What does science tell us about fugitive methane emissions from unconventional gas?

This factsheet sets out what the science tells us about methane emission sources from coal seam gas (CSG) wells, pipelines, compressors and other infrastructure associated with CSG production; and their importance in contributing to warming of the earth's climate.


What is methane and where does it come from?

Methane, a colourless, odourless, non-toxic gas, originates from two sources:

Globally, it is estimated that more than 300 million tonnes (Mt) of methane is emitted each year from natural sources such as wetlands, soils, biomass burning and geological sources and another 330 million tonnes (Mt) of methane is produced by human activities such as agriculture; mainly rice and beef production (Kirschke et al., 2013). However, large uncertainties remain in these estimates (Schaefer et al., 2016). Of the natural sources, about 16% is seeping naturally from sedimentary basins such as from coal seams and shale basins, rising from geological structures beneath the earth’s surface. About 29% of human sources of methane emitted to the atmosphere arise from fossil fuel combustion (Kirschke et al., 2013). However, these estimates are still subject to significant uncertainty. The Commonwealth Government estimates that fugitive emissions from natural gas production are about 2.5% (Commonwealth Government, 2014).

How much does methane warm the atmosphere?

Like all greenhouse gases, methane absorbs infra-red radiation from the earth and then radiates this heat back into the surrounding atmosphere, warming it. However, methane is a more potent greenhouse gas than carbon dioxide. About 20% of the total warming of the atmosphere since 1750 is due to methane emissions from human activities, which has increased global average temperatures by about 1 degree Celsius (Kirschke et al., 2013).

The relative capacity of different gases to warm the atmosphere, taking into account their ‘lifetimes’, is called the global warming potential. Methane remains in the atmosphere on average for between eight and twelve years (Lassey et al., 2007), whereas 50% of carbon dioxide emitted to the atmosphere is lost in about 30 years (Inman 2008). The global warming potential of methane, when compared to carbon dioxide over a 100-year lifetime, is about 25 times greater (Saunois et al., 2016; Commonwealth Government 2017).

How much methane is coming from gas production?

Global atmospheric methane concentrations have risen from about 0.7 parts per million (ppm) in 1750 to about 1.8 ppm today. To accurately measure fugitive emissions, natural background biological and geological sources must be separated from human sources.

It is estimated that between between 69 and 88 Mt of methane is emitted by the global oil and gas industry annually. In comparison, emissions from agricultural production of beef and rice are about 135 Mt/yr (Saunois et al., 2016).

Over the past three decades, the rate of global oil and gas methane emissions from gas production have declined from 8% to 2%, as shown by the isotopic composition of methane in the atmosphere (Schwietzke et al., 2016).

How are fugitive methane emissions from the gas industry measured?

CSIRO research underway in Queensland, NSW and WA uses a range of methods to build a comprehensive picture of natural background and fugitive gas industry emissions in Australia.

To understand methane emissions from the CSG industry, multiple approaches are needed, including:

