Coal Bed Methane (CBM), sometimes called Coal Seam Gas (mainly in Australia), is Shale Gas’s less well known but equally destructive sibling in “the family” of extreme energy methods. Where once, if a coal seam was too deep, too thin or too fractured to mine that was the end of it, now with rising energy prices and constrained supplies more extreme methods are contemplated. If the seam is close enough to the surface, this is likely to mean open cast mining. But, for deeper coal seams the worst that can be done at the moment is to try to exploit any gas associated with the seam. I say at the moment because slightly further along the extreme energy road we are heading down is the threat of Underground Coal Gasification (UCG), probably the most dangerous and destructive fossil fuel exploitation method that has so far been considered (with the possible exception of the even more speculative Methane Clathrate Mining). That, however, is a topic for another post. In the mean time CBM is a serious threat that already been widely developed in the United States and Australia and is ready to roll out across the British Isles.
Schematic of the Coal Bed Methane extraction process, including well and produced water pumping system
Despite being less well known than Shale Gas, Coal Bed Methane, is, if anything, somewhat more advanced in the British Isles than Shale Gas and poses as large or larger threat to communities and the environment. There is planning permission for around 60 CBM wells in the British Isles compared to at most a dozen Shale Gas wells. The main reason that Coal Bed Methane has been flying under the radar seems to be that gas extraction from coal seams has been going on for quite some time, abet in a very different form. Sealing up old mines and piping away the gas that builds up in them is pretty much the simplest way to get gas out of coal formations and has been happening on a small scale for a while, particularly in South Yorkshire and the East Midlands. However recently more aggressive methods of methane extraction from coal seams have been imported from the United States. This involves drilling into coal seams using the sort of technology more usually used by the oil and gas industry, and using somewhat similar sorts of methods to Shale Gas. However, there are some significant technical differences between CBM and Shale Gas, though in practice it makes little difference to the overall effects.
A CBM well in the San Juan basin, New Mexico, undergoing process of cavitation to create an underground chamber that expands the contact of the cleat system with the well bore, to increase gas flow
The basic method (as with Shale Gas extraction) is to drill into the gas containing rock formation, though for CBM it is a coal seam rather than a layer of shale. As with Shale Gas, more effort is needed to get the gas out though. Unlike Shale Gas where the basic technique used, hydraulic fracturing, is almost always the same, for Coal Bed Methane a wide variety of techniques are used depending on the nature of the coal seam. If the seam is permeable enough, pumping water out of the seam will be enough to start gas flowing from the well, but if not, some sort of stimulation will be needed. Often this is hydraulic fracturing, like that used for Shale Gas, but an even more extreme technique called cavitation (also known as open-hole cavity completion) can also be used, which involves pumping water and air or foam into the well under very high pressure and then suddenly releasing the pressure (sometimes likened to opening a shaken fizzy drink) causing gas, water, coal and rock fragments to explode out of the well. This can last up to 15 minutes and be repeated dozens of times and results in an enlargement of the initially drilled hole (well bore) by as much as 16 feet in diameter in the coal seam, as well as producing fractures that extend from the well bore. Even if it isn’t necessary initially wells are often cavitated later on to try to slow the inevitable decline in gas production.
However in some respects the technique used is of secondary importance. Unlike Shale Gas, the coal seams that are exploited in this process tend to be relatively close to the surface, usually less than 1000 metres down, whereas the Bowland Shale in Lancashire can be at depths of more that 3000 metres. The closer proximity to the surface combined with the fact that it almost always involves pumping large quantities of water out of the coal seam (water that has been marinading in coal for thousands of years) means that the problems with water pollution and leaking methane tend to occur regardless of whether fracking is performed. Being closer to the surface the chances of methane migrating to surface (with the effects of fracking) are higher and the large amounts of water that need to be pumped out of the coal seam (produced water) and disposed of somehow, means the chances water contamination. The produced water can by up to five times as salty as seawater and contain a wide variety of toxic contaminants. The cost to treat and dispose of the produced water can be a critical factor in the viability of a coal bed methane project (producing a strong economic incentive to cut corners and dump produced water illegally). Also, due to generally being much closer to the surface and the large amounts of water that need to be pumped out of the coal seams, subsidence can also be an issue. The massive pumping of ground water can also negatively affect water tables and aquifer levels.
