Definition depends on jurisdiction. In Canada, abandoned wells have been plugged but where the site has not been fully reclaimed (similar to a plugged well in the United States). In the U.S., abandoned wells are unproductive wells with a known operator but are often confused with orphaned wells. Due to the confusion and multiple definitions, we recommend avoiding use of the term 'abandoned' unless in a specific regulatory context.
The use of technologies and operational practices to directly reduce emissions from oil and natural gas
A site that is actively producing, processing, transporting, or storing at least one product.
- active facility
A facility that is actively processing or handling oil or natural gas
- activity factor (AF)
The population of emitting equipment
. For example, activity factor could refer to the mileage of natural gas
pipeline, the count of thief hatches on a facility or the mechanical power of gas turbines.
- administering organization
The entity responsible for running a voluntary emissions reduction initiative and managing participation.
- aggregated data
Emissions data that has been collected from multiple sources and summarized, usually for the purpose of reporting or statistical analysis.
- Alberta Energy Regulator (AER)
The regulatory body that oversees the development of oil, natural gas
, oil sands, and coal resources in the province of Alberta, Canada.
- Alternative Fugitive Emissions Management Program (alt-FEMP)
Innovative and science-based alternatives to fugitive emissions
management programs (FEMPs). Alternative programs may incorporate the use of various LDAR
technologies such as, unmanned aerial vehicles, vehicle-mounted sensors, and continuous monitoring devices to detect, track, repair, and report fugitive emissions
. This term is used in Western Canada; in the U.S. and elsewhere, the term 'Alternative LDAR
' is often used.
A discernible increase of a measured atmospheric gas over a baseline in which both the discernible increase and baseline are pre-defined. An anomaly
occurs when the atmospheric concentration of a gas becomes larger than the minimum atmospheric concentration of that gas a technology can discern above noise. Not to be confused with detection
Of, relating to, or resulting from the influence of human beings on nature. Source
- associated gas
Sweet or sour natural gas
that is associated with the production of crude oil or crude bitumen. Often referred to as "solution gas", this gas evolves or "breaks out solution" from crude oil or crude bitumen under specific reservoir or production conditions.
- atmospheric tank
A storage tank in which product is stored at ambient pressure. Atmospheric tanks are designed to operate at pressures less than 0.5 psig.
- atmospheric transport modeling
A remote emissions measurement
technique. Downwind mixing ratios of a pollutant, geospatial data (e.g., source height and location), and environmental data (e.g., wind speed and direction) are used to infer the location and/or mass or volumetric flux of a source. Many approaches exist.
- audio, visual, and olfactory (AVO)
The verification of an organization's emissions data, practices, or performance by a third party.
Designed to enable verification of a organization's progress towards a goal or adherence to a voluntary initiative
The release of gas from processing equipment
or pipelines to the atmosphere in order to relieve pressure so that maintenance, testing or other activities can take place.
- bottom-up inventory
A list of emission sources by category and quantity. Often refers to an aggregate emission rate
estimate achieved by multiplying activity factors (counts of components, equipment
, or throughput) by emission factors (estimates of gas-loss rates per unit of activity). Most bottom-up inventories use emission factors derived from industry averages rather than measurements specific to the company. Bottom-up inventory emission rate
estimates are consistently lower than site-level and regional emissions measurements in academic research.
- bottom-up inventory quantification methodology
Documentation of facility specific details, such as facility process operations, production, and emissions calculations used during a reporting period.
- bottom-up measurement
that occurs at a granular scale (e.g., component
) that is used to estamiate emissions more broadly. Bottom-up measurements are often averaged into emissions factors and combined with activity factors to build a bottom-up inventory
- British Columbia Oil and Gas Commission (BCOGC)
The governing body that oversees oil and gas activities within the province of British Columbia, Canada.
- carbon intensity
The ratio of carbon emissions to some measure of productivity, such as natural gas
production or energy content of oil.
- carbon market
A greenhouse gas trading system that enables monetisation of emissions reductions and/or strong performance relative to other market participants. Participants may buy or sell units of GHG
emissions in order to operate within the limits outlined by the agreement governing a particular market.
- carbon offset
A unit of greenhouse gas emissions reduced by one actor that can be traded to compensate for emissions by another actor.
A voluntary initiative
that holds participants to binding
standards that may include emissions reduction performance targets, use of specific technologies, and adoption of methodologies. Certifications entail an explicit declaration of achievement from the administering organization
to the participant.
