Coalbed methane

Short description: Form of natural gas extracted from coal beds

A German methane detector used for coal mining in the 1960s.

Coalbed methane (CBM or coal-bed methane),[1] coalbed gas, or coal seam gas (CSG)[1] is a form of natural gas extracted from coal beds.[2] In recent decades it has become an important source of energy in United States, Canada, Australia, and other countries.

Unlike much natural gas from conventional reservoirs, coalbed methane contains very little heavier hydrocarbons such as propane or butane, and no natural-gas condensate. It often contains up to a few percent carbon dioxide. Coalbed methane is generally formed due to thermal maturation of kerogen and organic matter, in contrast to coal seams with regular groundwater recharge where methane is typically generated by microbial communities living in situ.[3][4]

## Contents

* 1 History
* 2 Reservoir properties
* 2.1 Porosity
* 2.2 Adsorption capacity
* 2.3 Fracture permeability
* 2.4 Thickness of formation and initial reservoir pressure
* 2.5 Other properties
* 3 Extraction
* 4 Environmental impacts
* 4.1 Methane
* 4.2 Infrastructure
* 4.3 Produced water
* 4.3.1 Pilliga Scrub
* 4.3.2 Powder River Basin
* 4.4 Groundwater
* 4.5 Power generation
* 5 Coalbed methane producing areas
* 5.1 Australia
* 5.2 Canada
* 5.3 United Kingdom
* 5.4 United States
* 5.5 Kazakhstan
* 5.6 India
* 6 See also
* 7 References
* 8 External links

## History

Coalbed methane grew out of venting methane from coal seams. Some coal beds have long been known to be "gassy" so, as a safety measure, boreholes were drilled into the seams from the surface, and the methane allowed to vent before mining.

Coalbed methane as a natural-gas resource received a major push from the US federal government in the late 1970s. Federal price controls were discouraging natural gas drilling by keeping natural gas prices below market levels; at the same time, the government wanted to encourage more gas production. The US Department of Energy funded research into a number of unconventional gas sources, including coalbed methane. Coalbed methane was exempted from federal price controls, and was also given a federal tax credit.

In Australia, commercial extraction of coal seam gas began in 1996 in the Bowen Basin of Queensland.[5]

## Reservoir properties

Gas contained in coal bed methane is mainly methane and trace quantities of ethane, nitrogen, carbon dioxide, and few other gases. Intrinsic properties of coal as found in nature determine the amount of gas that can be recovered.

### Porosity

Coalbed methane reservoirs are considered as a dual-porosity reservoirs. Dual porosity reservoirs are reservoirs in which porosity related to cleats (natural fractures) are responsible for flow behavior and reservoir porosity of the matrix is responsible for the storage of gas. The porosity of a coalbed methane reservoir can vary from 10%-20%; However, the cleat porosity of the reservoir is estimated to be in the range of 0.1%-1%[6]

### Adsorption capacity

Adsorption capacity of coal is defined as the volume of gas adsorbed per unit mass of coal usually expressed in SCF (standard cubic feet, the volume at standard pressure and temperature conditions) gas/ton of coal. The capacity to adsorb depends on the rank and quality of coal. The range is usually between 100 and 800 SCF/ton for most coal seams found in the US. Most of the gas in coal beds is in the adsorbed form. When the reservoir is put into production, water in the fracture spaces is pumped off on first. This leads to a reduction of pressure enhancing desorption of gas from the matrix.[7]

### Fracture permeability

Fracture permeability acts as the major channel for the gas to flow. The higher the permeability, the higher the gas production. For most coal seams found in the US, the permeability lies in the range of 0.1–50 milliDarcys. The permeability of fractured reservoirs changes with the stress applied to them. Coal displays a stress-sensitive permeability and this process plays an important role during stimulation and production operations[8] .[9] Fracture permeability in Coalbed methane reservoir tends to increase with depletion of gas; in contrast to conventional reservoirs. This unique behavior is because of shrinking of coal, when methane is released from its matrix, which results in opening up of fractures and increased permeability.[10] It is also believed that due to shrinkage of coal matrix at lower reservoir pressures, there is a loss of horizontal stress in the reservoir which induces in-situ failure of coal. Such a failure has been attributed to sudden decrease in the fracture permeability of the reservoir[11][9]

