Fugitive gas emissions

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Fugitive gas emissions are emissions of gas (typically natural gas, which contains methane) to atmosphere or groundwater [1] which result from oil and gas or coal mining activity. [2] In 2016, these emissions, when converted to their equivalent impact of carbon dioxide, accounted for 5.8% of all global greenhouse gas emissions. [2]

Contents

Most fugitive emissions are the result of loss of well integrity through poorly sealed well casings due to geochemically unstable cement. [3] This allows gas to escape through the well itself (known as surface casing vent flow) or via lateral migration along adjacent geological formations (known as gas migration). [3] Approximately 1-3% of methane leakage cases in unconventional oil and gas wells are caused by imperfect seals and deteriorating cement in wellbores. [3] Some leaks are also the result of leaks in equipment, intentional pressure release practices, or accidental releases during normal transportation, storage, and distribution activities. [4] [5] [6]

Emissions can be measured using either ground-based or airborne techniques. [3] [4] [7] In Canada, the oil and gas industry is thought to be the largest source of greenhouse gas and methane emissions, [8] and approximately 40% of Canada's emissions originate from Alberta. [5] Emissions are largely self-reported by companies. The Alberta Energy Regulator keeps a database on wells releasing fugitive gas emissions in Alberta, [9] and the British Columbia Oil and Gas Commission keeps a database of leaky wells in British Columbia. Testing wells at the time of drilling was not required in British Columbia until 2010, and since then 19% of new wells have reported leakage problems. This number may be a low estimate, as suggested by fieldwork completed by the David Suzuki Foundation. [1] Some studies have shown a range of 6-30% of wells suffer gas leakage. [7] [9] [10] [11]

Canada and Alberta have plans for policies to reduce emissions, which may help combat climate change. [12] [13] Costs related to reducing emissions are very location-dependent and can vary widely. [14] Methane has a greater global warming impact than carbon dioxide, as its radiative force is 120, 86 and 34 times that of carbon dioxide, when considering a 1, 20 and 100 year time frame (including Climate Carbon Feedback [15] [16] [9] Additionally, it leads to increases in carbon dioxide concentration through its oxidation by water vapor. [17]

Sources of emissions

7 most common causes of cement and casing failures leading to fugitive gas emissions from a producing well. The cement plug in the lower portion of the well makes this an example of an abandoned well. Differences between SCVF and GM.png
7 most common causes of cement and casing failures leading to fugitive gas emissions from a producing well. The cement plug in the lower portion of the well makes this an example of an abandoned well.

Fugitive gas emissions can arise as a result of operations in hydrocarbon exploration, such as for natural gas or petroleum.

Often, sources of methane are also sources of ethane, allowing methane emissions to be derived based on ethane emissions and ethane/methane ratios in the atmosphere. This method has given an estimate of increased methane emission from 20 Tg per year in 2008 to 35 Tg per year in 2014. [18] A large portion of methane emissions can be contributed by only a few "super-emitters". [19] The annual ethane emission increase rate in North America between 2009 and 2014 was 3-5%. [18] It has been suggested that 62% of atmospheric ethane originates from leaks associated with natural gas production and transportation operations. [20] It has also been suggested that ethane emissions measured in Europe are affected by hydraulic fracturing and shale gas production operations in North America. [21] Some researchers postulate that leakage problems are more likely to happen in unconventional wells, which are hydraulically fractured, than in conventional wells. [1]

Approximately 40% of methane emissions in Canada occur within Alberta, according to the National Inventory Report. Of the anthropogenic methane emissions in Alberta, 71% are generated by the oil and gas sector. [5] It is estimated that 5% of the wells in Alberta are associated with natural gas leaking or venting. [22] It is also estimated that 11% of all wells drilled in British Columbia, or 2739 wells out of 24599, have reported leakage problems. [1] Some studies have estimated that 6-30% of all wells suffer gas leakage. [7] [9] [10] [11]

Well-specific and processing sources

Sources can include broken or leaky well casings (either at abandoned wells or unused, but not properly abandoned, wells) or lateral migration through the geological formations in the subsurface before being emitted to groundwater or atmosphere. [1] Broken or leaky well casings are often the result of geochemically unstable or brittle cement. [3] One researcher proposes 7 main paths for gas migration and surface casing vent flow: (1) between the cement and adjacent rock formation, (2) between the casing and encompassing cement, (3) between the casing and the cement plug, (4) directly through the cement plug, (5) through the cement between casing and adjacent rock formation, (6) through the cement between linking cavities from the casing side of the cement to the annulus side of the cement, and (7) through shears in the casing or well bore. [4]

Leakage and migration can be caused by hydraulic fracturing, although in many cases the method of fracturing is such that gas is not able to migrate through the well casing. Some studies observe that hydraulic fracturing of horizontal wells does not affect the likelihood of the well suffering from gas migration. [23] It is estimated that approximately 0.6-7.7% of methane emissions produced during the lifetime of a fossil fuel well occur during activities that take place either at the well site or during processing. [4]

