Development of a Methodology for Estimating Methane Emissions from Abandoned Coal Mines in the UK

Abstract:

The principal aim of the project was to produce a verifiable methodology for generating accurate and reliable estimates of methane emissions from abandoned mines in the UK, to be considered for inclusion in the UK greenhouse gas inventory.

The prime drivers for methane emission from abandoned mines are displacement by rising mine waters and the rate of emission of methane from the coal seams in the strata disturbed by mining. Rising mine water also serves to isolate methane reserves by cutting them off by flooding. The UK coalfields have been modelled to obtain estimates of water inflow and methane reserves within the coalfields. Measurements have also been made on methane emissions from mines, either from vents or from more general diffuse emissions from the surface. The general methodology has been to seek a relationship between the measured methane flows and parameters relating to the water and gas in the underlying abandoned workings

No suitable relationship was found between vent methane flow data and the water flow in the underlying abandoned workings. However, vent methane flow data did show an increase with the size of the underlying methane reserve in the abandoned workings. Flux data from the diffuse monitoring was converted into flows by multiplying by the area of underlying workings. These flows also showed an increase with underlying gas reserve. The data was scattered in both sets, but the gradients of regression lines through the flux data was within 11% of the vent flow data. Consequently the two data sets were combined and a regression provided a gradient equivalent to an emission of 0.74% of the underlying gas reserve per year.

1. Introdution
2. General Methodology
3. Sources of Data
4. Mine Water Recovery
5. Mine Water Recovery Modelling
6. Methane in Mines
7. Monitoring of Methane at Surface Vents
8. Monitoring of Diffuse Methane Emissions
9. Methane Reserve Modelling
10. Methodology for Estimating UK Emissions
11. Results
12. Conclusions
13. Recommendations
14. Acknowledgements

• Appendix A - Report uses as source data for study
• Appendix B - Map of coalified areas and zones
• Appendix C - List of coal authority monitoring sites and pumping sites
• Appendix D - Sites of recorded surface gravity discharges of mine water
• Appendix E - Average permeabilities used for modelling coalfields
• Appendix F - Direct measurement of methane flux on one day campaign
• Appendix G - Background to the reserve modelling method
• Appendix H - Reserve estimates by coalfield area and year

Publication Year:

2005

Publisher:

Department for Environment, Food & Rural Affairs

DOI:

No DOI minted

Author(s):

Kershaw, S.