In the last decade, exploration for unconventional hydrocarbon (shale gas) reservoirs has been carried out in Poland. The drilling of wells in prospective shale gas areas supplies numerous physicochemical measurements from rock and reservoir fluid samples. The objective of this paper is to present the method that has been developed for finding similarities between individual geological structures in terms of their hydrocarbon generation properties and hydrocarbon resources. The measurements and geochemical investigations of six wells located in the Ordovician, Silurian, and Cambrian formations of the Polish part of the East European Platform are used. Cluster analysis is used to compare and classify objects described by multiple attributes. The focus is on the issue of generating clusters that group samples within the gas, condensate, and oil windows. The vitrinite reflectance value (R_o) is adopted as the criterion for classifying individual samples into the respective windows. An additional issue was determining other characteristic geochemical properties of the samples classified into the selected clusters. Two variants of cluster analysis are applied—the furthest neighbor method and Ward’s method—which resulted in 10 and 11 clusters, respectively. Particular attention was paid to the mean Ro values (within each cluster), allowing the classification of samples from a given cluster into one of the windows (gas, condensate, or oil). Using these methods, the samples were effectively classified into individual windows, and their percentage share within the Silurian, Ordovician, and Cambrian units is determined.

A paleokarst system developed in the Upper Jurassic–Lower Cretaceous carbonate complex has been recognized in the Carpathian Foreland area. Well logs testing and core data as well as an acoustic imager, a microresistivity scanner and six-arm dipmeter images were used to identify and analyze the character of the paleokarst features. A detailed interpretation of microresistivity and acoustic image logs allowed for the identification of different types of karst forms, such as caverns; multidirectional fractures, including fractures widened by dissolution; and the type of sediments filling them. The analysis of the seismic survey was conducted by linking the paleokarst characteristic features recognized in the seismic image to the karst intervals determined from borehole data. The set of seismic attributes calculated from the analyzed 3D seismic data, including the RMS amplitude, instantaneous frequency, consistent dip, variance, sweetness and relative acoustic impedance, helped to delineate the zones of the paleokarst distribution. Within the interpreted paleokarst surface developed in the carbonate formations in the study area, there are sinkholes, limestone pavements and valleys. Furthermore, in the northwestern part of the analyzed area, the development of paleokarst forms is related to the presence of a relatively deep branch of a paleovalley formed in the Paleogene, as well as to numerous discontinuities developed in carbonate formations. The development of this type of larger karst form was probably controlled primarily by tectonic faults. The research conducted by the authors of this paper showed the widespread presence of paleokarst features in Upper Jurassic–Lower Cretaceous carbonate formations in the study area. A good spatial identification of the paleokarst surface can be important in a regional context, since the highest part of the profile of carbonate formations is the most important reservoir for geothermal or hydrocarbon resources in this region.

The European Union’s climate policy promotes waste incineration as an alternative to landfilling. However, the continuous nature of waste generation, combined with seasonal variability in energy demand, leads to a mismatch between heat production and consumption in waste-to-energy systems. Seasonal Borehole Thermal Energy Storage (BTES) systems are one option for mitigating this mismatch. The aim of this study was to develop a theoretical geological model of a BTES-type storage system located in the Carpathian Foredeep and to simulate its multi-year operation using the FEFLOW numerical modeling software. The model represents an initial assessment of system performance under assumed geological and operational conditions and has not yet been validated against field measurements. Two operating scenarios were analyzed. In the 1st scenario, both heat injection and heat extraction from the storage system occurred through Borehole Heat Exchangers (BHEs) located in the center of the storage system. In the 2nd scenario, heat extraction is initiated through heat exchangers located in the outermost zone of the BTES field. The analysis focused on the temperature of the circulating working fluid in the U-tubes and on variations in heat transfer rate during injection and extraction cycles. The energy performance of the system was evaluated for both configurations. The results showed that the reversed-flow operating strategy provided a higher thermal energy recovery ratio and more favorable long-term thermal performance than the center-to-center flow configuration, indicating the potential feasibility of BTES operation under the assumed Carpathian Foredeep conditions.