Major geothermal energy potential uncovered near Zagreb

(Photo: Agencije za ugljikovodike)

A significant geothermal energy breakthrough has been confirmed near Zagreb, marking another step forward in Croatia’s energy transition and ambitions for greater energy independence.

The town of Zaprešić has successfully completed a major geothermal exploration project led by the Agencija za ugljikovodike (Croatian Hydrocarbons Agency).

The project, titled Preparation and Exploration of Geothermal Potential in the Context of Centralised Heating, has delivered exceptional results, Večernji list reports.

Zaprešić is now the fourth Croatian location, following Velika Gorica, Osijek and Vinkovci, where successful exploration and drilling have confirmed substantial geothermal resources.

Outstanding Results at 1,600 Metres Depth

The Zaprešić well was drilled to a depth exceeding 1,600 metres and has demonstrated remarkable performance. According to Marijan Krpan, Director of the Croatian Hydrocarbons Agency, the well currently produces 37 litres of geothermal water per second, with a bottom-hole temperature of 95°C.

“The permeability of the reservoir is enormous. This single well is sufficient to meet all of the thermal energy needs of the town of Zaprešić,” Krpan stated.

Marijan Krpan (Photo: Agencije za ugljikovodike)

Importantly, positive results were recorded at all four exploration sites. Experts from the Agency had accurately assessed the geothermal potential at each location prior to drilling, underlining the technical expertise behind the project.

Key Role in Croatia’s Energy Transition

Krpan emphasised that geothermal energy could become a cornerstone of Croatia’s energy transition. Unlike fossil fuels, geothermal energy provides a stable and sustainable source of heat, contributing to lower emissions and long-term energy security.

He added that Croatia possesses the scientific expertise, technical capacity and operational experience to carry out complex exploratory works and accurately assess geothermal potential.

Notably, the Zaprešić location initially presented the highest exploration risk, as it had the least existing geophysical and drilling data. Its success therefore represents a significant technical achievement.

Next Steps: Injection Wells and Expansion Across the Pannonian Basin

The next phase of development includes the drilling of injection wells at all four confirmed sites, a crucial step in establishing full geothermal heating systems.

Further exploration is planned across Croatia’s section of the Pannonian Basin, an area believed to hold exceptional geothermal resources. Krpan suggested that the scale of potential could position Croatia as an important player in the geothermal energy sector.

There are also ambitions to export Croatian expertise abroad, with Kazakhstan identified as a potential future partner for geothermal development projects.

Commercial Use Possible by 2028

Commercial operation of the four wells will depend on decisions taken by local authorities in the municipalities where they are located. However, Krpan believes the Zaprešić system could be operational by 2028.

Zaprešić Mayor Željko Turk welcomed the results, highlighting that the well is located within the urban area and provides a strong foundation for future investment.

Plans are already underway to connect a significant portion of the district heating network to the new geothermal system. Several major development projects are located nearby, including a new school, a city swimming pool complex just 700 metres from the site, and a business zone.

The mayor stressed that the project offers strong economic opportunities, lower energy costs for residents and businesses, and supports the shift away from fossil fuels.

Marijan Krpan, Martina Tuschl, Željko Turk (Photo: Agencije za ugljikovodike)

€50.8 Million Investment

The geothermal exploration project was financed through Croatia’s National Recovery and Resilience Plan, with a total value of €50.8 million.

Exploration and drilling works were carried out by CROSCO, a member of the INA Grupa, while the Croatian Hydrocarbons Agency provided expert leadership and supervision.