### Thickness of formation and initial reservoir pressure

For example, it has been observed in the Cherokee Basin in Southeast Kansas that a well with a single zone of 1 to 2 feet (0.3 to 0.6 m) of pay can produce excellent gas rates, whereas an alternative formation with twice the thickness can produce next to nothing. Some coal (and shale) formations may have high gas concentrations regardless of the formation's thickness, probably due to other factors of the area's geology.

### Other properties

## Extraction

Diagram of a coalbed methane well (US DOE) Typical production profile of a coalbed methane well (USGS)

Main article: Chemistry:Coalbed methane extraction

To extract the gas, a steel-encased hole is drilled into the coal seam 100 to 1,500 metres (330 to 4,920 ft) below ground. As the pressure within the coal seam declines due to natural production or the pumping of water from the coalbed, both gas and produced water come to the surface through tubing. Then the gas is sent to a compressor station and into natural gas pipelines. The produced water is either reinjected into isolated formations, released into streams, used for irrigation, or sent to evaporation ponds. The water typically contains dissolved solids such as sodium bicarbonate and chloride but varies depending on the formation geology.[12]

Coalbed methane wells often produce at lower gas rates than conventional reservoirs, typically peaking at near 300,000 cubic feet (8,500 m3) per day (about 0.100 m³/s), and can have large initial costs. The production profiles of CBM wells are typically characterized by a "negative decline" in which the gas production rate initially increases as the water is pumped off and gas begins to desorb and flow. A dry CBM well is similar to a standard gas well.

"Beyond conventional methods, research institutions like The Energy and Resources Institute (TERI) in India are investigating microbial techniques to enhance methane recovery from coal beds, with reported successful field trials."[13]

## Environmental impacts

### Methane

As with all carbon-based fossil fuels, burning coalbed methane releases carbon dioxide (CO2) into the atmosphere. Its effect as greenhouse gas was first analyzed by chemist and physicist Svante Arrhenius. CBM production also entails leaks of fugitive methane into the atmosphere. Methane is rated as having 72 times the effect on global warming per unit of mass than CO2. over 20 years, reducing to 25 times over 100 years and 7.5 times over 500 years.[14] Analysis of life-cycle greenhouse gas emissions of energy sources indicates that generating electricity from CBM, as with conventional natural gas, has less than half the greenhouse gas effect of coal.[15]

Globally, coal mining is also a significant source of methane emissions.[16] To identify the volumes, the industry, governments, and NGOs rely on a combination of emissions monitoring and reporting, estimates, and satellite observations. The current methods for estimating emissions at the coal mine level rely on activity data from the operation and the methane gas content of the coal seams. The emissions methodologies for several academic studies, and NGOs like Global Energy Monitor and Climate Trace, are publicly available.[17]

Multiple Australian studies have indicated the long term negative environmental effects of coal seam gas extraction, both locally and globally.[18][19][20][21][22]

In the United States, methane escaping from coal during mining amounts to seven percent of total methane emissions.[23] Recovery of coal mine methane in advance of mining is seen as a major opportunity to reduce methane emissions. Companies like CNX Resources have methane abatement programs to reduce greenhouse gas emissions from active and closed mines.[24]

### Infrastructure

CBM wells are connected by a network of roads, pipelines, and compressor stations. Over time, wells may be spaced more closely in order to extract the remaining methane.

### Produced water

The produced water brought to the surface as a byproduct of gas extraction varies greatly in quality from area to area, but may contain undesirable concentrations of dissolved substances such as salts, naturally present chemicals, heavy metals, and radionuclides.[25] In many producing regions the water is treated, such as through a reverse osmosis plant and used beneficially for irrigation, water for livestock, urban and industrial uses, or dust suppression.