Pipeline and distribution sources

Distribution of hydrocarbon products can lead to fugitive emissions caused by leaks in seals of pipes or storage containers, improper storage practices, or transportation accidents. Some leaks may be intentional, in the case of pressure release safety valves. [5] Some emissions may originate from unintentional equipment leaks, such as from flanges or valves. [6] It is estimated that approximately 0.07-10% of methane emissions occur during transportation, storage, and distribution activities. [4]

Detection methods

There are several methods used to detect fugitive gas emissions. Often, measurements are taken at or near the wellheads (via the use of soil gas samples, eddy covariance towers, dynamic flux chambers connected to a greenhouse gas analyzer), [3] but it is also possible to measure emissions using an aircraft with specialized instruments on board. [4] [24] An aircraft survey in northeastern British Columbia indicated emissions emanating from approximately 47% of active wells in the area. [8] The same study suggests that actual methane emissions may be much higher than what is being reported by industry or estimated by government. For small-scale measurement projects, infrared camera leak inspections, well injection tracers, and soil gas sampling may be used. These are typically too labour-intensive to be useful to large oil and gas companies, and often airborne surveys are used instead. [7] Other source identification methods used by industry include carbon isotope analysis of gas samples, noise logs of the production casing, and neutron logs of the cased borehole. [25] Atmospheric measurements through both airborne or ground-based sampling are often limited in sample density due to spatial constraints or sampling duration limitations. [19]

One way of attributing methane to a particular source is taking continuous measurements of the stable carbon isotopic measurements of atmospheric methane (δ13CH4) in the plume of anthropogenic methane sources using a mobile analytical system. Since different types and maturity levels of natural gas have different δ13CH4 signatures, these measurements can be used to determine the origin of methane emissions. Activities related to natural gas emit methane plumes with a range of -41.7 to -49.7 ± 0.7‰ of δ13CH4 signatures. [5]

High rates of methane emissions measured in the atmosphere at a regional scale, often through airborne measurements, may not represent typical leakage rates from natural gas systems. [19]

Reporting and regulating emissions

Illustration of surface casing vent flow and gas migration pathways in the subsurface near a producing well. The cement plug in the lower portion of the well makes this an example of an abandoned well. Surface Casing Vent Flow vs Gas Migration.png
Illustration of surface casing vent flow and gas migration pathways in the subsurface near a producing well. The cement plug in the lower portion of the well makes this an example of an abandoned well.

Policies regulating reporting of fugitive gas emissions vary, and there is often an emphasis on self-reporting by companies. A necessary condition to successfully regulate greenhouse gas (GHG) emissions is the capacity to monitor and quantify the emissions before and after the regulations are in place. [26]

Since 1993, there have been voluntary actions by the oil and gas industry in the United States to adopt new technologies that reduce methane emissions, as well as the commitment to employ best management practices to achieve methane reductions at the sector level. [27] In Alberta, the Alberta Energy Regulator maintains a database of self-reported instances of gas migration and surface casing vent flows at wells in the province. [9]

Reporting of leakage in British Columbia did not start until 1995, when it was required to test wells for leakage upon abandonment. Testing upon drilling of the well was not required in British Columbia until 2010. [1] Among the 4017 wells drilled since 2010 in British Columbia, 19%, or 761 wells, have reported leakage problems. [1] Fieldwork conducted by the David Suzuki Foundation, however, has discovered leaky wells that were not included in the British Columbia Oil and Gas Commission's (BCOGC) database, meaning that the number of leaky wells could be higher than reported. [1] According to the BCOGC, surface casing vent flow is the major cause of leakage in wells at 90.2%, followed by gas migration at 7.1%. Based on the methane leakage rate of the reported 1493 wells that are currently leaking in British Columbia, a total leakage rate of 7070 m3 daily (2.5 million m3 yearly) is estimated, although this number may be underestimated as demonstrated by the fieldwork done by the David Suzuki Foundation. [1]

Bottom-up inventories of leakage involve determining average leakage rates for various emission sources such as equipment, wells, or pipes, and extrapolating this to the leakage that is estimated to be the total contribution by a given company. These methods usually underestimate methane emission rates, regardless of the scale of the inventory. [19]

Addressing issues stemming from fugitive gas emissions

There are some solutions for addressing these issues. Most of them require policy implementation or changes at the company, regulator, or government levels (or all three). Policies can include emission caps, feed-in-tariff programs, and market-based solutions such as taxes or tradeable permits. [28]

Canada has enacted policies which include plans to reduce emissions from the oil and gas sector by 40 to 45% below 2012 levels by 2025. [13] The Alberta government also has plans to reduce methane emissions from oil and gas operations by 45% by 2025. [12]

Reducing fugitive gas emissions could help slow climate change, since methane has a radiative force 25 times that of carbon dioxide when considering a 100 year time frame. [9] [16] Once emitted, methane is also oxidized by water vapour and increases carbon dioxide concentration, leading to further climate effects. [17]

Costs of reducing fugitive gas emissions

Costs related to implementation of policies designed to reduce fugitive gas emissions vary greatly depending on the geography, geology, and hydrology of the production and distribution areas. [14] Often, the cost of reducing fugitive gas emissions falls to individual companies in the form of technology upgrades. This means that there is often a discrepancy between companies of different sizes as to how drastically they can financially afford to reduce their methane emissions.

