Coal Bed Methane Information
Coal Bed Methane (CBM) is ‘natural gas’ (methane) trapped in coal seams underground. To extract the gas, after drilling into the seam, it is necessary to ‘de-water’ the coal and so large amounts of water are pumped out to lower the pressure. It is often also necessary to stimulate the coal seam via fracking in order to extract the gas. There are a similar catalogue of negative environmental and social effects as with Shale Gas. This includes methane migration, toxic water contamination, air pollution, increased carbon emissions and the industrialisation of the countryside. Impacts that are specific to CBM include depletion of the water table and potentially subsidence.
In common with other unconventional gas extraction, such as Shale Gas, CBM wells do not produce large amounts of gas per well and production declines very quickly. It is therefore necessary to drill large numbers of wells, covering a huge swaths of the landscape. CBM exploitation began in the US and over 55,000 CBM well have been drilled in the last decade or so, mostly in the western states (Colorado, New Mexico and Wyoming in particular). In Australia, where it is know as Coal Seam Gas (CSG), over 5,000 CBM wells have been drilled in Queensland in the last few years and the industry is aggressively expanding into New South Wales. In the UK CBM is more advanced than Shale Gas and full scale production may begin soon if the gas companies get their way.
At Duttons Lane, Upton, Chester the CBM well will pass through approx. 750m of Sherwood Sandstone, a major aquifer in Cheshire. This will require the integrity of the well to remain impermeable to fugitive gasses and other contaminants ‘forever‘ or this aquifer could become contaminated, now or in the future.
Click this link: PEDL189_Site 10_VertSec Rev 2
Dart Energy, through their application, have applied to drill to retrieve a coal sample between the depths of 1100m – 1200m, however the CWaC Planning Permission grants the company licence to drill to a depth of 1700m – this allows the drilling company licence to drill a further 500m (1/2km) than they have requested! According to the technical, geological data (provided to the Environmental Agency by Composite/Dart Energy) in to the Bowland Shale.
As Dart Energy are a ‘data collecting’ this would appear to benefit their surveying remit.
At the Marsh Lane Farm site, Farndon, Chester the CBM well passed through approx. only 60m of Sherwood Sandstone, a major aquifer in Cheshire. Although this is only 60m in depth, this will again require the integrity of the well to remain impermeable to fugitive gasses and other contaminants ‘forever‘ or this aquifer could become contaminated, now or in the future.
Click this link: PEDL188_Site 24_Churton 1_VertSec_Rev 2
As with the Upton application, the CWaC Planning Permission granted Composite/Dart Energy licence to drill to a depth of 1700m even though the application document states that the drilling company wished to drill to between 680 – 800m only o retrieve a core sample of coal. Hence, CWaC gave permission for Dart Energy to drill to over twice as deep as they requested in their planning application; if they wished.
Why the drilling company have been allowed permission to drill down further than they have requested is a question as yet unanswered by the CWaC council to date.