Gas Seepage
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Gas venting, more specifically known as natural-gas venting or methane venting, is the intentional and controlled release of gases containing
alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in whi ...
hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may b ...
- predominately
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...
- into Earth's atmosphere. It is a widely used method for disposal of unwanted gases which are produced during the extraction of
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...
and
crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...
. Such gases may lack value when they are not recyclable into the production process, have no export route to consumer markets, or are surplus to near-term demand. In cases where the gases have value to the producer, substantial amounts may also be vented from the equipment used for gas collection,
transport Transport (in British English) or transportation (in American English) is the intentional Motion, movement of humans, animals, and cargo, goods from one location to another. Mode of transport, Modes of transport include aviation, air, land tr ...
, and distribution. Gas venting contributes strongly to
climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
. Nevertheless, many individual cases are sufficiently small and dispersed to be deemed "safe" with regard to immediate health hazards. Large and concentrated releases are usually abated with
gas flare A gas flare, alternatively known as a flare stack, flare boom, ground flare, or flare pit, is a gas combustion device used in places such as petroleum refineries, chemical plants and natural gas processing plants, oil or gas extraction sites ha ...
s to produce relatively less-harmful
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
gas. Gas venting and flaring that are performed as routine practices are especially wasteful and may be eliminated in many modern industrial operations, where other low-cost options are available to utilize the gas. Gas venting is not to be confused with similar types of gas release, such as those from: * emergency pressure relief as a method of last resort to prevent equipment damage and safeguard life, or * fugitive gas emissions which are unintentional
gas leaks Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such ...
that occur in coal, oil, and gas operations, such as from
orphan wells Orphan, orphaned, or abandoned wells are oil or gas wells that have been abandoned by fossil fuel extraction industries. These wells may have been deactivated due to becoming uneconomic, failure to transfer ownerships (especially at bankruptcy ...
Gas venting should also not be confused with "gas seepage" from the earth or oceans - either natural or due to human activity.


