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Criteria of Gas Hazard Assessment in the Areas of Closed Mines of the Wałbrzych Coal District, Southwestern Poland
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Near Surface 2006 - 12th EAGE European Meeting of Environmental and Engineering Geophysics, Sep 2006, cp-14-00042
- ISBN: 978-90-73781-62-7
Abstract
The mine closures in the Wałbrzych Coal District, and particularly the cessation of drainage, resulted in the recovery of the groundwater table in Carboniferous multi-aquifer system which, in turn, intensified the flux of coalbed gases into the near-surface zone. <br>Surface geochemical surveys run in the years 1997-2001 and 2004-2005 in the Wałbrzych District demonstrated general increase in methane (up to maximum 49.6 vol. %) and carbon dioxide (up to maximum 17.4 vol. %) concentrations in soil gas samples collected at depth down to 2 m. The forced influx of methane and carbon dioxide into the near-surface zone measured with the modified, static chmaber method was up to 620 dm3/m2h i 330 dm3/m2h, respectively. Studies on coalbed methane and carbon dioxide flux to the near-surface zone supported by geochemical, geological and mining-engineering criteria, enabled the determination of a three-degree scale of near-surface gas hazard. Recognition of gas hazard mechanisms in the near-surface zone of post-mining areas is significant for restructuring of the mining industry in Poland and prediction of gas hazard caused by coal mine closure.