Dissolved Helium as Indicator for Geothermal Water Prospecting

Abstract

The essence of this method is the study of helium in the accessible part of the lithosphere. The present paper is a summary of data obtained on helium dissolved in cold and geothermal groundwaters of Southern Bulgaria. More than 1000 samples from different water sources have been studied. Data were obtained on an analytical device "INGEM ñ 1". Helium distribution in the geothermal waters in two regions of Southern Bulgaria is viewed in more detail. The content of helium in groundwater varies widely for Bulgaria ñ from 0.5 Pa for the cold ground waters to more than 1 000 Pa for the geothermal waters. Also presented is the spatial distribution of helium and outlines the areas of maximal concentrations. This "picture" provides information about the existence and approximate location of tectonic faults and geothermal waters. Concentration of helium in waters commonly increases with increasing water temperature. A comparison between the helium and heat flow distribution in Southern Bulgaria is made. The results show that helium content in the waters can be a reliable and independent indicator for thermal water prospecting.