Oil field practice relating to unwanted gas

Petroleum extraction Petroleum is a fossil fuel that can be drawn from beneath the Earth's surface. Reservoirs of petroleum are formed through the mixture of plants, algae, and sediments in shallow seas under high pressure. Petroleum is mostly recovered from oil d ...
from
oil well An oil well is a drillhole boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas m ...
s, where acquiring crude oil is the primary and sometimes sole financial objective, is generally accompanied by the extraction of substantial amounts of so-called
associated petroleum gas Associated petroleum gas (APG), or associated gas, is a form of natural gas which is found with deposits of petroleum, either dissolved in the oil or as a free "gas cap" above the oil in the reservoir. The gas can be utilized in a number of ways a ...
(i.e. a form of raw
natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...
). Global statistics from year 2012 show that the majority (58%) of this gas was re-injected for storage and to help maintain well pressure, 27% was sent to consumption markets, and the remaining 15% was vented or flared near the well site. 100 million tons of the vented associated gas was combusted in flares worldwide, equal to about 3-4% of all gas produced from oil and gas wells. The flared gas yielded nearly 350 million tons of CO2-equivalent emissions of greenhouse gases, contributing about 1% of the 33 billion tons of
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
(CO2) released from the burning of all
fossil fuels A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geologica ...
. Flare Gas Recovery Systems (FGRS) are being increasingly implemented as a more economically productive alternative to flaring. Preferably, all of the unwanted gas would at least be abated in gas flares, but this has not been achieved in practice. For example, the vented volumes from individual wells are sometimes too small and intermittent, and may present other difficulties (e.g. high concentrations of
contaminant Contamination is the presence of a constituent, impurity, or some other undesirable element that renders something unsuitable, unfit or harmful for the physical body, natural environment, wiktionary:Workplace, workplace, etc. Types of contamina ...
s) that make flaring more technically and economically challenging. Also, gas will continue to
effervesce Effervescence is the escape of gas from an aqueous solution and the foaming or fizzing that results from that release. The word effervescence is derived from the Latin verb ''fervere'' (to boil), preceded by the adverb ''ex''. It has the same l ...
from the crude oil for some time after it is moved into storage tanks at the well site and transported elsewhere. This gas may also be routed to a flare stack, utilized, or designed to escape without mitigation through vents or
pressure regulator A pressure regulator is a valve that controls the pressure of a fluid to a desired value, using negative feedback from the controlled pressure. Regulators are used for gases and liquids, and can be an integral device with a pressure setting, a r ...
s. Global tracking estimates from the
International Energy Agency The International Energy Agency (IEA) is a Paris-based autonomous intergovernmental organization, established in 1974, that provides policy recommendations, analysis and data on the global energy sector. The 31 member countries and 13 associatio ...
(IEA) during year 2019 indicate that an additional 32 million tons of methane were vented without abatement from all petroleum extraction; including onshore conventional oil,
offshore oil Offshore drilling is a mechanical process where a wellbore is drilled below the seabed. It is typically carried out in order to explore for and subsequently extract petroleum that lies in rock formations beneath the seabed. Most commonly, the te ...
,
unconventional oil Unconventional (oil and gas) reservoirs, or unconventional resources (resource plays) are Petroleum geology, accumulations where oil and gas Phase (matter), phases are tightly bound to the rock fabric by strong capillary action, capillary forces, ...
, and downstream oil activities. When including the amount released from incomplete gas flares and fugitive emissions, the estimated total is about 37 million tons. Matthew Johnson, from the Energy and Emissions Research Lab (EER) at
Carleton University Carleton University is an English-language public university, public research university in Ottawa, Ontario, Canada. Founded in 1942 as Carleton College, the institution originally operated as a private, non-denominational evening college to se ...
in Ottawa, Ontario, Canada, said in a December 2023 interview thatcontrary to common beliefsventing, particularly from heavy oil facilities designed for normal operations, is the primary source of methane emissions in the oil and gas industry. Johnson stresses the urgency of swiftly retrofitting oil and gas sites, considering that the associated costs are reasonable, based on various studies. The estimated cost for retrofitting for the total industry in Canada is estimated at $3.3 billion between 2027 and 2040 for implementing both venting and flaring requirements in the . Jonson said that while fossil fuels are not going to be phased out "overnight", "when it comes to methane emissions, we have a solution and we can implement it right now." A 2023 Energy and Emissions Research Lab report discusses challenges in meeting the 2030 methane reduction targets under the Global Methane Pledge, due to uncertainties in emission levels from oil and gas operations. The research, which centers on
Alberta, Canada Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...
the Canadian province with the largest oil and gas-industrypresents a methane inventory for 2021 that exceeds the official federal inventory by 1.5 times. The study underscores that nearly two-thirds of emissionsprimarily stemming from uncontrolled tanks, pneumatics, and unlit flares, result from gas ventingindicating substantial opportunities for mitigation. Notably, methane intensities in Alberta are four times higher than those in neighboring British Columbia, highlighting the necessity for independent monitoring and reporting ensuring the success of emission reduction initiatives. Gas venting in the oil and gas industry has gained attention in Alberta, Canada, particularly in light of proposed legislative changes aimed at reducing methane emissions. Federal Environment Minister
Steven Guilbeault Steven Guilbeault (; born June 9, 1970) is a Canadian politician and activist who has served as Minister of Canadian Identity and Culture since 2025. A member of the Liberal Party of Canada, Liberal Party, Guilbeault has sat as a Member of Par ...
presented a plan during the
2023 United Nations Climate Change Conference The 2023 United Nations Climate Change Conference or Conference of the Parties of the UNFCCC, more commonly known as COP28, was the 28th United Nations Climate Change conference, held from 30 November to 13 December at Expo City, Dubai, Unite ...
in
Dubai Dubai (Help:IPA/English, /duːˈbaɪ/ Help:Pronunciation respelling key, ''doo-BYE''; Modern Standard Arabic, Modern Standard Arabic: ; Emirati Arabic, Emirati Arabic: , Romanization of Arabic, romanized: Help:IPA/English, /diˈbej/) is the Lis ...
, outlining a national cap-and-trade system to curb emissions without hindering production. The proposed framework aims to cap 2030 emissions at 35 to 38 percent below 2019 levels, aligning with the federal government's objective of achieving net-zero carbon emissions in the sector by 2050. Given that the oil and gas industry contributes to 28 percent of Canada's emissions, these proposed changes signal a significant effort to address environmental concerns and combat climate change.


