Dynamic elastic properties, petrophysical parameters and brittleness of hot dry rocks from prospective areas of Central Europe

Enhanced geothermal systems in hot dry rocks are among the most promising sources of green renewable energy, with increasing interest in Central and Eastern Europe. The effective implementation of enhanced geothermal systems in new areas is based on the use of insights from ongoing projects, particularly in the study of petrophysical properties and reservoir stimulation technologies. This study aimed to characterize hot dry rocks in Central Europe by analyzing permeability, porosity, mineral composition, elastic properties, and brittleness index to assess their susceptibility to hydraulic fracturing. Drill core samples were collected from three formations: granites from the Karkonosze Mountains, volcanic rocks from the Gorzów Block, and tight sandstones from the Mogilno-Łódź Trough. The results indicated that the petrophysical properties and mineral compositions of these rocks are comparable to the corresponding Western European formations. Altered granites and some volcanic rocks showed significant decreases in wave velocities compared to intact samples, while sedimentary formation exhibited lower elastic moduli, indicating less favorable conditions for the development of the fracture network. Dynamic elastic tests suggested that brittleness index interpretation should differ between sedimentary and igneous hot dry rocks. In sedimentary formations, high brittleness index values indicate zones with elevated potential for complex fracture networks, aligning with the classic brittleness index concept. On the contrary, in igneous formations, low brittleness index values indicate zones of alteration and well-developed natural fractures, which are beneficial for hydroshearing stimulation. Document Type: Original article Cited as: Moska, R., Labus, K., Kasza, P. Dynamic elastic properties, petrophysical parameters and brittleness of hot dry rocks from prospective areas of Central Europe. Advances in Geo-Energy Research, 2024, 14(2): 90-105. https://doi.org/10.46690/ager.2024.11.03