The chemical reaction where a hydrocarbon
reacts with oxygen to create carbon dioxide, water, and heat. Energy is obtained from fossil fuels through combustion
of the fuel. Source
- combustion efficiency
A voluntary initiative
requiring participants to pledge efforts towards a goal that is decided upon by a governing body or collectively by participants within a group. Commitments are typically auditable
, and focus on achieving future goals.
The work incorporating the steps taken to transform a drilled well into a producing one. These steps include, but are not limited to: casing the well, cementing the casing, perforating the casing, installing down hole flow control or isolation equipment
, hydraulic fracturing, and installing a well head with a production tree.
In emissions attribution, a component
is the smallest scale of oil and gas infrastructure. Examples include valves, flanges, and threaded connections. Multiple components comprise equipment
(e.g., tanks, separators) and a site may have mutliple pieces of equipment
- Comprehensive Monitoring Program
monitoring program that combines screening
methods with close-range methods, to diagnose and precisely pinpoint leaking components.
- continuous measurement
technology installed at a facility to provide repeated emissions measurements at high temporal resolution. Typical continuous measurement
technologies may acquire measurements multiple times per second or multiple times per day.
- controlled release
Intentional releases of methane
at a known location and rate used to test the performance of methane detection
technology. Colorado State University's METEC facility is a well-known testing facility.
- design emissions
A determination that a source may be present. Typically requires on analysis of one or a series of measured anomalies. Detections can be defined in terms of magnitud and/or duration of elevated mixing ratio or emission rate
. For example, a detection
event could be defined as an anomaly
that reaches an estimated mass emission rate
of 5 standard deviations above a 24-hour baseline Unlike an anomoly, a detection
is intended to lead to a further action, e.g., follow-up and/or root-cause analysis.
The process of differentiating a product (typically natural gas
) on the basis of some characteristic (typically a measure of carbon intensity
The act of releasing private information to a target audience.
- disclosure level
A measure of disclosure
for voluntary initiatives introduced in Highwood's Voluntary Initiatives report.
- dispersion modeling
Mathematicaly simulations that predict how a pollutant will move through the atmosphere.
The transportation of refined petroleum products from distribution
hubs to the end users of these products.
The final stage in the oil and gas value chain. Activities include distribution
, retail, marketing, product development, and consumption by the end user.
- emission factor (EF)
A representative value that attempts to relate the quantity of a pollutant released to the atmosphere with an activity associated with the release of that pollutant. These factors are usually expressed as the weight of a pollutant, divided by a unit weight, volume, distance, or duration of the activity emitting the pollutant (e.g., kilograms of particulate emitted per megagram of coal burned). Such factors facilitate an estimation of emissions from various sources of air pollution. In most cases, these factors are simply averages of all available data of acceptable quality, and are(...)
- emission rate
A measure of how quickly a pollutant is being introduced to the atmosphere. Typically expressed in either mass per unit time (e.g., kg/hr) or volume per unit time (e.g., SCF/hr). Many units exist and are used. To easily convert among them, try out Highwood's conversion tool, How Much Gas is That?!
- emission trading system (ETS)
Market-based instruments that create incentives to reduce emissions where these are most cost-effective. In most regulatory trading systems, the government sets an emissions cap in one or more sectors, and the entities that are covered are allowed to trade emissions permits. Rapid growth of voluntary ETSs is also underway. Source
- emissions inventory
A list of an organziation's emissions sources and their magnitude, which may be estimated using emissions factors, engineering estimates, measurement
, or a combination.
- engineering solution
A solution to a problem or difficult situation that relies on the application of math and science
- Environmental Protection Agency (EPA)
A United States government agency whose work it is to improve society’s understanding of climate change and its impacts on human health and the environment. The data, tools, and resources that EPA
develops can also be used by other agencies, organizations, states, tribes, and communities to help tackle the climate crisis effectively, equitably, and sustainably. Source
In emissions attribution, equipment
is the second most granular piece of oil and gas infrastructure. Examples include tanks and separators. See definition of component
for more details.
The concept that two LDAR
programs mitigate equal amounts of emissions. In the context of LDAR
programs, alternative work practices and technologies are required to demonstrate that they meet or exceed mitigated emissions under regulatory frameworks and voluntary initiatives (e.g., MiQ).
see: Environmental, Social, and Governance
- fixed sensor
An intentional, controlled burning of natural gas
that takes place during production and processing. Gas is ignited at the top of a flare stack, creating a characteristic flame. Source
Venting that occurs in a storage tank when the pressure of liquid with entrained gas drops and lighter compounds dissolved in the liquid are released/vented off.