Coal mining and coalbed methane activity

Substantial amounts of methane-rich gas are trapped and
adsorbed Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a f ...
within coal formations, and are unavoidably
desorbed Desorption is the physical process where adsorbed atoms or molecules are released from a surface into the surrounding vacuum or fluid. This occurs when a molecule gains enough energy to overcome the activation barrier and the binding energy that ...
in association with
coal mining Coal mining is the process of resource extraction, extracting coal from the ground or from a mine. Coal is valued for its Energy value of coal, energy content and since the 1880s has been widely used to Electricity generation, generate electr ...
. In some cases of sub-surface mining, a formation is permeated with
borehole A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well), other liquids (such as petr ...
s prior to and/or during extraction work, and the so-called
firedamp Firedamp is any flammable gas found in coal mines, typically coalbed methane. It is particularly found in areas where the coal is bituminous. The gas accumulates in pockets in the coal and adjacent strata and, when they are penetrated, the ...
gases allowed to vent as a safety measure. Also during work, methane enters the ventilation air system at concentrations as high as 1%, and is usually freely exhausted from the mine opening. Such ventilation air methane (VAM) is the largest source of methane from all operating and decommissioned coal mines worldwide. Substantial methane also continues to desorb from coal placed into storage and from abandoned mines. The
U.S. Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent agency of the United States government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it began operation on De ...
projects that by year 2020, global methane releases from coal mines throughout the world will exceed 35 million tons or 800 million tons of CO2-equivalent emissions, and account for 9% of all global
methane emissions Increasing methane emissions are a major contributor to the rising concentration of greenhouse gases in Earth's atmosphere, and are responsible for up to one-third of near-term global heating. During 2019, about 60% (360 million tons) of methane r ...
. China contributes over 50% of the total, followed by the United States (10%) and Russia (7%), and then by Australia, Ukraine, Kazakhstan, and India (3-4% each). About 200 mines across a broad scope of countries had implemented technology by the year 2015 to capture about 3 million tons of methane, either for economic use or for abatement in gas flares or thermal oxidizers. Outcroppings, seams, or formations near the surface are also sometimes permeated with wells to extract and capture the methane, in which event it is classified as a form of
unconventional gas Unconventional (oil and gas) reservoirs, or unconventional resources (resource plays) are accumulations where oil and gas phases are tightly bound to the rock fabric by strong capillary forces, requiring specialized measures for evaluation and ...
. Such coalbed methane capture can reduce the volume of gas seepage that would otherwise occur naturally, while in-turn adding emissions of carbon dioxide once the fuel is utilized elsewhere. Global tracking estimates from the IEA during 2019 suggest that about 40 million tons of methane were released from all activities related to coal mining. This total amount includes all vented, fugitive and seepage emissions.


Gas field and gas pipeline practices

In gas fields, acquiring non-associated petroleum gas (i.e. another form of raw natural gas) is the primary financial objective, and very little is unwanted compared to the gas produced in oil fields or coal mines. The majority of venting emissions instead occur during the
pipeline transport A pipeline is a system of Pipe (fluid conveyance), pipes for long-distance transportation of a liquid or gas, typically to a market area for consumption. The latest data from 2014 gives a total of slightly less than of pipeline in 120 countries ...
to trading & distribution hubs,
refineries A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value. Types of refineries Different types of refineries a ...
, and consumer markets. The
U.S. Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and energy production, the research and development of nuclear power, the military's nuclear we ...
reports that a majority of the venting within U.S. gas industry operations in year 2017 occurred at compressor stations and from pneumatically operated controllers and regulators. Improved maintenance strategies and advanced equipment technologies either exist or are being developed to reduce such venting. Global tracking estimates from the IEA during year 2019 further indicate that about 23 million tons of methane were vented from all gas industry segments, including onshore conventional gas, offshore gas,
unconventional gas Unconventional (oil and gas) reservoirs, or unconventional resources (resource plays) are accumulations where oil and gas phases are tightly bound to the rock fabric by strong capillary forces, requiring specialized measures for evaluation and ...
, and downstream gas activities. When including the amount released from fugitive emissions, the estimated total is about 43 million tons.