  1. A ‘bottom-up’ approach which directly measures methane fluxes from individual wells, compressors, pipelines, and other infrastructure. The rate of flow, or ‘flux’, of methane from wells and other infrastructure is estimated using a range of measurement techniques. One CSIRO approach is to measure methane concentrations downwind of a well or other source and calculate the emission flux based on knowledge of plume dispersion and local wind speeds.
    A second method uses a tracer gas that is released at a known rate at the methane source. The relationship between known flux and measured concentration of the tracer allows us to infer the flux of methane from co-measured concentrations. These flux measurements are used by the Commonwealth Government to generate Australia-specific emissions factors which are then used to estimate total fugitive emissions from gas production. Fugitive emission estimates for the industry are reported in the Commonwealth Government’s National Greenhouse Gas Accounts to the United Nations Framework Convention on Climate Change.
    CSIRO’s ‘bottom-up’ research (Day et al., 2012; Day et al., 2013; Day et al., 2014; Day et al., 2015; Day et al., 2016; Day et al., 2017) consists of sensitive methane measurements adjacent to gas infrastructure, combined with meteorological measurements of wind speed and direction. Researchers use a Picarro spectrometer, sensitive to concentrations of parts per billion, mounted in a vehicle to undertake measurements along access roads. These gas concentration measurements are combined in a physical model of gas plume dispersion to provide methane fluxes estimates.
    In another approach, researchers use three-metre high towers equipped with methane sensors and meteorological equipment to provide concentration measurements, meteorological observations and estimates of methane fluxes over a wider area of the size of a farmer’s field.
  2. ‘Top-down’ methods calculate emissions rates by measuring atmospheric concentrations of methane at different times and using meteorological information on wind speed and direction. Typically, ‘top-down’ methods are applied at a much larger scale than ‘bottom-up’ measurements up to the size of an entire gas producing region.
    CSIRO’s ‘top-down’ projects (Etheridge et al., 2016) use 10-metre towers situated upwind and downwind of the gas production fields in the Surat Basin, Queensland. These two towers measure changes in methane concentrations as air passes across the gas production field and, when combined with a physical model of atmospheric transport, can tell us about methane fluxes coming from areas of a few square kilometres. Repeated measurements combined with meteorological observations and a physical model of atmospheric transport are used to determine fluxes over many tens of square kilometres.
  3. A ‘lifecycle analysis’ which follows gas industry processes from production at the gas well through the Liquefied Natural Gas (LNG) compression plant, transport, and offloading, decompression and combustion of the gas for electricity generation. A lifecycle analysis allows comparisons of greenhouse emissions with other forms of electricity generation such as coal and renewables and is dependent on obtaining accurate information on these processes.

What is CSIRO research showing?

Here is a snapshot of CSIRO research on methane emissions in gas development regions:

* A ‘standard cow’ is based on beef cattle producing 0.17 kg of methane daily per animal.

What is research in the United States showing?

Gas production in the US has many differences compared to Australia due to history of gas development, size of the industry, dominance by shale gas over CSG production, differences in environmental regulatory controls and laws governing land owner rights over resources.

US research on fugitive emissions from the petroleum sector has focussed on reconciling different estimates from both national inventories (Environmental Protection Agency data and the Emissions Database for Global Atmospheric Research) and from regional measurement and modelling studies focussed on individual production fields. Despite regional ‘hotspots’ of methane emissions in some oil and gas regions, overall US inventory estimates of fugitive emissions are lower than simple extrapolation of these regional studies would suggest (Miller et al., 2013) because these regional discrepancies are not representative of nationwide natural gas leakage rates (Allen et al., 2013). Also, part of the discrepancy may be due to the regional studies not adequately separating background emissions, such as natural seeps of methane, from fugitive emissions (Brandt et al., 2014).

Abandoned wells may also be a source of methane in the US, where 130 years of oil and gas production has led to significant legacy issues from old wells in regions such as the Marcellus Shales in Pennsylvania, which was constructed under less strict environmental regulatory controls than in place in Australia today. Based on measurements of 19 abandoned shale gas wells (Kang et al., 2014), a median methane emissions rate of 0.0013 kg/day was observed (mean =  0.27 kg/day), well below a single cow’s daily methane emissions.

This fact sheet will be updated as more CSIRO research is completed to give the most accurate estimates possible of fugitive emissions from the unconventional gas industry in Australia.


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Brandt, AR, Heath, GA, Kort, EA, O’Sullivan, F, Pétron, G, et al., (2014) Methane Leaks from North American Natural Gas Systems. Science 343, 733–735.

Commonwealth Government (2017) Australian Government Department of Environment and Energy National Inventory Report 2015 (revised) Vol 1.

Day, S, Connell, L, Etheridge, D, Norgate, T, Sherwood, N, (2012) Fugitive Greenhouse Gas Emissions from Coal Seam Gas Production in Australia. CSIRO, Australia. 33 p.

