The paper presents a review of the geological and hydrogeological data of the Lower Cretaceous aquifer in the Polish Lowlands and discusses the possibilities for the utilisation of geothermal water resources in existing and new district heating systems. Based on experience related to the use of thermal waters in existing geothermal systems, and using data from the literature, assessments have been made of the energy and environmental effects of the application of low-enthalpy geothermal resources from the Lower Cretaceous aquifer as a source of heat for urban district heating systems. The authors concluded that the implementation of such solutions could result in the production of approximately 4 PJ of geothermal energy annually. To date, these resources have only been developed in three locations—Mszczonów, Uniejów and Poddębice—with the total amount of energy generated annually reaching 100 TJ/year. Similar district heating networks in 120 nearby localities have been also identified. Here, specified geological and hydrogeological conditions enable the extraction of heat from the investigated Lower Cretaceous aquifer, with the aim of using this for heating purposes. To achieve this goal, multiple measures are required, including the following: raising public awareness through appropriate education programmes aimed at the youngest school children; systemic, efficient energy management measures at the central, regional and local levels, and providing financial support and ensuring regulations and laws aimed at improving the development of geothermal resources.

IntroductionBorehole reconstruction involves a number of technical and research measures which ultimately result in well and reservoir conditions that enable their commercial use. In terms of geothermal needs and goals, borehole reconstruction can be carried out in three areas, i.e.:• the reconstruction of a damaged or decommissioned well; • the restoration of an existing well; • the repair of entire or part of an existing well.Further, borehole reconstruction can be complete or partial. AbstractThe beginnings of geothermal implementation research in Poland date back to 1989-1993 when the Mineral and Energy Economy Research Institute of the Polish Academy of Sciences (MEERI PAS) launched the first geothermal installation in the Podhale region, using the reconstructed Bańska IG-1 well. The knowledge acquired during these 30 years has highlighted the importance of geothermal energy-among other things, borehole reconstruction operations and the need for their further refinement. The technologies developed have been used in virtually all geothermal heating systems operating in Poland. Examples of successful reconstruction work include the Bańska IG-1 and Biały Dunajec PAN-1 wells operated by the PEC Geotermia Podhalańska S.A. geothermal company. The Mszczonów IG-1 well, which is operated by the Geotermia Mazowiecka S.A. heating company, has also undergone considerable work almost 24 years after its complete closure. Reconstruction processes can also be important in adapting existing wells for geothermal purposes. After World War II, more than 8000 boreholes deeper than 1000 m were drilled in Poland. They were primarily made for the purpose of geological surveys and hydrocarbon exploration. Some of these boreholes can be adapted for operation in geothermal systems. The paper presents selected methods of reconstructing abandoned, disused (not abandoned and not decommissioned) or damaged boreholes in order to use them in the geothermal water extraction process. Four examples of borehole reconstruction, designed and carried out with the participation of MEERI PAS in Kraków, are discussed in more detail.

Over the last few years, there has been an upsurge in the demand for drinking water and for water used in agriculture, industry, and others. Consequently, research is needed to find new technologies and methods for the comprehensive use of geothermal water sources, to provide for new resources of water. The paper shows the results of preliminary recognition in the case of the possible exploitation of the Jurassic aquifer in the Polish lowlands, considering the security of the adjacent layers. The considerations are based on experience in the exploitation of the resources of the Paris basin in France. Initial conclusions point to a high potential for such a solution, also in the Paris basin scientists are considering the use of previously unmanaged Jurassic resources.

STRESZCZENIE W obszarze niecki podhalańskiej funkcjonuje kilkanaście otworów hydrogeologicznych ujmujących wodę termalną. Jednym z nich jest otwór Chochołów PIG-1 eksploatowany na potrzeby kompleksu rekreacyjnego Chochołowskie Termy. W listopadzie 2017 roku przeprowadzono w przedmiotowym otworze badania hydrogeologiczne w celu korekty podstawowych parametrów hydrogeologicznych związanych z eksploatacją ujęcia tj. wyznaczenia jego zasobów eksploatacyjnych i dopuszczalnego obniżenia zwierciadła wód termalnych. Szczególną uwagę zwrócono na warunki wygrzewania się otworu. Wyniki przeprowadzonego pompowania pomiarowego pozwoliły głębiej poznać warunki występowania wód termalnych ujmowanych przedmiotowym otworem.

In deep geothermal boreholes, an effect of temperature (so-called thermal lift) is observed, which results in the volumetric expansion of the fluid extracted. This process results in increased wellhead pressure values being recorded; in the absence of an appropriate correction, hydraulic properties of the reservoir layer cannot be properly determined. As an example of this effect, the Chochołów PIG-1 (CH PIG-1) geothermal borehole situated in Podhale Basin in Poland was used. Hydrodynamic tests including two pumping phases were carried out in the well in order to establish the basic hydraulic properties related to the determination of its operational resources (maximum water extraction value–capacity) and permissible groundwater level. Particular attention was paid to the thermal lift effect in the borehole. The conductivity, which depends on the pumping level, could be two to three times higher with temperature correction than results without any correction. The goal was to analyse the variability of the observed physiochemical properties of the exploited geothermal waters and to determine the correlation between the properties analysed and the temperature of the geothermal water. For the relationship between temperature and the observed pressure at the wellhead, the value of the correlation coefficient was negative (a negative linear relationship was determined), which means that as the temperature increases, the wellhead pressure decreases. The hydrodynamic tests carried out in the CH PIG-1 borehole and the analysis of variability of selected ions and parameters in exploited water were necessary to assess the possibility of increasing the efficiency (Q) of the CH PIG-1 borehole and to determine the water quality and its natural variability. Such information is crucial for the functioning of the recreational complex based on the use of geothermal water. A study of the phenomena affecting the exploitation of hot water from deep boreholes enables their effective exploitation and the use of resources in accordance with the expectations of investors.