Highwood’s Glossary

Terminology for greenhouse gas emissions management in the oil and gas industry can be confusing and inconsistent. The Highwood Glossary proposes a standard set of terms and definitions to help industry, regulators, innovators, and academics in different parts of the world speak the same language.

AJAX progress indicator
  • abandoned
    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.
  • abatement
    The use of technologies and operational practices to directly reduce emissions from oil and natural gas systems.
  • active
    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 fluid streams
  • active remote imaging
    Measures methane by emitting an energy source with a specific wavelength and measure signal intensity reduction due to absorption.
  • activity factor (AF)
    A population of emitting equipment that can be multiplied by an emission factor to estimate emissions volume or mass over time. Examples of common activity factors include the mileage of natural gas pipeline, the count of thief hatches on a facility, the mechanical power of gas turbines, or other parameters that directly influence the rate of operation (e.g., engine operating hours).
  • administering organization
    The entity responsible for running a voluntary emissions reduction initiative and managing participation.
  • AER
  • AF
  • aggregated data
    Emissions data collected from multiple sources and combined, usually for 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.
  • alt-FEMP
  • 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.
  • anomaly
    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.
  • anthropogenic
    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", associated gas breaks out of 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.
  • attribution
    Determination of the emission source category associated with a detection event.
  • audio, visual, and olfactory (AVO)
    Audio, visual, and olfactory (AVO) is a methane detection survey performed using human senses. Regulations often have some form of AVO requirement that is equipment or site specific.
  • audit
    The verification of an organization's emissions data, practices, or performance by a third party.
  • auditable
    Designed to enable verification of a organization's progress toward a goal or adherence to a voluntary initiative or regulation.
  • AVO
  • binding
    A voluntary initiative that incorporates compliance measures.
  • blowdown
    The purposeful venting of natural gas to the atmosphere during well operations and/or during pipeline operations or maintenance to relieve pressure in the pipe.
  • bottom-up emissions inventory
    A list of emission sources by category and quantity and aggregated into overall estimates that could be by site, business unit, and/or company over a specified period of time (typically a reporting year). Bottom-up inventories can use generic emission factors derived from industry averages, company-specific factors, direct measurement, engineering calculations, or manufacturer data.
  • 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
    A measurement that occurs at a granular scale (e.g., component) used to estimate emissions more broadly. Bottom-up measurements can be averaged into emission 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 monetization 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.
  • certification
    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.
  • CMP
  • combustion
    The chemical reaction where a hydrocarbon reacts with oxygen to create heat and oxides such as carbon dioxide and water. Energy is obtained from fossil fuels through combustion of the fuel.  Source
  • combustion efficiency
    How efficeintly a piece of equipment is burning a fuel. Combustion efficiency is an important consideration when estimating emissions, since combustion of natural gas destroys methane and creates carbon dioxide, which has a lower greenhouse potential. Higher combustion efficiencies will result in a higher degree of methane destruction and lower overall carbon intensity.
  • combustion slip
    Methane emissions resulting from incomplete combustion of natural gas by an engine.
  • commitment
    voluntary initiative requiring participants to pledge efforts toward a goal that is decided upon by a governing body or collectively by participants within a group. Commitments are typically auditablebinding, and focus on achieving future goals.
  • completion
    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.
  • component
    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 multiple pieces of equipment or equipment groups.
  • comprehensive monitoring program
    A methane monitoring program that combines screening methods with close-range methods to diagnose and precisely pinpoint leaking components.
  • continuous measurement
    Methane detection 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.
  • continuous monitoring
    Methane detection technology installed at a facility, on or near equipment with the potential to emit, that monitors for methane emissions on an ongoing basis.
  • controlled release
    Intentional releases of methane at a known location and rate used to test the performance of methane detection and quantification technology. Colorado State University's METEC facility is a well-known testing facility.
  • cost of mitigation
    A metric (usually $/tonne of CO2 equivalent) that enables apples-to-apples comparison of emission reduction opportunities.
  • design emissions
    Emissions associated with a piece of equipment or facility under normal operations (operating within design parameters). Includes vented emissions and emissions from incomplete combustion.
