Recognition of Lower Cretaceous geothermal potential of Central Poland with the application of geophysical methods

In Poland, geothermal energy and waters are utilized in several geothermal plants as well as in balneological and recreation centers. The research projects run in last years aimed to recognize the geothermal potential in various regions of Poland. These projects were especially focused on selection of sites prospective for development of geothermal resources. For this purpose, various integrated exploration methods were applied to reduce the geological risk, which affects any design of geothermal installation. Among the convenient exploration tools are geophysical methods widely applied to the recognition of geological structure of the Earth and to petroleum exploration. Taking into account the Malanow area located in the Mogilno-od Trough (central part of the Polish Lowlands), the authors present the opportunities provided by the usage of archival geophysical data for characterization of geothermal aquifer. The results demonstrate that geophysical methods can effectively support the selection of areas favorable for future geothermal investments. Simultaneously, such methods can be useful in determination of hydrogeothermal parameters of particular aquifer. In the study area, local depressions of the top surface of geothermal aquifer are known, which can be identified with the seismic data. Moreover, seismic inversion can be applied to porosity estimations of Lower Cretaceous aquifer. The most favorable reservoir properties occur in the NE part of the study area where the top surface of Lower Cretaceous formation is located at <1500 m depth and in its marginal parts where this surface drops down to even 1900 m depth. Seismic data also indicate that the Lower Cretaceous aquifer remains tectonically undisturbed.