#### Pilliga Scrub

In 2012 Eastern Star Gas was fined for "discharging polluting water containing high levels of salt into Bohena Creek" in the Pilliga Scrub.[26] There were "16 spills or leaks of contaminated water" including "serious spills of saline water into woodland and a creek."[27] In 2012, a NSW Legislative Council[28] inquiry criticised the use of open holding ponds, recommending that "the NSW Government ban the open storage of produced water."[28][29]

#### Powder River Basin

Not all coalbed methane produced water is saline or otherwise undesirable. Water from coalbed methane wells in the Powder River Basin of Wyoming, US, commonly meets federal drinking water standards, and is widely used in the area to water livestock.[30] Its use for irrigation is limited by its relatively high sodium adsorption ratio.

### Groundwater

Depending on aquifer connectivity, water withdrawal may depress aquifers over a large area and affect groundwater flows.[31] In Australia, the CBM industry estimates extraction of 126,000 million litres (3.3×1010 US gallons) to 280,000 million litres (7.4×1010 US gallons) of groundwater per year; while the National Water Commission estimates extraction above 300,000 million litres (7.9×1010 US gallons) a year.[25]

### Power generation

In 2012, the Aspen Skiing Company built a 3-megawatt methane-to-electricity plant in Somerset, Colorado at Oxbow Carbon's Elk Creek Mine.[32]

## Coalbed methane producing areas

### Australia

Coal seam gas resources are in the major coal basins in Queensland and New South Wales, with further potential resources in South Australia. Commercial recovery of coal seam gas (CSG) began in Australia in 1996. As of 2014, coal seam gas, from Queensland and New South Wales, made up about ten percent of Australia's gas production. Demonstrated reserves were estimated to be 33 trillion cubic feet (35 905 petajoules) as of January 2014.[33]

* Bowen Basin
* Surat Basin
* Sydney Basin

### Canada

In Canada, British Columbia is estimated to have approximately 90 trillion cubic feet (2.5 trillion cubic metres) of coalbed gas. Alberta, in 2013, was the only province with commercial coalbed methane wells and is estimated to have approximately 170 trillion cubic feet (4.8 trillion cubic metres) of economically recoverable coalbed methane, with overall reserves totaling up to 500 trillion cubic feet (14 trillion cubic metres).[34][35]

Coalbed methane is considered a non-renewable resource, although the Alberta Research Council, Alberta Geological Survey and others have argued coalbed methane is a renewable resource because the bacterial action that formed the methane is ongoing. This is subject to debate since it has also been shown that the dewatering that accompanies CBM production destroys the conditions needed for the bacteria to produce methane[36] and the rate of formation of additional methane is undetermined. This debate is currently causing a right of ownership issue in the Canadian province of Alberta, as only non-renewable resources can legally be owned by the province.[37]

### United Kingdom

Although gas in place in Britain's coal fields has been estimated to be 2,900 billion cubic meters, it may be that as little as one percent might be economically recoverable. Britain's CBM potential is largely untested. Some methane is extracted by coal mine venting operations, and burned to generate electricity. Assessment by private industry of coalbed methane wells independent of mining began in 2008, when 55 onshore exploration licences were issued, covering 7,000 square kilometers of potential coalbed methane areas. IGas Energy became the first in the UK to commercially extract coalbed methane separate from mine venting; as of 2012, the Igas coalbed methane wells at Doe Green, extracting gas for electrical generation, were the only commercial CBM wells in the UK.[38] The use of CBM (in GWh) for electricity generation, coal extraction, and other industries in the UK is as shown.

### United States

United States coalbed methane production in 2017 was 1.76 trillion cubic feet (TCF), 3.6 percent of all US dry gas production that year. The 2017 production was down from the peak of 1.97 TCF in 2008.[39] Most CBM production came from the Rocky Mountain states of Colorado, Wyoming, and New Mexico.