Addressing and remediating fugitive gas emissions

The process of intervention in the case of leaky wells affected by surface casing vent flows and gas migrations can involve perforating the intervention area, pumping fresh water and then slurry into the well, and remedial cementing of the intervention interval using methods such as bradenhead squeeze, cement squeeze, or circulation squeeze. [25]

See also

Related Research Articles

<span class="mw-page-title-main">Global warming potential</span> Potential heat absorbed by a greenhouse gas

Global warming potential (GWP) is an index to measure how much infrared thermal radiation a greenhouse gas would absorb over a given time frame after it has been added to the atmosphere. The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing radiative forcing". It is expressed as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide, which is taken as a reference gas. Therefore, the GWP has a value of 1 for CO2. For other gases it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered.

<span class="mw-page-title-main">Natural gas</span> Gaseous fossil fuel

Natural gas is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane (95%) in addition to various smaller amounts of other higher alkanes. Traces of carbon dioxide, nitrogen, hydrogen sulfide, and helium are also usually present. Methane is colorless and odorless, and the second largest greenhouse gas contributor to global climate change after carbon dioxide. Because natural gas is odorless, odorizers such as mercaptan are commonly added to it for safety so that leaks can be readily detected.

<span class="mw-page-title-main">Coalbed methane</span> Form of natural gas extracted from coal beds

Coalbed methane, coalbed gas, or coal seam gas (CSG) is a form of natural gas extracted from coal beds. In recent decades it has become an important source of energy in United States, Canada, Australia, and other countries.

A gas leak refers to a leak of natural gas or another gaseous product from a pipeline or other containment into any area where the gas should not be present. Gas leaks can be hazardous to health as well as the environment. Even a small leak into a building or other confined space may gradually build up an explosive or lethal concentration of gas. Natural gas leaks and the escape of refrigerant gas into the atmosphere are especially harmful, because of their global warming potential and ozone depletion potential.

<span class="mw-page-title-main">Carbon capture and storage</span> Collecting carbon dioxide from industrial emissions

Carbon capture and storage (CCS) is a process in which a relatively pure stream of carbon dioxide (CO2) from industrial sources is separated, treated and transported to a long-term storage location. In CCS, the CO2 is captured from a large point source, such as a chemical plant, coal power plant, cement kiln, or bioenergy plant, and typically is stored in a deep geological formation.

<span class="mw-page-title-main">Greenhouse gas emissions</span> Greenhouse gases emitted from human activities

Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide, from burning fossil fuels such as coal, oil, and natural gas, is one of the most important factors in causing climate change. The largest emitters are China followed by the United States. The United States has higher emissions per capita. The main producers fueling the emissions globally are large oil and gas companies. Emissions from human activities have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but have been consistent among all greenhouse gases. Emissions in the 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2022 were 703 GtC, of which 484±20 GtC from fossil fuels and industry, and 219±60 GtC from land use change. Land-use change, such as deforestation, caused about 31% of cumulative emissions over 1870–2022, coal 32%, oil 24%, and gas 10%.

Carbon monitoring as part of greenhouse gas monitoring refers to tracking how much carbon dioxide or methane is produced by a particular activity at a particular time. For example, it may refer to tracking methane emissions from agriculture, or carbon dioxide emissions from land use changes, such as deforestation, or from burning fossil fuels, whether in a power plant, automobile, or other device. Because carbon dioxide is the greenhouse gas emitted in the largest quantities, and methane is an even more potent greenhouse gas, monitoring carbon emissions is widely seen as crucial to any effort to reduce emissions and thereby slow climate change.

<span class="mw-page-title-main">Methane</span> Hydrocarbon compound (CH₄) in natural gas

Methane is a chemical compound with the chemical formula CH4. It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it is difficult because it is a gas at standard temperature and pressure.

Fugitive emissions are leaks and other irregular releases of gases or vapors from a pressurized containment – such as appliances, storage tanks, pipelines, wells, or other pieces of equipment – mostly from industrial activities. In addition to the economic cost of lost commodities, fugitive emissions contribute to local air pollution and may cause further environmental harm. Common industrial gases include refrigerants and natural gas, while less common examples are perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride.

