Long-Term Pumping Test to Study the Impact of an Open-Loop Geothermal System in a Coastal Area

Compared to other European countries, there is limited use of geothermal resources in Italy for the heating and cooling of buildings (UGI-CNG, 2007). Low-temperature geothermal resources, which can be readily used for this purpose, can be found throughout Italy. The high cost and scarcity of fossil fuels have promoted the increased use of natural heat for a number of direct applications. Just as for fossil fuels, the exploitation of geothermal energy should consider its environmental impact and sustainability. Particular attention should be paid to so-called open loop geothermal systems, which use groundwater as geothermal fluid. From an economic point of view, the implementation of this kind of geothermal system is particularly attractive in coastal areas, which have generally shallow aquifers. The potential problem of seawater intrusion has led to laws that restrict the use of groundwater. The limited availability of freshwater could be a major impediment for the utilization of geothermal resources. We propose a methodology, based on an experimental approach, to characterize a coastal area in order to exploit low-enthalpy geothermal resources. A coastal karst-area near Bari, in Southern Italy, was selected for this purpose. A long-term pumping test was performed to create analog for an open-loop geothermal system. Electrical resistivity measurements were carried out, using "time-lapse" techniques, to monitor the dynamics of the freshwater-seawater interface. The results show that the pumping does not affect the quantitative and qualitative characteristics of the aquifer. The electric conductivity values suggest very limited sea water intrusion.