As with the exploitation of Shale Gas, Coal Bed Methane requires that very large numbers of wells need to be drilled. During the recent boom in Coal Bed Methane in the United States over 5000 CBM wells per year have typically been drilled. However despite these high levels of drilling effort CBM production now appears to have peaked and in most US states with significant CBM production output is declining. The problems associated with Coal Bed Methane in the United States have often been similar to those experienced with Shale Gas. A good example of the impacts of CBM can be found in the San Juan basin of northern New Mexico which ranks second only in CBM gas produced to the Powder River basin of Wyoming. Some 23,000 wells producing wells feed gas through 3,000 compressors stations into a massive pipeline system in the high desert of canyons and mesas. Formerly known for ancient pueblo peoples and more recently Apache, Ute and Navajo reservations and cattle ranching, the landscape has been massively industrialised by CBM. Water contamination, air pollution, increased traffic, accidents, spills etc. came as part of the package. Now the ranchers are struggling because of the numbers of cattle being poisoned by the contaminated water.
Extensive coalbed methane (CBM) infrastructure in the San Juan Basin, New Mexico surrounding places sacred to the Navajo and other native peoples
While Coal Bed Methane extraction has been underway in the United States for a while particularly in Colorado, New Mexico, and Wyoming, Australia has more recently seen a significant amount exploitation of CBM (usually referred to as Coal Seam Gas there). In Queensland alone over 3,000 wells have been drilled with projections of 40,000 to come. As with the US this has resulted in widespread environmental and social issues. Coal Bed Methane extraction is now spreading across the global most often into areas that had or continue to have large amounts of coal mining. While the UK has been extensively mined for coal, with peak production occurring in the 1930s, and mine-able coal is now largely exhausted (though companies like UK Coal are busy eking out the last dregs with horrendous open cast mines), there is still a lot of coal that is too deep or in some other way uneconomic to mine. This would be the target of Coal Methane Methane exploitation. In particular traditional coal mining areas like the North East, the Midlands, South Wales and Scotland are threatened, but other areas that have never seen any significant coal mining may also have deep coal seams that could be exploited.
Unlike Shale Gas where there is a clear leader in the race to exploit it in the form of Cuadrilla Resources, for Coal Bed Methane there are number of different companies that are well advanced in their schemes. These companies include Dart Energy (Scotland), Greenpark Energy (Yorkshire and Scotland) which was recently bought by Dart Energy, IGas Energy (Cheshire) and UK Methane (South Wales). In particular IGas Energy and Dart Energy (who bought out the the previous company Composite Energy) are already producing gas on a small scale. IGas has a well at Doe Green near Warrington that is producing gas to generate electricity. Their CEO, Andrew Austin, admitted to a parliamentary select committee in March 2011 that they have fracked the well. Greenpark Energy is also engaged in fracking CBM wells in Scotland. IGas are busy drilling another well at the site and have planning permission for two more sites near Ellesmere Port and one are Barton in Cheshire. Meanwhile in Scotland Dart Energy (formerly Composite Energy) have drilled a number of wells around Airth near Falkirk and has just signed a £300 million contract to provide gas to Scotia Gas Networks. Both IGas and Dart also plan to explore for shale gas in some areas.
12 day blockade in Dec 2011 which halted CBM exploration drilling in Gloucester, New South Wales
However UK Methane, mainly in South Wales, and Greenpark Energy (now owned by Dart Energy), mainly in Yorkshire and Scotland, are also well advanced in their plans for exploiting Coal Bed Methane in those areas. In particular Greenpark has planning permission for 17 wells and a gas compressor station in Dumfries and Galloway very close to the border with England, with a number of sites with planning permission south of the border as well. UK Methane is another company with a strong interest in CBM and is particularly active in South Wales. Another player is Coastal Oil and Gas who unlike most other companies seems to be hedging its bets and is pushing both Shale Gas and Coal Bed Methane in tandem, rather than concentrating on just one at present. So far these companies have encountered close to zero resistance to their plans, partially due to clever public relations work but mainly to the fact that everyone who cares has been focused on Shale Gas. However in places where the impacts are already clear, particularly in Australia and Canada, there has been significant resistance to CBM with several successful blockades of CBM related developments. If similar levels of resistance do not soon appear in the British Isles it seems likely that we are looking at a huge expansion of CBM in the coming years with all the attendant consquences.