<span class="mw-page-title-main">Greenhouse gas</span> Gas in an atmosphere with certain absorption characteristics

Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. What distinguishes them from other gases is that they absorb the wavelengths of radiation that a planet emits, resulting in the greenhouse effect. The Earth is warmed by sunlight, causing its surface to radiate heat, which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F).

<span class="mw-page-title-main">Atmospheric methane</span> Methane in Earths atmosphere

Atmospheric methane is the methane present in Earth's atmosphere. The concentration of atmospheric methane is increasing due to methane emissions, and is causing climate change. Methane is one of the most potent greenhouse gases. Methane's radiative forcing (RF) of climate is direct, and it is the second largest contributor to human-caused climate forcing in the historical period. Methane is a major source of water vapour in the stratosphere through oxidation; and water vapour adds about 15% to methane's radiative forcing effect. The global warming potential (GWP) for methane is about 84 in terms of its impact over a 20-year timeframe, and 28 in terms of its impact over a 100-year timeframe.

<span class="mw-page-title-main">Greenhouse gas monitoring</span> Measurement of greenhouse gas emissions and levels

Greenhouse gas monitoring is the direct measurement of greenhouse gas emissions and levels. There are several different methods of measuring carbon dioxide concentrations in the atmosphere, including infrared analyzing and manometry. Methane and nitrous oxide are measured by other instruments. Greenhouse gases are measured from space such as by the Orbiting Carbon Observatory and networks of ground stations such as the Integrated Carbon Observation System.

Shale gas in the United Kingdom has attracted increasing attention since 2007, when unconventional onshore shale gas production was proposed. The first shale gas well in England was drilled in 1875. As of 2013 a number of wells had been drilled, and favourable tax treatment had been offered to shale gas producers.

<span class="mw-page-title-main">Aliso Canyon gas leak</span> Massive natural gas leak in southern California

The Aliso Canyon gas leak was a massive methane leak in the Santa Susana Mountains near the neighborhood of Porter Ranch in the city of Los Angeles, California. Discovered on October 23, 2015, gas was escaping from a well within the Aliso Canyon underground storage facility. This second-largest gas storage facility of its kind in the United States belongs to the Southern California Gas Company, a subsidiary of Sempra Energy. On January 6, 2016, Governor Jerry Brown issued a state of emergency. On February 11, the gas company reported that it had the leak under control. On February 18, state officials announced that the leak was permanently plugged.

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% of methane released globally was from human activities, while natural sources contributed about 40%. Reducing methane emissions by capturing and utilizing the gas can produce simultaneous environmental and economic benefits.

<span class="mw-page-title-main">Gas venting</span> Disposal of unwanted methane gas from fossil fuels

Gas venting, more specifically known as natural-gas venting or methane venting, is the intentional and controlled release of gases containing alkane hydrocarbons - predominately methane - into Earth's atmosphere. It is a widely used method for disposal of unwanted gases which are produced during the extraction of coal and crude oil. 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, and distribution.

<span class="mw-page-title-main">Orphan wells in Alberta, Canada</span> Inactive oil or gas sites in Alberta with no solvent owner

Orphan wells in Alberta, Canada are inactive oil or gas well sites that have no solvent owner that can be held legally or financially accountable for the decommissioning and reclamation obligations to ensure public safety and to address environmental liabilities.

<span class="mw-page-title-main">Routine flaring</span> Disposal of unwanted gas during extraction

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 downstream of the wellhead, then released into a flare stack and combusted into Earth's atmosphere. Where performed, the unwanted gas has been deemed unprofitable, and may be referred to as stranded gas, flare gas, or simply as "waste gas". Routine flaring is not to be confused with safety flaring, maintenance flaring, or other flaring practices characterized by shorter durations or smaller volumes of gas disposal.

<span class="mw-page-title-main">Orphan wells</span> Disused oil or gas 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 because had become uneconomic, failure to transfer ownerships, or neglect, and thus no longer have legal owners responsible for their care. Decommissioning wells effectively can be expensive, costing several thousands of dollars for a shallow land well to millions of dollars for an offshore one. Thus the burden may fall on government agencies or surface landowners when a business entity can no longer be held responsible.

<span class="mw-page-title-main">Methane leak</span>

A methane leak comes from an industrial facility or pipeline and means a significant natural gas leak: the term is used for a class of methane emissions. Satellite data enables the identification of super-emitter events that produce methane plumes. Over 1,000 methane leaks of this type were found worldwide in 2022. As with other gas leaks, a leak of methane is a safety hazard: coalbed methane in the form of fugitive gas emission has always been a danger to miners. Methane leaks also have a serious environmental impact. Natural gas can contain some ethane and other gases, but from both the safety and environmental point of view the methane content is the major factor.

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Works cited

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