Inhaltsbereich
High Temperature Instruments for supercritical geothermal reservoir characterization and exploitation
HITI
The European HITI project aims to provide geophysical and geochemical sensors and methods to evaluate deep geothermal wells up to supercritical conditions (T>380°C). Supercritical geothermal wells are presently non-conventional but may provide a very efficient way to produce electricity from a clean, renewable source.
GFZ Part in Workpackage 4: Production integrity monitoring
Within HITI, new surface and downhole tools and approaches for deep high-temperature boreholes are developed, built, and tested in the field. The new set of tools and methods has been chosen to provide a basic set of data needed to describe either the supercritical reservoir structure and dynamics (measurement of temperature, pressure, natural gamma radiation, electrical resistivity, reservoir storativity, and acoustic imaging of the borehole wall), and the evolution of the casing and cement integrity during production (acoustic imaging). The new tools will be tested in-situ in existing Icelandic wells, including the IDDP (“Iceland Deep Drilling Project”) hole.
Within workpackage 4 “Production Integrity Monitoring”, GFZ contributes its expertise in fiber-optic temperature monitoring, which is further developed for the specific demands in high-temperature geothermal wells. The current system was deployed in 4.2 km depth at temperatures of 146 °C at the In-situ Geothermal Lab in Groß-Schönebeck (Henninges et al., 2005). Within HITI, a DTS sensor cable will be tested during a field experiment in a high-enthalpy geothermal reservoir in Iceland.
Pressure-enthalpy diagram
© Fournier (1999)- Pressure-enthalpy diagram for pure H2O with selected isotherms. The conditions under which steam and water coexist is shown by the shaded area, bounded by the boiling point curve to the left and the dew point curve to the right. The arrows show various different possible cooling paths (Fournier, 1999).
The pressure-enthalpy diagram for pure water (Figure 1) from Fournier (1999) provides a summary of how a supercritical geothermal system might be managed to produce electricity. For more explanations see: European-Projekt HITI