  • detection
    A determination by a method or device that methane levels are above ambient background concentration and that a source may be present. Typically requires an analysis of one or a series of measured anomalies. Detections are often defined in terms of magnitude and/or duration of elevated mixing ratio. For example, a detection event could be defined as an anomaly that reaches an estimated mixing ratio of 3 standard deviations above a 24-hour baseline.
  • differentiation
    The process of differentiating a product (typically natural gas) on the basis of some characteristic (typically a measure of carbon intensity or ESG performance).
  • disclosure
    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
    Mathematical simulations that predict how a pollutant will move through the atmosphere.
  • distribution
    The segment of the natural gas value chain comprised of pipelines and metering and regulating equipment, used to deliver natural gas to end-use consumers.
  • downstream
    The final stage in the oil and gas value chain. Activities include distribution, retail, marketing, product development, and consumption by the end user.
  • drone
    A flying vehicle with no human on board, either automated or remotely operated (i.e., UAV).
  • ECCC
    Environment and Climate Change Canada.
  • emission factor (EF)
    A value that describes typical mass or volume of methane emissions per unit of activity. Emission factors can be generic or company specific. Source
  • 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 air pollutants discharged into the atmosphere over a period, typically a year. Inventories can exist for a variety of entities, including companies, industry groups (e.g., OGCI, ONE Future), basins, and countries. Inventories are often broken into source categories, which may be general (e.g., venting versus fugitives) or granular (e.g., high-bleed versus low-bleed pneumatics).
  • 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
  • Environmental, Social, and Governance (ESG)
    Refers to a collection of corporate performance evaluation criteria that assess the robustness of a company’s governance mechanisms and its ability to effectively manage its environmental and social impacts. Examples of ESG data include the quantification of a company’s carbon emissions, water consumption or customer privacy breaches. Institutional investors, stock exchanges and boards increasingly use sustainability and social responsibility disclosure information to explore the relationship between a company’s management of ESG risk factors and its business performance. Source
  • EPA
  • equipment
    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.
  • equivalence
    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).
  • ESG
    see: Environmental, Social, and Governance.
  • ETS
  • fixed sensor
    A permanently installed emissions monitoring system. See continuous measurement.
  • flaring
    An intentional, controlled burning of natural gas. Gas is ignited at the top of a flare stack, creating a characteristic flame. Source
  • flashing
    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 through a screening survey. Typically, 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 methods.
  • fugitive emissions
    Unintentional methane and/or other hydrocarbon emissions. Examples include leaks, process upsets, and emissions from human error, such as leaving a thief hatch open on a storage vessel. 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
  • gas capture
    Re-routing natural-gas which would otherwise be vented to the atmosphere.
  • gathering
    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
    The most commonly used dispersion model (see dispersion modeling). The Gaussian plume model is a relatively simple model (conceptually and computationally) that assumes the plume follows a normal (Gaussian) distribution in 3 dimensions.
  • GHG
  • 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 and downstream.
  • Global Warming Potential (GWP)
    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. Because different GHGs break down in the atmosphere at different rates, the time period frequently used to calculate GWPs is 100 years. GWPs provide a common unit of measure, which allows analysts to add up emissions(...)
  • GMI
    see: Global Methane Initiative
  • greenhouse gas (GHG)
    A gas that traps heat in the atmosphere, such as carbon dioxide, methane, nitrous oxide, and fluorinated gases. Source
  • guideline
    A set of frameworks, standards, principles, and/or tools designed to assist participants in meeting their goals and reporting on their progress
  • GWP
  • handheld instrument
    A small, portable methane detection instrument that is often used to detect and diagnose leaks at the component scale. Examples include optical gas imaging (OGI) cameras and handheld organic vapour analyzers (OVAs).
  • 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
  • hydrocarbon
    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
  • inactive
    A site that is not actively producing, processing, transporting, or storing a product.
  • incomplete combustion
    Natural gas fuel not combusted by an engine or flare. Incomplete combustion increases carbon intensity because methane has a higher GWP than carbon dioxide.
  • instrument air
    Air that is used to supply pneumatic devices.
