The use of magnetotelluric and gravity studies to identify geothermal conditions – case study from the Polish Lowlands

Geothermal potential in Poland is mostly associates with low-temperature resources accumulated in four geothermal provinces: Polish Lowlands, Carpathians, Carpathians Foredeep and Sudetes Region. Each provinces is characterized by different geological, and geothermal parameters, determination of which can be supported by magnetotelluric and gravimetric data. Magnetotelluric methods are frequently used as auxiliary under Polish conditions predominant by geothermal resources associated with sedimentary complexes and predominantly in resources connected with crystalline rocks, where seismic method is not effective. Gravimetric methods are used to identify deep and shallow fault zones, which may correspond to geothermal hotspots.

The paper presents examples of hydrogeothermal investigation supported by those two methods in Jurassic sedimentary complexes of Polish Lowlands. The results clearly shows that magnetotelluric and gravimetric methods can effectively support the selection of perspective areas for future low-temperature geothermal investments.

An integrated interpretation of magnetotelluric, gravimetric and seismic results (where available) in the exploration area, supported by existing hydrogeological data, improves the reliability of conceptual models of geothermal systems in the Polish Lowlands by reducing interpretational ambiguity. Comprehensive interpretation helps to distinguish conductive zones related to saline aquifers from structural features controlling fluid circulation, such as fault and fracture zones. This approach reduces exploration risk at the early stage of project development by narrowing the target area for detailed surveys and by constraining the location and expected depth of exploratory wells. In practice, the proposed workflow can be used as a cost-effective screening tool to identify the most promising sites for low-temperature geothermal heat production.