Fingerprinting coal-derived gases from the UK

Györe, D. , McKavney, R., Gilfillan, S. M.V. and Stuart, F. M. (2018) Fingerprinting coal-derived gases from the UK. Chemical Geology, 480, pp. 75-85. (doi: 10.1016/j.chemgeo.2017.09.016)

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The large-scale extraction of unconventional hydrocarbons in the United States has led to fears of methane contamination of shallow groundwaters. Differentiating between the deep gas released during extraction (shale gas, coal bed methane and underground coal gasification) and natural shallow-sourced methane is imperative for the monitoring and managing of environmental risks related to the extraction process. Here, for the first time, we present measurements of the major gas, and stable and noble gas isotope composition of coal bed methane (CBM) from central Scotland and coal mine methane (CMM) from central England, UK. The molecular (C1/(C2+C3) = 21 to 120) and stable isotope compositions (δ13CCH4 = -39.5 to -51.1‰; δDCH4 = -163 to -238‰) indicate a thermogenic origin for the methane. They are distinct from the majority of shallow-sourced gases in UK. Both sample suites exhibit high He concentrations (338 to 2980 ppmv) that are considerably above atmospheric and groundwater levels. Simple modelling shows that these high 4He concentrations cannot be solely derived from in situ production since coal deposition, and hence the majority is derived from the surrounding crust. The Scottish CBM contains a resolvable mantle He, Ne and Ar contribution that may originate from melts in the deep crust, demonstrating the UK coals have acted as a store for deep volatiles for 10s of millions of years. The high 4He in the coal-derived gases has the potential to be used as a novel diagnostic fingerprint to track fugitive release of deep methane from future unconventional gas extraction operations in the UK.

Item Type:Articles
Additional Information:The research present was funded by a Natural Environmental Research Council (NERC) 407 grant to Gilfillan and Stuart (NE/L008475/1).
Glasgow Author(s) Enlighten ID:Gyore, Dr Domokos and Stuart, Professor Fin
Authors: Györe, D., McKavney, R., Gilfillan, S. M.V., and Stuart, F. M.
Subjects:Q Science > QE Geology
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Chemical Geology
ISSN (Online):1872-6836
Published Online:14 September 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Chemical Geology 480:75-85
Publisher Policy:Reproduced under a Creative Commons License

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