Geophysical investigations using seismic reflection method in the area with the geothermal waters

Reflection seismic investigations in the „Podlog-Banja“ geothermal field are the first investigations of this kind planned to perform „pilot“ doublet-system for using of geothermal energy in the Republic of Macedonia. The selection of the “Podlog–Banja” geothermal field for the installation of a pilot doublet system was based on its favourable geothermal characteristics and the availability of an established team of qualified experts who could manage, monitor and operate the system effectively. Reflection seismic surveys were conducted within a metamorphic rock complex overlain by sedimentary and volcano-sedimentary formations with a thickness of approximately 300–500 m. Under such geological conditions, the quality of the seismic reflection data is expected to be lower than that typically achieved in geological environments characterised by horizontal layers. The effectiveness of the studies is further limited by the inclined spatial orientation of the geological structures and the low seismic velocity contrasts among the lithological units in the investigated metamorphic complex. These factors reduce the resolution and interpretability of the acquired seismic data. Due to the inclined spatial orientation of the geological units, the litho-spaces identified through reflection seismic investigations have not been adequately documented by previous drilling activities within the “Podlog–Banja” geothermal field. As a result, the litho-physical interpretation of the reflection seismic results should therefore be regarded as “forecasting”.