Methane occurs naturally in the atmosphere and is commonly found at trace levels as a dissolved component of groundwater. Methane is also released by human activity and is an important greenhouse gas.
We are surveying the current distribution of methane concentrations in UK groundwater, focussing on areas where aquifers are underlain by shale units that may be exploited for shale gas. The National Methane Baseline dataset will be a reference point against which any future changes in groundwater methane concentrations can be measured. It will be of particular interest to researchers and environmental regulators.
The results page provides a summary of the methane baseline results up to January 2015 and links to the regional summaries.
Understanding the current distribution of methane in UK groundwaters will provide a baseline against which any future changes can be measured. This has become particularly important with increasing interest in shale gas in the UK.
Evidence from the USA has shown very high methane concentrations in some aquifers in some areas where shales are being commercially exploited for gas. However, there is considerable uncertainty and argument over the source(s) of methane and how it has entered the aquifers.
Crucially, there are no consistent baseline data on methane concentrations in groundwater in the USA collected before shale gas exploitation began, which makes it very difficult to assess and deal with the observed problems of methane in groundwater.
The need for a methane baseline in the UK was recognised in the 2012 report on shale gas extraction published by the Royal Society and Royal Academy of Engineering 7.9 MB pdf.
In the UK, BGS scientists are building on our previous work and measuring methane concentrations in groundwater in a range of aquifers before any shale gas development gets underway. This will provide a baseline against which any future environmental changes can be assessed, and will enable informed management decisions to be taken.
The methane baseline is therefore defined for this project as the current background range of methane concentrations in UK groundwaters before any significant exploitation of unconventional hydrocarbons, such as shale gas, takes place.
The measured methane may not necessarily originate naturally from geological sources — in some cases it may have been produced or released because of human activities such as coal mining or landfill operations.
Collecting groundwater samples for methane analysis is straightforward, providing certain precautions are undertaken.
To get an accurate concentration measurement, groundwater has to be sampled before it comes into contact with air so that no gas can escape. This means collecting a sample directly from a pumped borehole, by attaching a hose with an airtight connection at the top of the borehole before the pumped water enters a storage tank or is treated in any way.
Special containers are used to preserve the sample until it reaches the laboratory. In addition to sampling for dissolved methane, a number of chemical parameters are measured in the field (eg groundwater temperature, dissolved oxygen and redox potential) and samples are collected for laboratory analysis of a broader range of chemical parameters.
Other web pages provide further information on the UK baseline groundwater chemistry programme.
To find suitable boreholes, BGS greatly appreciates the support provided by the Environment Agency, Natural Resources Wales, water utilities and other private borehole owners such as farms and golf courses.
Summary results from the survey (up to January 2015) and summary of existing data.
Methane data from previous BGS water quality surveys have been published in papers and reports that are available from the NERC Open Research Archive (NORA). The references are given below. Please note that a small amount of data from these published sources has not been used in the statistical summaries for the regions presented in the accompanying web pages because they were considered not to represent typical baseline conditions.
Gooddy, D, and Darling, W G. 2005. The potential for methane emissions from groundwaters of the UK. Science of the Total Environment, 339. 117–126. http://dx.doi.org/10.1016/j.scitotenv.2004.07.019
Darling, W G, and Gooddy, D C. 2006. The hydrogeochemistry of methane : evidence from English groundwaters. Chemical Geology, 229 (4). 293–312. http://dx.doi.org/10.1016/j.chemgeo.2005.11.003
Ó Dochartaigh, B E, Smedley, P L, MacDonald, A M, Darling, W G, and Homoncik, S. 2011. Baseline Scotland: groundwater chemistry of the Carboniferous sedimentary aquifers of the Midland Valley. British Geological Survey Open Report OR/11/021. 91pp.
Contact Dr George Darling for further information.