal resource that have an impact at surface (e.g. implantation of the drill pad, maintenance of the cooling tower or well pumps)
• Thermal infrared imagery (TIR): infrared thermography is equipment or method, which detects infrared energy emitted from object, converts it to temperature, and displays the image of temperature distribution.
• Triggered seismicity: where the stress variation is only a small fraction of the natural tectonic stress field.
• Underground fluid disturbance: concerns all phenomena that can affect the underground fluids. That can concern either the geothermal fluid or other untargeted aquifers that were crossed by the wells.
• Underground water: the water present beneath Earth's surface in soil pore spaces and in the fractures of rock formations.
• Vibro-seismic method (or vibrator): an adjustable mechanical source that delivers vibratory seismic energy to the Earth for acquisition of seismic data. Mounted on large trucks, vibrators use a large oscillating mass in direct contact with the ground to put a range of frequencies into the earth.
• Well design & engineering choices: choices of well design (completion, material, diameter, deviation, etc.) during drilling planned operations according to different parameters such as geology, target reservoir, depth, presence of a shallow aquifer.
• Well testing: pumping or injection in wells and monitoring of pressure and temperature variation for short (few hours) or long period of time (few days) to provide information on the reservoir and its behavior or information on the fluid composition by sampling water.