  • instrument gas
    Natural gas that is used to supply pneumatic devices.
  • LCA
  • LDAR
  • LDAR method
  • LDAR program
    The process for identifying leaking equipment and conducting repairs. Includes the systematic implementation of one or more methane detection methods across a collection of assets. The program includes the method, or combination of methods, to be used for each facility, along with survey frequency, repair response, and reporting requirements. Regulations often mandate LDAR, and components subject to LDAR must be monitored at specified, regular intervals. Source
  • LDAR-Sim
    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
    A type of fugitive emission in which hydrocarbons are unintentionally released to the atmosphere due to equipment failure. Most leaks come from failed valves and connections. Source
  • leak detection and repair (LDAR)
    Leak Detection 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
    A distribution of leak 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
  • liquid unloading
    Removal of accumulated fluids from well bore either by venting (“blowing down”) or using artificial lift techniques (e.g., plunger lifts).
  • Liquified Natural Gas (LNG)
    Natural gas that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport.
  • LNG
    see: liquified natural gas
  • localization
    Identifying the physical location of a leak source. Localization can be done at different scales (site-level, equipment-level and component-level).
  • MACC
    A Marginal Abatement Cost Curve is a graphical representation of the emissions abatement potential of different mitigation options and their corresponding abatement costs.
  • measurement
    A general term for acquiring empirical emissions data from the environment.
  • measurement-informed inventory (MII)
    An emissions inventory that incorporates company-specific measurements and that does not rely exclusively on generic assumptions. Various regulatory and non-regulatory approaches exist for developing MIIs that differ in their requirements. Examples include OGMP 2.0, Veritas Protocols, the MiQ Standard, and Colorado’s GHG Intensity Rule. Most MIIs do not require exclusive use of measurements but encourage operators to minimize user of generic inputs.
  • Measurement Monitoring, Reporting, Verification (MMRV)
    Measurement, Monitoring, Reporting and Verification (MMRV) is a multi-step process used to account for the greenhouse gas (GHG) emissions and emissions intensity across the supply chain.
    The Methane Emissions Technology Evaluation Center (referred to as METEC) is a test and research facility for emissions leak detection and quantification (LDAQ) technology development, field demonstration, hands-on LDAQ equipment training, and protocol and best practices development. The METEC facility is operated by the Energy Institute at Colorado State University (CSU) and is located on CSU’s foothills campus.
  • methane
    A colorless, odorless gas that occurs abundantly in nature and as a product of certain human activities. Its chemical formula is CH4. Source
  • methane intensity
    The amount of methane emitted divided by some measure of productivity, such as methane produced, volume of gas sent to sales, or amount of produced energy.
  • methane monitoring method
    The combination of a methane monitoring technology, a work practice, and analytics, for use in an LDAR program. A methane monitoring 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 (i.e., LDAR method).
  • methane monitoring technology
    The process for identifying leaking equipment and conducting repairs. Includes the systematic implementation of one or more methane detection methods across a collection of assets. The program includes the method, or combination of methods, to be used for each facility, along with survey frequency, repair response, and reporting requirements. Regulations often mandate LDAR, and components subject to LDAR must be monitored at specified, regular intervals. Source
  • methane slip
    Uncombusted fuel that passes through an engine.
  • midstream
    The segment in the oil and gas value chain that falls between upstream and downstream. Activities include transmission and storage.
  • Minimum Detection Limit (MDL)
    The smallest atmospheric concentration or emission rate that a measurement method is capable of discerning. Probability of detection is a preferred concept because sensitivity depends on context and detection is more likely under a range of favorable conditions.
  • MiQ
    An independent not-for-profit methane certification program established by RMI and SYSTEMIQ to facilitate a rapid reduction in methane emissions from the oil and gas sector.
  • mitigation
    The amount that emissions are reduced below a baseline.
  • mixing ratio
    The proportion of air that is methane, usually in parts per million (ppm) or billion (ppb). Can be for a point, a line (ppm-m), or a 3D area (e.g., column averages).
