Institute of Geological Sciences

Geothermal Energy

Mineral scaling and corrosion in geothermal systems

We are investigating the processes that lead to reservoir clogging, mineral scaling and corrosion by incorporating chemical data from existing geothermal plants into our numerical simulations. The aims are to provide guidelines as how to avoid clogging and scaling, both in operating systems and as an aid in designing future systems.

Photographs of calcite scaling formed at various locations within the geothermal plant Kirchstockach, Germany: (a) at the pump, (b) along the casing, and (c) in the heat exchanger at the surface.

Profiles of mineral saturation indices (S.I.) through the production and injection wells at the operational Bad Blumau geothermal system (Styria, Austria). The left panels show profiles with the inhibition of Ca–Mg–Fe–carbonate precipitation. For comparison, the right panels show saturation profiles through the injection well without inhibition. Upper panels are carbonate minerals only, lower panels all other minerals (from Alt-Epping et al. 2013).

Equilibrium solubility curves (K) of silica minerals as a function of temperature for P–T conditions in the production well (190–170 °C) and surface heat exchanger (170–100 °C) of the hypothetical petrothermal system at Basel-1. Red line: silica concentration of the fluid (in molality, m) exiting the reservoir at 190 °C. Where the solubility curves and the log m(SiO2(aq)) of the production fluid intersect, saturation is attained and the saturation temperature can be determined. Note the high solubility and hence low saturation temperature (58 °C) of amorphous silica.

Predicted operation conditions to avoid silica scaling in the production well and surface installations of a model 5000 m deep petrothermal system based on the Basel-1 well (from Diamond and Alt-Epping, 2014).