### Kazakhstan

Kazakhstan could witness the development of a large coalbed methane (CBM) sector over the coming decades, according to industry professionals.[40] Preliminary research suggests there may be as much as 900 billion m3 of gas in Kazakhstan's main coalfields – 85% of all reserves in Kazakhstan.

### India

Great Eastern Energy (GEECL) was the first company with a field development plan approved. With the completion of the drilling of 23 vertical production wells by GEECL, coalbed methane became commercially available in India on 14 July 2007 with CNG priced at ₹30 per kg. Initially 90% of the CBM would be distributed as CNG gas to fuel vehicles.

GEECL is responsible for Southeast Asia's first CBM station and is also locating one in the West Bengal city of Asansol.

Prashant Modi, President and Chief Operating Officer of GEECL, said, "With the nation requiring higher energy sources to sustain its development pace, we are confident that CBM will play an important role as one of the prime energy sources for the future generations."[41]

Essar Group's Essar Oil and Gas Exploration and Production Ltd.'s CBM portfolio includes 5 blocks. Currently, only one of them, Raniganj East, is currently operational. The others include Rajmahal in Jharkhand, Talcher and Ib Valley in Odisha, and Sohagpur in Madhya Pradesh. The 5 blocks possess an estimated 10 trillion cubic feet (CBF) of CBM reserves.

