This article presents the results of numerical modeling for a hypothetical CO₂-EGS system in the volcanic rocks of the Gorzów Block, Poland. Modeling was carried out in the following stages: in phase 0, modeling of the fracturing process was performed, as a result of which the permeability distribution for the newly created fractured zone was obtained. Next, the process of saturating the EGS reservoir with CO₂ was modeled until pure CO₂ could enter the production well (phase 1). Then, a multi-variant simulation of heat production was performed (phase 2). The obtained results allowed for drawing interesting conclusions: (1) the duration of phase 1 may take several years unless a sufficiently high injection rate of CO₂ is supplied, (2) the higher the injection rate of CO₂, the lower the cumulative storage ratio of CO₂, and (3) most of the CO₂ storage in the formation takes place in phase 1, while even 92% of the CO₂ injected in phase 2 can be recovered via the production well. Despite the environmental benefits connected with structural trapping of CO₂, the Gorzów Block has probably too low formation temperature (145 °C) and too low stimulated volume (~0.1 km³) to deliver satisfactory and stable thermal output.

The principle of Enhanced Geothermal System (EGS) technology is that water injected at a sufficiently high pressure will lead to the fracturing of naturally impermeable rocks, and as a result, this will create hydraulic communication between wells. In this way, reservoirs not previously considered to be perspective can provide geothermal heat to the surface. Since nearly two decades, CO2 is considered, mostly theoretically, as a working fluid that can potentially provide higher net power output than water in EGS’s installation. In this respect, the possibility of accessing high-temperature heat from the Åre and Tilje formations located on the shelf of the Norwegian Sea was analysed. The estimated temperature at the reservoir depth of 4,500–5,000 m is not less than 165°C. For this, a 3D numerical modelling was performed in order to analyse 10 different scenarios for heat extraction using supercritical CO2 (sCO2) as a working fluid. Results indicate that appropriate matching of the mass flow and temperature of the injected CO2 allows to avoid premature temperature decline in the reservoir. However, as Åre and Tilje formations are built from highly porous and relatively highly permeable rocks, the fluid entering the production well will always be a mixture of CO2 and water. This is advantageous from the point of view that a significant part of the injected CO2 is trapped in the reservoir, while the higher water content in the production well allows a significant temperature drop during fluid extraction to the surface to be avoided.

The article presents the possibility of utilising the available potential of the main geothermal reservoirs in Poland, i.e. the Lower Jurassic and Lower Cretaceous, by using the existing infrastructure in the form of still-operating district heating networks. The suggested solution, therefore integrates the resource side with the infrastructure side. This approach should significantly accelerate the implementation of the proposed solutions, supporting the achievement of the ambitious objectives of Poland’s Energy Policy 2040. Geothermal resources in Poland are characterised by low enthalpy and low temperature. Their temperature is often too low for direct utilisation in systems relying solely on geothermal energy. Existing district heating networks require significantly higher heating medium temperatures during specific periods (when low ambient air temperature is observed). Using existing boilers as peak energy sources while employing geothermal energy as the base load for meeting annual heating demands appears to be an attractive and feasible technical option. Poland, alongside Denmark, Latvia, Finland, Estonia, and Lithuania, is among the countries with the highest density of district heating networks. These networks serve as invaluable infrastructure, reducing the costs associated with geothermal energy extraction. However, this infrastructure is under real threat from the trend towards decentralised energy systems. The liquidation of district heating networks would be irreversible, further exacerbated by the lack of access to clean and alternative energy carriers to replace fossil fuels. It has been demonstrated that, in most analysed cases, the combination of available geothermal resources and district heating infrastructure can successfully contribute to achieving the assumed goals of Poland’s Energy Policy. In the best locations, the share of renewable energy exceeded 80%, with an average of around 50%. The total reduction of CO2 emissions is estimated as 1.16 million tonnes yearly. The article draws attention to the slow but positive change in the electricity mix, in which the share of RES is growing. This trend is extremely beneficial for popularising heat pumps powered by electricity using geothermal resources as a low-temperature energy carrier.