Exploration Techniques of Geothermal Energy (Ch. 4)

From the industrial point of view, geothermal energy is the internal heat of the Earth that is trapped in geological structures of the outer Earth's crust close enough to the surface to be economically exploited. These geological structures, which act as "heat mines", are the geothermal systems, and water is the natural working fluid by which heat is extracted from the rocks. This chapter describes the geochemical and geophysical techniques used in geothermal exploration to locate geothermal systems and to estimate temperature and chemical composition of the reservoir fluids before drilling. As the study of the oxygen and hydrogen isotope compositions of geothermal water and steam samples has probably contributed most to the understanding of the origins of these fluids and of the processes they undergo during their rise towards the Earth's surface, a concise description of the basics of stable isotope geochemistry applied to geothermal fluids is also included.