| Abstract |
In the town of Murska Sobata, Northeastern Slovenia, two geothermal wells -Sob 1 and Sob 2 penetrated Upper Pliocene intergranular aquifer Termal I, and some underlying Lower Pliocene aquifers. Lower Pliocene aquifers have much lower capacity than Termal I but the waters have appreciably higher content of total dissolved solids and CO2 gas. For five years since the beginning of the well operation, the content of total dissolved solids in the abstracted water was constantly decreasing, and reached less than a half of the starting value. Afterward, total dissolved solids contemporaneously increased in both wells, but at the same time, the content started to change. The changes in chemical composition closely follow the changes in hydrodynamical pressures measured in the wells with a pressure temperature gauge. In the vicinity of exploitation well, the pressures in Termal I decrease approximately every 70 minutes woing to too high pumping rate, The decrease enable more intensive incursion og waters from Lower Pliocene aquifers. When hydrodynamical pressures in Termal I recover, again the proportion of waters from the underlying aquifers decreases. When the wells were planned and also many years after the beginning of their exploitation, the differences in chemical composition of Termal I and Lower Plicocene aquifers ere unknown. Today, when the shortage with thermal water calls for reinjection into Termal I, we know that the water from Sob 1 is not suitable owing to too high content of total dissolved ions which may cause exolution of solids and cementation of interstital pores in the aquifer. |