| Title | First field experiments with fiber optics for geothermal potential assessment in Slovenia |
|---|---|
| Authors | Fiona Chapman |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | Active distributed temperature sensing (A-DTS), heat injection, fissured dolomite, intergranular gravel aquifer, marly aquitard |
| Abstract | Fibre-optic technology and distributed temperature sensing (FO-DTS) has been used globally for geothermal characterization. FO-DTS was paired with thermal response tests for the first time in Slovenia in February 2025. Previously, we relied on laboratory measurements to determine rock thermal properties and lately we integrated thermal response tests, but highly productive alluvial and karstic aquifers with strong groundwater flow often limit their applicability. With over 17,000 shallow geothermal systems across different lithologies, we are interested in detailed litho- and geothermal characterization. In spring 2025, we used equipment from GeoSphere and the Faculty of Civil and Geodetic Engineering to perform active distributed temperature sensing (ADTS) at three pilot sites, in collaboration with INRS. These tests used a composite FO and copper heating cable to evaluate thermal conductivity and temperature gradient at a resolution of 0.25 m, from which heat flow is calculated. All tests consisted of 3 day heating followed by 3-day thermal recovery. We compared stratified litho-geothermal properties of: i)a marly aquitard with a shallow alluvial aquifer in topmost part, both penetrated by a 100 m deep single U-tube geoprobe with FO cemented in the grout; ii)a fissured dolomite with few caverns, penetrated by 131 m deep abandoned artesian well, currently open and tested to about 90 m depth, and iii)a highly productive alluvial aquifer with average groundwater velocity of 10 m/day, penetrated by a 75 m deep monitoring well. In all cases values were compared with either lab or TRT results. |