## See also

* Firedamp
* Underground coal gasification
* Western Canada Sedimentary Basin

## References

1. ↑ 1.0 1.1 "Jargon Buster". BG Group. http://www.bg-group.com/Careers/graduates/howtoapply/Pages/JargonBuster.aspx.
2. ↑ Coal Gas, clarke-energy.com, retrieved 25.11.2011
3. ↑ Laubach, S. E; Marrett, R. A; Olson, J. E; Scott, A. R (1998-02-01). "Characteristics and origins of coal cleat: A review" (in en). International Journal of Coal Geology 35 (1): 175–207. doi:10.1016/S0166-5162(97)00012-8. ISSN 0166-5162. Bibcode: 1998IJCG...35..175L. http://www.sciencedirect.com/science/article/pii/S0166516297000128.
4. ↑ Saurabh, Suman; Harpalani, Satya (2018-03-15). "Modeling of microbial methane generation from coal and assessment of its impact on flow behavior" (in en). Fuel 216: 274–283. doi:10.1016/j.fuel.2017.12.015. ISSN 0016-2361. Bibcode: 2018Fuel..216..274S. http://www.sciencedirect.com/science/article/pii/S001623611731582X.
5. ↑ Geoscience Australia, Coal seam gas , accessed 10 October 2013.
6. ↑ C.R. Clarkson, Production data analysis of unconventional gas wells: Review of theory and best practices, International Journal of Coal Geology, Volume 109, 2013, Pages 101-146, ISSN 0166-5162, https://dx.doi.org/10.1016/j.coal.2013.01.002
7. ↑ Moore, Tim A. (2012-11-01). "Coalbed methane: A review" (in en). International Journal of Coal Geology 101: 36–81. doi:10.1016/j.coal.2012.05.011. ISSN 0166-5162. Bibcode: 2012IJCG..101...36M. http://www.sciencedirect.com/science/article/pii/S0166516212001760.
8. ↑ McKee, C. R., Bumb, A. C., & Koenig, R. A. (1 March 1988). Stress-Dependent Permeability and Porosity of Coal and Other Geologic Formations. Society of Petroleum Engineers. doi:10.2118/12858-PA
9. ↑ 9.0 9.1 S. Saurabh, S. Harpalani, V.K. Singh, Implications of stress re-distribution and rock failure with continued gas depletion in coalbed methane reservoirs, International Journal of Coal Geology, Volume 162, 2016, Pages 183-192, ISSN 0166-5162, https://dx.doi.org/10.1016/j.coal.2016.06.006.
10. ↑ Sevket Durucan, Mustafa Ahsanb, Ji-Quan Shia, Matrix shrinkage and swelling characteristics of European coals, Energy Procedia, Volume 1, Issue 1, 2009, Pages 3055-3062, ISSN 1876-6102, https://dx.doi.org/10.1016/j.egypro.2009.02.084.
11. ↑ Okotie, V. U., & Moore, R. L. (1 May 2011). Well-Production Challenges and Solutions in a Mature, Very-Low-Pressure Coalbed-Methane Reservoir. Society of Petroleum Engineers. doi:10.2118/137317-PA
12. ↑ "Coalbed Methane Extraction: Detailed Study Report". EPA: pp. 63–70. December 2010. https://nepis.epa.gov/Exe/ZyPDF.cgi/P100MQJE.PDF?Dockey=P100MQJE.PDF.
13. ↑ "Microbial Innovation for Coalbed Methane: TERI's Role in Advancing CBM Technology" (in en). https://teriin.org/article/microbial-innovation-coalbed-methane-teris-role-advancing-cbm-technology.
14. ↑ IPCC Fourth Assessment Report, Table 2.14, Chap. 2, p. 212
15. ↑ Timothy J. Skone, Life-cycle analysis , 12 May 2011.
16. ↑ Ryan Driskell Tate, Bigger Than Oil or Gas? Sixing Up Coal Mine Methane Emissions, March 2022
17. ↑ Christy Lewis, Ryan Driskell Tate, Dorothy Lan Mei, Fossil Fuel Operations Sector-Coal Mining Emissions, 2025
18. ↑ Assan, Sabina; Ember : coal to clean (8 July 2022). "Tackling Australia's coal mine methane problem" (in en). https://www.lockthegate.org.au/ember_report.
19. ↑ "Salt in the wound : An assessment of the scale of the NSW Government's planned expansion of Santos' Narrabri coal seam gas field" (in en). 31 August 2021. https://www.lockthegate.org.au/salt_in_the_wound_report_august_21.
20. ↑ Forcey, Tim (17 May 2017). "Infrared video-recording methane emissions in the Queensland coal seam gas fields, February 2017" (in en). Lock the Gate. https://www.lockthegate.org.au/flir_camera.
21. ↑ Davey, Alistair; Fisher, Roger; Pegasus Economics; Lock the Gate Alliance (1 August 2019). "Report on the Narrabri gas project". Lock the Gate. https://www.lockthegate.org.au/pegasus_economics_report_on_the_narrabri_gas_project.
22. ↑ Lock the Gate Alliance (23 March 2016). "Free-loaders : air and water pollution from NSW coalmines". in Wright, Ian. https://www.lockthegate.org.au/freeloaders.
23. ↑ Krawczyk, Kathryn (2021-04-28). "Methane from abandoned coal mines could fight climate change" (in en-US). http://energynews.us/2021/04/28/methane-from-abandoned-coal-mines-could-be-key-to-fight-climate-change-if-only-it-made-more-money/.
24. ↑ "CNX Looking to Capture Methane from Appalachia Operations for Biodegradable Plastic" (in en-US). 2022-07-15. https://www.naturalgasintel.com/cnx-looking-to-capture-methane-from-appalachia-operations-for-biodegradable-plastic/.
25. ↑ 25.0 25.1 "The coal seam gas rush". Australia: ABC News. April 2012. http://www.abc.net.au/news/specials/coal-seam-gas-by-the-numbers/.
26. ↑ "Eastern Star Gas fined for pollution in the Pilliga". Office of Environment and Heritage website. Office of Environment and Heritage. 6 July 2012. http://www.epa.nsw.gov.au/epamedia/epamedia12070601.htm.
27. ↑ Validakis, Vicky (13 June 2013). "Santos to be prosecuted for Pilliga pollution". Australian Mining. Cirrus Media. http://www.miningaustralia.com.au/news/santos-to-be-prosecuted-for-pilliga-pollution.
28. ↑ 28.0 28.1 "Coal seam gas (Inquiry)". Parliament of New South Wales website. State of New South Wales (NSW Parliament). 2012. http://www.parliament.nsw.gov.au/Prod/parlment/committee.nsf/0/29AE48525CFAEA7CCA2578E3001ABD1C?open&refnavid=CO3_1 Report.
29. ↑ Coutts, Sharona (26 October 2012). "Pillaging The Pilliga". The Global Mail. Digital Global Mail. http://www.theglobalmail.org/feature/pillaging-the-pilliga/447/.
30. ↑ US EPA, [Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs, The Powder River Basin], June 2004, EPA 816-R-04-003 Attachment 5.
31. ↑ Montana State University; Frequently Asked Questions; Coal Bed Methane (CBM)
32. ↑ Ward, Bob (21 November 2014). "How Aspen Skiing Co. became a power company" (in en-US). https://www.aspentimes.com/news/how-aspen-skiing-co-became-a-power-company/.
33. ↑ Geoscience Australia, Australian Energy Resource Assessment, 2014. http://www.ga.gov.au/scientific-topics/energy/resources/australian-energy-resource-assessment
34. ↑ John Squarek and Mike Dawson, Coalbed methane expands in Canada, Oil & Gas Journal, 24 July 2006, p.37-40.
35. ↑ "Government of Alberta". 19 September 2023. http://www.albertacanada.com/business/industries/og-natural-gas-and-coal-bed-methane.aspx.
36. ↑ "Renewable Natural Gas? The Discovery of Active Methane Biogenesis in Coalbeds". Green Car Congress. 16 November 2004. http://www.greencarcongress.com/2004/11/renewable_natur.html.
37. ↑ "TELUS, news, headlines, stories, breaking, canada, canadian, national". Mytelus.com. http://www.mytelus.com/ncp_news/article.en.do?pn=tech&articleID=2970245.
38. ↑ DECC, The Unconventional Hydrocarbon Resources of Britain's Onshore Basins – Coalbed Methane , 2012.
39. ↑ US Energy Information Administration, Coalbed methane production, accessed 9 October 2013.
40. ↑ "Coal bed methane in Kazakhstan". worldcoal.com. 23 July 2014. http://www.worldcoal.com/news/cbm/articles/Developing-the-coalbed-methane-industry-in-Kazakhstan-CBM83.aspx.
41. ↑ "Coal Bed Methane in India". http://www.methanetomarketsindia.com/news/GEECL.pdf.