Day, S, Dell ‘Amico, M, Etheridge, DM, Ong, C, Rodger, A, et al., (2013) Characterisation of Regional Fluxes of Methane in the Surat Basin, Queensland. Phase 1: A review and analysis of literature on methane detection and flux determination. 55 p.

Day, S., Dell’Amico, M, Fry, R., Javanmard Tousi, H., (2014) Field Measurements of Fugitive Emissions from Equipment and Well Casings in Australian Coal Seam Gas Production Facilities. CSIRO, Australia. 47 p.

Day, S, Ong, C, Rodger, A, Etheridge, DM, Hibberd, M, et al., (2015) Characterisation of Regional Fluxes of Methane in the Surat Basin, Queensland. Phase 2: Pilot study to detect and quantify methane sources. Report for the Gas Industry Social and Environmental Research Alliance (GISERA), Project No, GAS1315. 74 p.

Day, S, Marvig, P, White, S, Halliburton, B, (2017). Methane emissions from CSG well completion activities. CSIRO, Australia. 31 p.

Day, S, Tibbett, A, Sestak, S, Knight, C, Marvig, P, McGarry, S, Weir, S, White, S, Armand, S, van Holst, J, Fry, R, Dell’Amico, M, Halliburton, B, Azzi, M, (2016). Methane and Volatile Organic Compound Emissions in New South Wales. CSIRO, Australia. 312 p.

Etheridge, DM, Day, S, Hibberd, MF, Luhar, A, Spencer, DA, et al., (2016) Characterisation of Regional Fluxes of Methane in the Surat Basin, Queensland. The continuous monitoring results – installation, commissioning and operation of two field stations and preliminary data Milestone 3.1 GISERA Greenhouse Gas Research – Phase 3. 19 p. https://gisera.org.au/wp-content/uploads/2013/08/GISERA-Methane-Seepage-Fluxes-project_Phase-3.1-Interim-Report_final.pdf

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Kang, M, Kannoa, CM, Reida, MC, Zhang, X, Mauzeralla, DL, et al., (2014) Direct measurements of methane emissions from abandoned oil and gas wells in Pennsylvania. 111, 18173–18177.

Kirschke, S, Bousquet, P, Ciais, P, Saunois, M, Canadell, JG, et al., (2013) Three decades of global methane sources and sinks. Nature Geoscience. 6, 813–823.

Lassey, KR, Etheridge, DM, Lowe, DC, Smith, AM, Ferretti, DF, (2007) Centennial evolution of the atmospheric methane budget: what do the carbon isotopes tell us? Atmospheric Chemistry and Physics. 7, 2119–2139.

Miller, SM, Wofsy, SC, Michalak, AM, Kort, EA, Andrews, AE, et al., (2013) Anthropogenic emissions of methane in the United States. Proceedings of the National Academy of Sciences.

Queensland Government (2013) Code of practice for constructing and abandoning coal seam gas wells and associated bores in Queensland. Department of Natural Resources and Mines, Queensland Government.

O’Sullivan, F, and Paltsev, S, (2012) Shale gas production: potential versus actual greenhouse gas emissions. Environmental Research Letters. doi:10.1088/1748-9326/7/4/044030.

Saunois, M, Bousquet, P, Poulter, B, Peregon, A, Ciais, P, et al., (2016) The global methane budget 2000–2012 Earth System Science Data, 8, 1–55.

Schaefer, H, Mikaloff Fletcher, SE, Veidt, C, Lassey, KR, Brailsford,GW et al., (2016) A 21st-century shift from fossil-fuel to biogenic methane emissions indicated by 13CH4. Science 352, 80–84.

Schwietzke, S, Sherwood, OA, Bruhwiler, LMP, Miller, JB, Etiope, G, et al., (2016) Nature, 538, 88–91.


For further information

CSIRO Energy
Damian Barrett
t +61 2 6246 5856
e damian.barrett@csiro.au
w www.csiro.au/Research/EF/Areas/Oil-gas-and-fuels/Onshore-gas/Environmental-impacts