| Abstract |
The Krsko field in eastern Slovenia is known for its thermal springs, appearing on its southern and western margins. The structure of the Krsko basin was delineated using several geophysical methods, as for instance gravimetry, deep resistivity sounding, well logging and reflection seismics. Geomagnetic survey revealed the probable existence of potential and highly speculative heat source beneath the Gorjanci and Zumberak mountains south of the Krsko basin. Temperature measurements in many shallow and in some deeper wells were done for geothermal gradient determination. Depths to carbonate reservoir, roughly determined with geophysics and proved by drilling in shallower places, reach about 1800 m in the central elongated part of the basin, and are much smaller along its southern margin. At the northern margin geophysics so far gave no signals of thermal water existence in depth. Thermal water occurrence is due to specific synclinal build up, with the impervious clastics overlying the aquiferous carbonates. Differences in thermal conductivities between Tertiary clastics filling the basin and Mesozoic carbonates are the cause of greater temperature gradients in Tertiary layers. Heat flow density is within average values over most of the field. On top of the carbonate aquifers temperatures attain more than 50 ?C in eastern part of the field. Thermal water with temperatures of up to 64 ?C and yield per well of up to 40 l/s is used for bathing, space and greenhouse heating. |