## External links

* The latest CBM news
* U.S. Geological Survey page on CBM
* U.S. Environmental Protection Agency page on CBM
* British Columbia Ministry of Energy, Mines and Petroleum Resources guide to coalbed gas
* Kansas Geological Survey guide to Coalbed Methane
* Coalbed Methane Gas
* Coal seam gas: by the numbers Australian Broadcasting Corporation

* v
* t
* e

Fuel gas

Types|

| Manufactured fuel gas
(History)|

* Coal gas
* Coal gasification
* Underground coal gasification
* Biogas
* Blast furnace gas
* Blau gas
* Gasification
* Landfill gas
* Mond gas
* Pintsch gas
* Producer gas
* Regasification
* Syngas
* Water gas
* Wood gas

|

Natural gas|

* APG
* CBM
* CNG
* HCNG
* LNG
* NGC
* SNG
* Bio-SNG

LPG|

* Autogas
* Butane
* Propane

Infrastructure|

* Compressor station
* Gas carrier
* Gas holder
* Gas meter
* Gasworks
* Natural-gas processing
* Natural gas storage
* Odorizer
* Pipeline transport

Uses|

* Bunsen burner
* Gas burner
* Gas engine
* Gas heater
* Gas lighting
* Gas mantle
* Gas stove
* Gas turbine
* Pilot light

0.00

(0 votes)

Original source: https://en.wikipedia.org/wiki/Coalbed methane. Read more

|

Retrieved from "https://handwiki.org/wiki/index.php?title=Chemistry:Coalbed_methane&oldid=4179057"
*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template