Historical context

Associated petroleum and coal mining gases were sometimes considered troublesome, dangerous, low value: a "free" by-product associated with financially more lucrative coal or liquid hydrocarbon recovery that had to be dealt with. The growth of international gas markets, infrastructure and supply chains have done much to change this. It is also becoming more of a standard practice to: * capture and use associated gas to provide local power, and to * reinject re-compressed gas for
oil reservoir A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in Porosity, porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by t ...
pressure maintenance,
secondary recovery Petroleum is a fossil fuel that can be drawn from beneath the Earth's surface. Reservoirs of petroleum are formed through the mixture of plants, algae, and sediments in shallow seas under high pressure. Petroleum is mostly recovered from oil d ...
, and potential later reservoir depressurization once hydrocarbon liquids recovery has been maximized and a gas export infrastructure and market access have been established. Today, it is financially viable to develop even relatively small hydrocarbon reservoirs containing non-associated gas (i.e. with little or no oil) close to a market or export route, as well as large, remote accumulations. Fossil gas was recently promoted by some industry advocates and policy makers as a "bridge fuel" that could yield the least waste, and thus environmental damage and accompanying economic losses, during the transition from finite fossil-fuel reserves to more sustainable sources. However, the actual volumes of methane released cumulatively over the supply chain have a near-term climate warming impact which already rivals, and may grow to exceed, that from using coal and oil.


Environmental impact

Venting and other releases of gaseous hydrocarbons have increased steadily throughout the
industrial age The Industrial Age is a period of history that encompasses the changes in economic and social organization that began around 1760 in Great Britain and later in other countries, characterized chiefly by the replacement of hand tools with power-d ...
alongside the rapid growth in production and consumption of fossil fuels. The International Energy Agency estimates that total annual methane emissions from the oil and gas industry alone rose from about 63 to 82 million tons over years 2000 thru 2019; an average increase of about 1.4% per year. Globally, the IEA estimates that the geologic extraction of coal, crude oil, and natural gas is responsible for 20% of all methane emissions. Other researchers have found evidence that their contribution may be substantially higher; 30% or greater. Methane's atmospheric concentration has nearly doubled over the last century, and is already a factor 2.5 greater than at any point in the last 800,000 years. Methane is a potent warming gas despite its lower abundance compared to atmospheric carbon dioxide. Atmospheric methane is responsible for at least one-quarter and as much as one-third of the changes in
radiative forcing Radiative forcing (or climate forcing) is a concept used to quantify a change to the balance of energy flowing through a planetary atmosphere. Various factors contribute to this change in energy balance, such as concentrations of greenhouse gases ...
that drive near-term
climate warming Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...
. The
ethane Ethane ( , ) is a naturally occurring Organic compound, organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is List of purification methods ...
,
propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...
, and
butane Butane () is an alkane with the formula C4H10. Butane exists as two isomers, ''n''-butane with connectivity and iso-butane with the formula . Both isomers are highly flammable, colorless, easily liquefied gases that quickly vaporize at ro ...
components of natural gas have much shorter atmospheric lifetimes (ranging from about 1 week to 2 months) compared to methane (1-2 decades) and carbon dioxide (1-2 centuries). They consequently do not become well-mixed into the atmosphere and have much lower atmospheric abundances. Nevertheless, their oxidation ultimately leads to the creation of longer-lived carbon compounds that also disturb the atmosphere and the planetary
carbon cycle The carbon cycle is a part of the biogeochemical cycle where carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth. Other major biogeochemical cycles include the nitrogen cycle and the water cycl ...
through a variety of complex pathways.


See also

*
Routine flaring Routine flaring, also known as production flaring, is a method and current practice of disposing of large unwanted amounts of associated petroleum gas (APG) during crude oil extraction. The gas is first separated from the liquids and solids d ...
*
Methane emissions Increasing methane emissions are a major contributor to the rising concentration of greenhouse gases in Earth's atmosphere, and are responsible for up to one-third of near-term global heating. During 2019, about 60% (360 million tons) of methane r ...


References

{{reflist


External links


Flare and Vent Disposal Systems on PetroWikiCoalbed Methane on PetroWiki
Natural gas Methane