Pleistocene alkaline basaltic lavas crop out in the region of Volos at the localities of Microthives and Porphyrio. Results from detailed petrographic study show porphyritic textures with varying porosity between 15% and 23%. Data from deep and shallow water samples were analysed and belong to the Ca-Mg-Na-HCO₃-Cl and the Ca-Mg-HCO₃ hydrochemical types. Irrigation wells have provided groundwater temperatures reaching up to ~30 °C. Water samples obtained from depths ranging between 170 and 250 m. The enhanced temperature of the groundwater is provided by a recent-inactive magmatic heating source. Comparable temperatures are also recorded in adjacent regions in which basalts of similar composition and age crop out. Estimations based on our findings indicate that basaltic rocks from the region of Volos have the appropriate physicochemical properties for the implementation of a financially feasible CO₂ capture and storage scenario. Their silica-undersaturated alkaline composition, the abundance of Ca-bearing minerals, low alteration grade, and high porosity provide significant advantages for CO₂ mineral carbonation. Preliminary calculations suggest that potential pilot projects at the Microthives and Porphyrio basaltic formations can store 64,800 and 21,600 tons of CO₂, respectively.

Underground geological energy and CO₂ storage contribute to mitigation of anthropogenic greenhouse-gas emissions and climate change effects. The present study aims to present specific underground energy and CO₂ storage sites in Greece. Thermal capacity calculations from twenty-two studied aquifers (4 × 10⁻⁴–25 × 10⁻³ MJ) indicate that those of Mesohellenic Trough (Northwest Greece), Western Thessaloniki basin and Botsara flysch (Northwestern Greece) exhibit the best performance. Heat capacity was investigated in fourteen aquifers (throughout North and South Greece) and three abandoned mines of Central Greece. Results indicate that aquifers present higher average total heat energy values (up to ~6.05 × 10⁶ MWh_(th)), whereas abandoned mines present significantly higher average area heat energy contents (up to ~5.44 × 10⁶ MWh_(th)). Estimations indicate that the Sappes, Serres and Komotini aquifers could cover the space heating energy consumption of East Macedonia-Thrace region. Underground gas storage was investigated in eight aquifers, four gas fields and three evaporite sites. Results indicate that Prinos and South Kavala gas fields (North Greece) could cover the electricity needs of households in East Macedonia and Thrace regions. Hydrogen storage capacity of Corfu and Kefalonia islands is 53,200 MWh_(e). These values could cover the electricity needs of 6770 households in the Ionian islands. Petrographical and mineralogical studies of sandstone samples from the Mesohellenic Trough and Volos basalts (Central Greece) indicate that they could serve as potential sites for CO₂ storage.

The geothermal field of Akropotamos produces fluids at temperatures up to 90oC. The waters from wells AKR-1, AKR-3, AKR-4, AKR-5 and AKR-6 at 30 86oC and TDS of 3.1-30.7 g/l are classified as Na-Cl type. The water from well AKR-2 at 46oC with TDS of 2.15 g/l belongs to Na-HCO3Cl type. The cold and sub-thermal waters (16.4- 27oC) in the area are considered as fresh or low salinity waters (TDS: 0.31-4.34 g/l) of various mixed types. The Na-Cl geothermal waters can be divided into two categories due to two different hot aquifers: (a) Τhe first shallow aquifer contains high salinity waters (TDS: 27.4 30.7 g/l) at 30-48oC located within sands, sandstones and gravels. (b) Τhe second deeper reservoir composed of calcareous conglomerates and sandstones contains lower salinity waters (TDS: 3.1-5.08 g/l) at 83-90οC. The contribution of seawater to the chemical composition of the thermal waters in the shallow aquifer system seems to be important. With the aid of chemical geothermomometers applied to the geothermal water from well AKR-1, the deep temperature has been estimated to be >120oC. Significant quantities of CO2 are encountered in wells AKR-1 and AKR-3.

This paper describes the results of the preliminary surface geothermal exploration conducted by IGME in the basin of Katerini (Northern Greece). It mainly regards temperature measurements at the wellhead of 73 wells and in the interior of five boreholes, as well as sampling and chemical analyses from 18 selected sites. Based on the collected data, three sub-regions of geothermal interest can be distinguished, the most important of which is the area of Kato Agios Ioannis (to the south of the basin), with temperatures around 27oC at the depth of 340m. Nonetheless, the detailed geothermal investigation of this basin requires further systematic research as well as the drilling of at least one deep geothermal exploration borehole.

The Akropotamos area constitutes a new geothermal field located in the eastern coastal zone of the Strymonikos Gulf in Macedonia (Northern Greece). After a detailed and systematic reconnaissance study including water temperature measurements at the heads of the existing irrigation and water supply wells, 6 new geothermal wells were constructed. This geothermal drilling program was performed by the Institute of Geology and Mineral Exploration during October 2003 - February 2006. Temperature and fluid conductivity logs were carried out into these boreholes during their drilling and after their completion. Well AKR-1 has a depth of 275 m and produces thermal waters at a temperature of 83o C with artesian flow rate 150 m3 /h and large amounts of dissolved CO2. Well AKR- 2 of 410 m yields 25 m3 /h of waters at 46o C. Well AKR-3 was drilled down to 515 m and the temperature of 88.9o C was measured at 498 m. This well yields about 200 m3 /h CO2-rich geothermal fluids at a temperature of 90o C with artesian flow. Next to this borehole, well AKR-4 was drilled at 180 m penetrating a shallow aquifer with waters reaching 49.7o C. During pumping test with constant flow rate, this well yielded 40 m3 /h water of 48o C. Well AKR-5, 422 deep, was drilled in the western part of the study area close to the Strymon river’s mouth. The temperature of 27.8o C was recorded at 280 m into this borehole. The last well AKR-6 was drilled down to 545 m in the eastern part of the field. The temperature of 38o C was recorded at depth of 503 m. Pumping tests were performed in wells AKR-2 and AKR-4. This geothermal drilling project has resulted in the official characterization of the Akropotamos - Kavala area as a “proven low enthalpy geothermal field”.

The Strymon basin is one of the most important sedimentary basins in Northern Greece where significant geothermal fields are located. The SW part of the Strymon basin manifests geothermal interest. Available geophysical data (seismic, gravity, magnetic and electrical data) contributed to the identification of major faults that control the fluid-flow paths of the geothermal field and the estimation of depth to the metamorphic basement. The former is of great importance because the geothermal aquifer is expected to be at the contact of the basal conglomerate with the metamorphic basement. The highest thermal gradient values (10-15o C/100 m) were observed in the western part of the study area near the known geothermal field of Therma – Nigrita. Other important geothermal anomalies (>6o C/100 m) occur in the Patriki area, north of the village of Ivira and in the area between the villages of Patriki and Achinos. Geothermal interest manifests itself in the following areas: north of Mavrothalassa (>4o C/100 m), southwest of Ivira and east of Agios Dimitrios. It appears furthermore that the main thermal anomaly is associated with two NW-SE fault systems that affect the basement in the areas of Patriki and north of Achinos - Ivira correspondingly. These faults have been detected by the use of geophysical surveys. The presence of NE-SW faults extends the anomaly southwestwards.