  • 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
    Natural gas is a naturally occurring and flammable hydrocarbon gas that is used for fuel. Its primary component is methane, but it can also contain ethane, propane, butane, and pentanes. Impurities including oxygen, hydrogen sulfide (H2S), nitrogen, water, and carbon dioxide (CO2) are often 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.
  • nonroutine venting
    Upset, emergency, or intermittent venting of hydrocarbon emissions. This could include emergency process evacuation events.
  • OGMP 2.0
    The Oil & Gas Methane Partnership 2.0 (OGMP 2.0) is the flagship oil and gas reporting and mitigation programme of the United Nations Environment Programme (UNEP). It is the only comprehensive, methane measurement-based international reporting framework for the sector.
  • 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
  • OOOO
    US oil and gas operational and design requirements to limit VOC emissions. Applies to sources built, modified, or reconstructed after August 23, 2011, and on or before September 18, 2015. OOOO will be displaced by OOOOc when OOOOc takes effect.
  • OOOOa
    US oil and gas operational and design requirements to limit methane and VOC emissions. Applies to sources built, modified, or reconstructed after September 18, 2015, and on or before December 6, 2022. OOOOa will be displaced by OOOOc when OOOOc takes effect.
  • OOOOb
    US oil and gas operational and design requirements to limit methane and VOC emissions. Applies to sources built, modified, or reconstructed after December 6, 2022.
  • OOOOc
    US oil and gas operational and design requirements to limit methane emissions. Applies to sources built, modified, or reconstructed on or before December 6, 2022. When OOOOc takes effect, it will displace OOOO and OOOOa.
  • optical gas imaging (OGI)
    A common leak detection approach that uses infrared (thermal) 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.
  • orphaned
    A site with no known owner. Often occurs when companies go bankrupt.
  • other large release event
    A regulatory reporting emissions source category within EPA’s Subpart-W: Abnormal methane emissions exceeding 100 kg/h, not fully accounted for using existing methods in Subpart-W. This source category, quantified based on measurement data, was added in the 2024 revisions to Subpart-W. This source aligns with the threshold for events under the Super Emitter Program in NSPS OOOOb and EG OOOOc.
  • other test method 33A (OTM 33A)
    EPA 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
  • parametric data
    Operational data and characteristics utilized to inform inventories including production rates, equipment specifications, performance characteristics, gas composition, and process parameters.
  • passive remote imaging
    Measures methane through absorption of electromagnetic energy (typically infrared) naturally emitted by the environment.
  • performance metric
    A quantifiable metric describing an LDAR method's performance. Ideally, performance metrics are constrained with independent, single-blind controlled release testing. The most important performance metric is probability of detection (POD) which is commonly expressed as a probability curve or surface. Many other performance metrics exist, including localization and quantification uncertainty, false positive rate, and more.
  • pigging
    The practice of using pipeline inspection gauges or gadgets, devices generally referred to as pigs or scrapers, to perform various maintenance operations. This is done without stopping the flow of the product in the pipeline.
  • plugged
    A permanently inactive well that has been filled with cement.
  • plume
    A body of one fluid (natural gas/methane) moving through another (ambient air).
  • 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
    Oilfield equipment 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 (PoD)
    The probability that a measurement method will successfully detect the presence of a target species such as methane gas in the atmosphere. It is typically depicted as a sigmoid curve where PoD is a function of emission rate. More complex PoD functions may consider other variables relevant for the measurement method (e.g., wind speed).
  • quantification
    A general term for quantifying emissions. It is often used interchangeably with emission rate estimation, but measuring mixing ratios of a pollutant is also a form of quantification.
  • quantitative optical gas imaging (QOGI)
    Combines optical gas imaging (OGI) camera technology with cross-section pixel absorption algorithms to numerically estimate emissions rates. 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. Accuracy of quantification can be affected by wind, temperature, humidity, visibility, and daylight. Source
  • reclaimed
    A site that has been fully reclaimed, including any wells plugged, topsoil replaced if needed, and vegetation re-established.
  • reconciliation
    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.
