Abstract
Natural gas extraction from shale rock necessitates hydraulic fracturing of rocks, which involves large amounts of fracture fluids made of 90.5% of water. The authors focus on feasibility of groundwater abstraction for the purpose of applying fracture fluids in wells of the Lublin Basin - area of perspective unconventional gas exploitation from the Ordovician and the Silurian shales. These data refer to the expected specific capacity of wells abstracting groundwater from main useful aquifers. Specific capacity of a well (q) belongs to high-certainty empirical parameters, characterizing water-bearing capacity of rocks at a regional scale. The spatial evaluation of q was based on respective data coming from 7 sheets of the Hydrogeological Map of Poland (scale 1:200,000) covering research area. Specific capacity q was calculated for wells abstracting water from the Upper Cretaceous, Tertiary and Quaternary aquifers in areas presented on particular sheets of the map. Authors determined the variability distribution and the cumulative probability plots of q values, indicating a range which corresponded to a sum of standard deviation (SD) above and below median (X̄), i.e. X̄ ± 1SD. On the total the interval included 68.2% of data. The results reveal that 0.6 ≤ q ≤ 40 m3h-1 per 1 meter of drawdown for the Upper Cretaceous rocks in the eastern part of the area, and 1.1 ≤ q ≤ 110 m3h-1 per 1 meter in the western part, being a result of more intense fracturing and fissuring. Owing to the scarcity of data, q values of wells screened at the Tertiary and Quaternary aquifers are given jointly for the whole area: 0.8 ≤ q ≤ 20 and 1.0 ≤ q ≤ 10 m3h-1 per 1 meter, respectively. The obtained specific capacities are high. When the wells are properly designed, their discharges may reach about ca. 100 m3h-1.