- follow-up survey
An inspection to confirm or deny potential leaks detected during screening
. Typically, a screening
technology will identify a potential leak
at the site or equipment
-scale. Follow-up surveys diagnose leaks at the component
scale, typically with handheld detection
- fugitive emissions
The unintentional release of hydrocarbons to the atmosphere. Often referred to as leaks. Source
- Fugitive Emissions Management Program (FEMP)
A program that is intended to complement a duty holder’s overall emissions reduction strategy by establishing a plan and supporting systems to systematically detect and manage fugitive emissions
. This plan includes the systematic detection
and repair of leaks, malfunctioning equipment
, and surface casing vent flows. Detection
of these leaks relies on regular surveys or screenings of sites for fugitive emissions
. The term FEMP is characteristic of Western Canada. In the U.S. and elsewhere, the term 'LDAR Program
' is often used.
Source | Source 2
The collection of petroleum products from their extraction point (wells), and their transport to a processing facility. A typical gathering
system is highly branched, and consists of small-medium diameter pipelines with medium operating pressures.
- Gaussian plume model
- GHG Protocol
An emissions quantification
framework that is widely used by businesses, industry associations, NGOs, and other organizations. Some initiatives use the GHG Protocol
for their emissions quantification
requirements. GHG protocol
has published several standards but is recognized for these two emission quantification
guidelines: (1) Corporate Standard – for scope 1, 2, and energy-related scope 3, and (2) Corporate Value Chain (Scope 3) Standard – for life-cycle emissions, both upstream
- Global Warming Potential (GWP)
was developed to allow comparisons of the global warming impacts of different gases. Specifically, it is a measure of how much energy the emissions of 1 ton of a gas will absorb over a given period of time, relative to the emissions of 1 ton of carbon dioxide (CO2). The larger the GWP
, the more that a given gas warms the Earth compared to CO2 over that time period. The time period typically used for GWPs is 100 years. GWPs provide a common unit of measure, which allows analysts to add up emissions estimates of different gases (e.g., to compile a national GHG
inventory), and allows(...)
- greenhouse gas (GHG)
A gas that traps heat in the atmosphere, such as carbon dioxide, methane
, nitrous oxide, and fluorinated gases. Source
A set of frameworks, standards, principles, and/or tools designed to assist participants in meeting their goals and reporting on their progress
- handheld instrument
- heavy-tailed distribution
A highly skewed probability distribution
. Most emissions distributions are heavy-tailed, with a small number of super-emitters accounting for the majority of emissions.
- hot tap
The ability to safely tie into a pressurized system (e.g., pipeline, process piping, pressure vessels, etc.) by drilling or cutting into it while it is on stream and under pressure
A naturally occurring organic compound comprising hydrogen and carbon. Hydrocarbons can be as simple as methane
[CH4], but many are highly complex molecules, and can occur as gases, liquids or solids. The molecules can have the shape of chains, branching chains, rings or other structures. Petroleum is a complex mixture of hydrocarbons. The most common hydrocarbons are natural gas
, oil and coal. Source
A site that is not actively producing, processing, transporting, or storing a product.
- incomplete combustion
- instrument air
Air that is used to supply pneumatic devices.
- instrument gas
- LDAR method
The combination of an LDAQ technology, a work practice, and analytics for use in an LDAR program
. An LDAQ method must clearly state any mandatory actions to be performed as part of the work practice, along with suitable operating conditions for the technology. These can include environmental conditions, limitations on facility types, technology configurations, and survey procedure. Source
- LDAR program
The systematic implementation of one or more LDAQ methods across a collection of assets. The program describes the method, or combination of methods, to be used for each facility, along with survey frequency, repair response, and reporting standards. Ultimately, it is the LDAR program
that results in emissions mitigation
, not the technologies or methods in isolation. Source
An open-source modeling framework for exploring the effectiveness of methane leak detection
programs. The purpose of LDAR-Sim
is to enable transparent, collaborative, flexible, and intuitive investigation of emerging LDAR
technologies, methods, work practices, regulations, and deployment strategies. Learn more here.
- LDAR technology
A gas sensing instrument, optionally configured with a deployment platform and/or ancillary instruments (e.g. anemometers, positioning), that can be used to gather data on emissions. Source
- leak detection and repair (LDAR)
and Repair is a work practice designed to identify leaking equipment
so that emissions can be reduced through repairs. A component
that is subject to LDAR
requirements must be monitored at specified, regular intervals to determine whether or not it is leaking. Any leaking component
must then be repaired or replaced within a specified time frame. Source
- leak-size distribution
rates for a group of sources. Leak
-size distributions are often heavy-tailed, with a small number of large sources accounting for most emissions.
