Drilling for Coal Bed Methane

As opposed to extracting gas from working mines, Coal Bed Methane specifically exploits natural gases from unworked coal seams. Often called Virgin Coal Bed Methane (VCBM), the process involves drilling directly into the unworked coal.

The way of determining whether or not gas is present in the coal, and can be produced commercially - varies from site to site. Indeed, studies have found that every coal seam is different in its characteristics. Essentially, the detailed appraisal process involves pumping water away from the coal seam, with the water saturation of the seam being a key factor in determining the viability.

Coal Bed Methane production in the UK

The first Coal Bed Methane well in the UK was drilled in 1992 and there have since been several pilot drilling schemes across the country. Despite this, there are no large scale operational developments yet. In a handful of areas commercial operators appear close to achieving commercial-scale drilling with the help of directional drilling techniques, adopted from the oil industry.

UK Government figures indicate that the best Virgin Coal Bed Methane prospects lie in coal seams thicker than 0.4m at depths between 200m and 1200m. Currently, low permeability and high drilling costs make deeper targets unattractive. Good prospects should have methane levels of >7m3/tonne. However, permeability, rather than seam gas content, is thought to be the most critical factor.

Elsewhere, because exploration and production companies are obliged by the UK Government to maximise the recovery of any hydrocarbon reserve they are given a licence for, new attention is being paid to Enhanced Coal Bed Methane (ECBM) techniques. In the future, these could see initiatives such as CO₂ storage - where CO₂ is injected into the coal thereby displacing methane and the CO₂ remains locked away underground.

The Future

The successful use of Coal Bed Methane in the US is undoubtedly an inspiration for other countries around the world to develop similar energy resources. However, the widely varying characteristics of coal seams and the detailed appraisal processes involved will ensure steady, rather than speedy, progress. New technologies in the extraction of methane from coal, notably at shallower depths in Australia, may prove to be useful in the UK. In addition, there are hopes that new technologies will soon allow mining operators to extract from the very large deep coal resources in the UK.

Please also see our introduction to Coal Bed Methane.