Closing of hard coal mines, especially stopping the process of mine water
pumping, results in a reconstructionof the Carboniferous water-bearing horizon, leading to the intensification of gas flux to the near-surface zone („piston effect”). Stopping the fans considerably enhances the movement of mine gases towards the surface in closed mines. Stopping the fans results in an accumulation of gases in workings and old workings.
The results of geochemical analyses performed in the area of the hard coal mine „Niwka-Modrzejów” are presented in the paper. The obtained results and their comparison with the existing geological-reservoir model prove that the intensification of the mine gases flow towards the surface continues through the zones of tectonic discontinuities, crackings, and loosened zones in the Upper- Carboniferous sedimentary rocks. The thickness and lithology of the onlying overburden plays a decisive role in the limitation of the mine gases migration.