- lifecycle analysis
A technique for assessing the environmental aspects associated with a product over its life cycle. Source
- liquified natural gas
that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport
Acquiring emissions data directly from the environment at a specific place and time.
A colourless, odourless gas that occurs abundantly in nature and as a product of certain human activities. Methane
is the simplest member of the paraffin series of hydrocarbons and is among the most potent of the greenhouse gases. Its chemical formula is CH4. Source
- methane slip
Uncombusted fuel that passes through an engine.
A term referring to a stage in the oil and gas value chain following production and preceding distribution
. Activities include processing, pipeline transportation, refining and storage.
- minimum detection limit
The amount that emissions are reduced below a baseline.
- national inventory report (NIR)
At its eighth session, the Conference of the Parties (COP), the decision-making body responsible for monitoring and reviewing the implementation of the United Nations Framework Convention on Climate Change, requested the secretariat to publish on its website the annual inventory submissions consisting of the national inventory report (NIR)
and common reporting format (CRF) of all Parties included in Annex I to the Convention. The NIRs contain detailed descriptive and numerical information and the CRF tables contain all greenhouse gas (GHG)
emissions and removals, implied emission(...)
- natural gas
is a naturally occurring and flammable hydrocarbon
gas that is used for fuel. Its primary component
, but it can also contain ethane, propane, butane, and pentanes. Often, impurities including oxygen, hydrogen sulfide (H2S), nitrogen, water, and carbon dioxide (CO2) are also present.
- net zero
Achieving a state where either (1) no greenhouse gases are emitted, or (2) remaining emissions are offset through other actions or technologies that remove carbon from the atmosphere.
- nonroutine venting
Upset, emergency, or intermittent venting of hydrocarbon
emissions. This could include emergency process evacuation events.
- Oil and Gas Climate Initiative (OGCI)
A CEO-led initiative that aims to accelerate the industry response to climate change. OGCI member companies explicitly support the Paris Agreement and its aims. Source
- Oil & Gas Methane Partnership (OGMP)
A Climate and Clean Air Coalition initiative led by the UN Environment Programme, in partnership with the European Commission, the UK Government, the Environmental Defense Fund, and leading oil and gas companies. Source
- optical gas imaging (OGI)
A common leak detection
approach that uses thermal infrared cameras to visualize methane
and various other organic gases. Common OGI cameras create images of a narrow range of the mid-IR spectrum (3.2− 3.4 μm wavelength) which methane
and other light hydrocarbons actively absorb.
A site with no known owner. Often occurs when companies go bankrupt.
- other test method 33A (OTM 33A)
OTM 33A uses fast response instruments mounted on ground-based vehicles for the geospatial measurement
of air pollution (GMAP) near the driving route. Typically, the vehicle remains stationary for an extended period of time as the methane plume
washes over it. Location and source emission rate
are estimated. Source
- performance metric
A permanently inactive well that has been filled with cement.
- pneumatic controller
Pneumatic controllers are a type of pneumatic instrument
used on oil and gas sites. They control conditions such as temperature, pressure, and fluid levels. Source
- pneumatic instrument
powered through pressurized gas (either air or natural gas
). They are frequently used when there is no electricity available on a site, and are a known source of methane
emissions. Pneumatic instruments are often designed to vent gas with every cycle of their operation, referred to as "bleeding". Source
- pneumatic pump
Pneumatic pumps are a type of pneumatic instrument
. They are used to inject chemicals (such as methanol) into wells and pipelines, or circulate fluids. Source
- pressure relief valve
A pressure relief valve
(PRV) is a safety mechanism used to help regulate the pressure in a system. Pressure relief valves are a leading cause of emissions from hydrocarbon
storage tanks. As the pressure in these tanks rises, the valve may open, releasing pressure, and in turn, releasing natural gas
into the atmosphere. In this sense, PRVs are a source of venting.
- pressure safety valve
- probability of detection
The probability that a given emission source will be detected by an LDAR method
. Probability of detection
is often depicted as a sigmoid curve or surface, where it is the function of emission rate
and other relevant variables (e.g., wind speed).
A general term for characterizing emissions numerically. Can be with emission factor bottom-up inventories or based on measurement
. With measurement
it often referes to emission rate
estimation, but atmospheric mixing ratios may also be quantified.