  • remediation
    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
    Routine venting refers to the intentional release of natural gas into the atmosphere from oil and natural gas equipment. This equipment includes (but is not limited to): pneumatic devices, glycol dehydrators, compressor seals, casing vents, and atmospheric tanks. Source
  • 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 and downstream emissions.
  • screening
    Screening 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.
  • SCVF
  • separator
    Vessel used for separating a well stream into gaseous and liquid components.
  • Subpart-W
    Owners or operators of facilities that contain petroleum and natural gas systems and emit 25,000 metric tons or more of GHGs per year (expressed as carbon dioxide equivalents) must report GHG data to EPA as prescribed in Subpart W. Owners or operators must collect GHG data, calculate GHG emissions, and follow specified procedures for quality assurance, missing data, recordkeeping, and reporting. Subpart W consists of emission sources in ten segments of the petroleum and natural gas industry.
  • super-emitter
    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 debate over what constitutes a super-emitter. Highwood defines a super-emitter as any emission with mass flux rate that exceeds 100 kg/h methane and an ultra-emitter as any source above 1000 kg/h.
  • Super-Emitter Program
    Framework allowing accredited third parties to report leaks over 100 kg/h to the US EPA. Under the methane Super Emitter Program, third parties may apply to EPA to become certified to send data about large methane “events” to the Agency. The rule establishes requirements for the technology that can be used for methane detection, for owners and operators responsible for reported leaks to investigate, for reporting the results of the investigation back to EPA, and for the Agency to make the notifications public on its website. The Super Emitter Program is directed by OOOOb and OOOOc.
  • 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
  • suspended
    An inactive site that may be brought back online (i.e., it is not plugged).
  • Technology Innovation and Emissions Reduction (TIER) 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 equivalent per year. 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(...)
  • 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 options. Source
  • 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. Source
  • TIER
  • top-down measurements
    An emissions measurement that aggregates multiple potential sources into a single estimate. Top-down measurements may be equipment scale (consisting of multiple components), site level (consisting of all equipment groups on site), or regional (consisting of all sites in a measurement area). See bottom-up measurement.
  • transmission
    Natural gas transmission systems move natural gas from upstream gathering, processing, or storage facilities to distribution systems, large-volume customers, or other storage/processing facilities.
  • transparency
    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.
  • UAV
    see: Unmanned Aerial Vehicle.
  • ultra-emitter
     A large super-emitter that emits at least 100 kg/h methane.
  • Unaccounted for Gases (UFG)
    The difference between gas receipts and gas deliveries, where gas receipts are volumes that enter a pipeline system and gas deliveries are volumes that exit the pipeline system.
  • 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
  • Unmanned Aerial Vehicle (UAV)
    A flying vehicle with no human on board, either automated or remotely operated (see drone).
  • upstream
    The first segment in the oil and gas value chain, consisting of exploration and production processes. Activities include drilling, production, and processing.
  • 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
    The direct release of unburned natural gas or other hydrocarbon vapors into the atmosphere. Unlike fugitive emissions, vented emissions occur by design. Source
  • Veritas
    An open-source methodology designed to help industry combine measurement data with bottom-up inventories into a measurement-informed inventory that quantifies annual methane emissions over a group of sites.
  • voluntary initiative
    A coordinated effort managed by an administering organization that enables participants to take standardized voluntary steps toward targeting, achieving, and/or taking credit for emissions reductions.
  • Waste Emissions Charge (WEC)
    A fee assessed by the US EPA for reported methane emissions above an intensity threshold of 0.05 to 0.2%. The Waste Emissions Charge (WEC) for methane applies to petroleum and natural gas facilities that emit more than 25,000 metric tons of CO2 equivalent per year as reported under Subpart W of the Greenhouse Gas Reporting Program, that exceed statutorily specified waste emissions thresholds set by Congress, and that are not otherwise exempt from the charge. The WEC starts at $900 per metric ton for 2024 reported methane emissions, increasing to $1,200 per metric ton for 2025 emissions,(...)
  • workover
    The process of performing major maintenance or remedial treatments on an oil or gas well. In many cases, workover implies the removal and replacement of the production tubing string after the well has been killed and a workover rig has been placed on location.

Let’s work together on your emissions management and technology challenges.