Abstract
AbstractThe Pannonian basin in Central Europe is well known for its rich geothermal resources. Although geothermal energy has been utilised, mainly for direct use purposes, for a long time, there are still a lot of untapped resources. This paper presents novel methods for outlining and assessing the theoretical and technical potential of partly still unknown geothermal reservoirs, based on a case study from the Dráva basin, one of the sub-basins of the Pannonian basin along the Hungarian–Croatian border. The presented methods include reservoir delineation based on combining geological bounding surfaces of the Upper Pannonian basin-fill units with a set of isotherms deriving from a conductive geothermal model. The geothermal potential of each identified reservoir was calculated by a Monte Carlo method, which was considered as being represented by the heat content of the fluids stored in the effective pore space (‘moveable fluid’). The results underline the great untapped geothermal potential of the Dráva basin, especially that of the reservoir storing thermal water of 50–75°C, which has the largest volume and the greatest stored heat content.
Highlights
The Pannonian basin in Central Europe is one of the European areas with a well-known positive geothermal anomaly, and whose rich geothermal resources have long been utilised mainly for direct use purposes
We present delineation methods for the so-called ‘basin-fill’ (BF) reservoirs storing thermal water of different temperatures which have already been applied to different parts of the Pannonian basin (Rotár-Szalkai et al, 2017), and discuss novel methods for quantifying the extractable amount of heat associated with the heat content of fluids stored in the effective pore space (i.e. ‘moveable water’)
In this very thick basin-fill complex we focused only on the Upper Pannonian – Pontian shelf front, shelf-plain, coastal plain to alluvial plain sedimentary succession (Pannonian Lake nearshore facies (BF) in Figure 2), as this is the major thermal-water bearing unit of the Dráva basin, which accumulated in an aggradational style due to the persistent high rate of subsidence coupled with an enormous rate of sediment supply
Summary
The Pannonian basin in Central Europe is one of the European areas with a well-known positive geothermal anomaly, and whose rich geothermal resources have long been utilised mainly for direct use purposes. Despite non-technical barriers (complex and time-consuming licensing processes, deficiency in capital investment), the geothermal sector in Hungary is developing fast, with an average of 10–20 new geothermal wells drilled each year. This adds to the outstandingly high number (about 980) of already existing thermal water wells in Hungary (defined in national legislation as wells with outflow temperature higher than 30°C), with a production history of often 30þ years. The number of emerging projects demands a firm geoscientific basis for assessment of the available geothermal resources, at local (project-scale) level, and at regional and even at trans-boundary scales, as co-use of the spatially extended geothermal aquifers might have serious impacts on thermal groundwater flow systems (Rman et al, 2016; Szocs et al, 2018) carrying the subsurface heat medium, especially in regions where production is extensive (e.g. southern part of the Great Hungarian Plain)
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