Review of geothermal conditions of Hungary

Abstract

The heat flow map of Hungary was presented in the Atlas of Geothermal Resources in Europe in 2002 and was last updated in 2005. Since that time several geothermal projects, e.g. TransEnergy (2010-13), assessment of the geothermal potential of the Drava basin (2013) Paks-II, NPP (2016) and continuous drilling activity in the country have been in progress. Large amount of temperature data became available, which allowed the update of the Geothermal Database of Hungary and the compilation of an updated heat flow map and temperature maps.
 The heat flow is determined based on the Fourier law using the thermal conductivities of rocks and temperature gradient calculated from temperature observations in boreholes and wells. The thermal conductivity is known from laboratory measurements made on core samples. The thermal conductivities and the temperature data are stored in the Geothermal Database of Hungary.
 The heat flow is calculated in 2001 boreholes and wells using the Bullard-plot technique. The mean heat flow in Hungary is 90 mW/m2, varying between 30 mW/m2 and 120 mW/m2. The high values are found over buried basement highs in the eastern and southern part of the country, while the low values are located in the recharge areas of karstic flow systems. In the sedimentary basins, where the thickness of the Neogene and Quaternary sediments reaches 5-7 km, the heat flow is slightly below the mean value (80-90 mW/m2) due to the cooling effect of sedimentation. These basins contain the main thermal water aquifer in Hungary utilized for district heating and green house heating. The buried basement highs characterized by high heat flow (100-120 mW/m2) are potential sites to create artificial geothermal reservoirs by hydraulic fracturing (EGS).
 Temperature maps at 500 m, 1 km, 2 km and 3 km depths were also compiled. Similarly to the heat flow, the temperature anomalies strongly reflect the local and regional groundwater flow systems.

Multimethodological Revisit of the Surface Water and Groundwater Interaction in the Balaton Highland Region—Implications for the Overlooked Groundwater Component of Lake Balaton, Hungary

“…The simulated temperature field was in accordance with the published temperature maps based on well data: 500 m below the surface, the average temperature was 20-30 • C, and 1000 m below the surface, temperatures of 40-50 • C were reported for the study area [124]. Groundwater flow is responsible for the region's temperature anomalies [126,127].…”

“…The bottom of the numerical model was an artificial undulating surface where a no-flow boundary condition was set. The heat transport simulation was run with the following boundary conditions: annual mean air temperature (11 • C) along the surface (after Péczely [123]), a constant heat flow of 55 mW/m 2 at the bottom (based on Lenkey et al [124]) and symmetry on the lateral boundaries, meaning that the temperature gradient across these boundaries was zero (Figure 9d). The model was discretised by triangular and non-uniform finite elements using a maximum element size of 50 m within the model domain and 25 m along all the inner and external boundaries.…”

Lithospheric Structure of the Circum‐Pannonian Region Imaged by S‐To‐P Receiver Functions

“…The depth of the negative phase is 45 km; this station is located in southwestern Hungary (in Great Hungarian Plain), where the heat flow is the highest (ca. 110 mW/m 2 based on Lenkey et al., 2002, 2021) and the lithosphere is the thinnest beneath the investigated area. The figure also presents the theory of the uncertainty calculation, which is based on Abt et al.…”

“…On all three maps, the NPD correlates well with the LAB depth beneath the Great Hungarian Plain. This area is characterized by a thin lithosphere, associated with high surface heat flow (>90 mW/m 2 , Lenkey et al., 2021). In the areas where the lithosphere is thicker and the surface heat flow is lower (<70 mW/m 2 ), NPD values obtained from 2D CCP migration are less likely consistent with the LAB, but is probably indicative of another shallower intra‐lithospheric discontinuity.…”

Municipal Geothermal Systems: Evaluation of Three Hungarian Cases

“…This article focuses on the challenges faced, based on recently gained experiences of installed geothermal systems. All systems are in the southeastern part of Hungary, which has a very good geothermal potential [26]- [29] with high geothermal gradients (approximately 50 °C/km) [30]. Altogether, three municipal geothermal systems are involved in the investigation, each with different characteristics, but to some extent facing similar difficulties.…”