Questions and answers when preparing to implement a geothermal concession

Abstract

Hungary has favorable conditions due to its high geothermal gradient, but most domestic utilization is at lower temperatures. However, there are also high-enthalpy reservoirs in the country. High-enthalpy geothermal energy refers to the utilization of the Earth’s internal heat in system where the extractable fluid (water or steam) is at high temperature and pressure. High-enthalpy temperatures above 150°C. According to theoretical considerations, there are high-enthalpy Mesozoic-Paleozoic basement reservoirs of the Pannonian Basin, at a deeper level (4-5 km). The water/steam blowout of the Fabiánsebestyén-4 borehole provided spectacular practical support for this view. The Fábiánsebestyén-4 deep borehole revealed a high-enthalpy geothermal reservoir in the basement of the Pannonian Basin. The energy-carrying fluid is superheated saline water, the pressure of which is much higher than hydrostatic one. The reservoir is located entirely in the fractured-cracked basin basement. The fractured structure of the reservoir was significantly created by tectonic effects and a local “push-up” process belonging to a lateral displacement zone. The natural hydraulic fracture system generated by the over-pressured marl assemblage may be significant. Hungary’s largely untapped high-enthalpy geothermal energy reserves enable the establishment of electricity-generating geothermal system. The utilization of high-enthalpy geothermal energy focuses on subsurface outcrops discovered during domestic structural and hydrocarbon exploration.