- quantitative optical gas imaging (QOGI)
Combines optical gas imaging (OGI)
camera technology with cross-section pixel absorption algorithms to quantify emissions. The brightness of each pixel seen through the OGI camera is proportional to the amount of infrared radiation incident on the camera along the corresponding line of sight through the plume
. The brightness is converted to a concentration and combined with estimated velocities to obtain mass fluxes. Source
A site that has been fully reclaimed, including any wells plugged, topsoil replaced if needed, and vegetation re-established.
Greenhouse gas emissions can be estimated using emissions factors, measurements, or engineering equations at various spatial and temporal scales. Reconciliation
explores whether and why different estimation approaches vary. In some cases, reconciliation
can be defined as a methodology for combining multiple different estimates into a single stronger estimate.
The process by which soil contaminants are managed and removed, and the site is readied for reclamation. In Alberta, this is done following AER
and AEP requirements. Contaminated soil may be hauled to a landfill and then replaced with clean soil, or may be treated onsite until it meets AEP guidelines. Source
- routine venting
- Scope 1, 2, and 3 emissions
Scope 1 or direct emissions are those emissions arising from sources owned or controlled by an organization within a defined boundary. Scope 2 emissions are indirect emissions from the generation of purchased energy, from a utility provider. Scope 3 emissions are all indirect emissions – not included in scope 2 – that occur in the value chain of the reporting company, including both upstream
methods are used to rapidly flag high-emitting sites to direct close-range follow-up source diagnosis and root cause analysis. An example of a common screening
method is an aerial monitoring campaign.
Vessel used for separating a well stream into gaseous and liquid components
An uncharacteristically large point source of methane
. Given that most methane
emissions distributions are heavily skewed, a small number of super-emitters can account for the majority of aggregate emissions across the supply chain. Emissions distributions vary widely by basin and production type, so there is some debate over what constitutes a super-emitter
. Highwood defines a super-emitter
as any emission even with mass flux rate that exceeds 10 kg/h methane
and an ultra-emitter
as any source above 100 kg/h .
- surface casing vent flow (SCVF)
A condition where fluid or gas is flowing from the surface casing vent assembly. This term is typically used in conjunction with land wells. Source
An inactive site that may be brought back online (i.e., it is not plugged).
- Technology Innovation and Emissions Reduction Regulation
The Technology Innovation and Emissions Reduction Regulation
requires regulated facilities to reduce greenhouse gas emissions. The regulation applies to facilities which emit more than 100,000 tonnes of carbon dioxide. Facilities which emit less than the threshold may opt-in to the regulation, and conventional oil and gas facilities under the same ownership may be combined into a single aggregate facility. The regulation sets out high-performance benchmarks or enables the director to set facility-specific product benchmarks. To meet the emissions reduction requirement, facilities can(...)
- The Intergovernmental Panel on Climate Change (IPCC)
The United Nations body for assessing the science related to climate change. It was created to provide policymakers with regular scientific assessments on climate change, its implications and potential future risks, as well as to put forward adaptation and mitigation
- thief hatch
An aperture in a tank or vessel that may be open or closed. They are typically used on low pressure tanks. Thief hatches that have been left open can be a significant source of fugitive emissions
- top-down measurements
The transportation of petroleum products from processing facilities to distribution
systems consist of large-diameter, high-pressure pipelines that transport high volumes of petroleum products across large distances.
The degree to which an initiative or producer discloses their internal operations and standards and allows for accessibility of information regarding an initiative.
The TROPOspheric Monitoring Instrument (TROPOMI
) is the gas-sensing instrument on the Copernicus Sentinel-5 Precursor satellite developed by the European Space Agency. TROPOMI
has been used to identify methane
ultra-emitters around the world.
see: unmanned aerial vehicle
- unconventional oil and gas
Unconventional resources are hydrocarbon
-bearing units where the permeability and porosity are so low that the resource cannot be extracted economically through a vertical well bore and instead required a horizontal well bore followed by multistage hydraulic fracturing to achieve economic production. Source
A term that refers to the exploration and production processes within the oil and gas value chain. Activities include drilling, infrastructure development and production.
- vapor recovery unit (VRU)
A system composed of a scrubber, a compressor, and a switch. Its main purpose is to recover vapors formed inside completely sealed crude oil or condensate tanks. The switch detects pressure variations inside the tanks and turns the compressor on and off. The vapors are sucked through a scrubber, where the liquid trapped is returned to the liquid pipeline system or to the tanks, and the vapor recovered is pumped into gas lines. Source
- vented emissions
- voluntary initiative
A coordinated effort managed by an administering organization
that enables participants to take standardized voluntary steps towards targeting, achieving, and/or taking credit for emissions reductions.