Mineral deposits affecting geothermal energy production – Insights, analytical approaches and implementation strategies

Unwanted mineral precipitation (scaling), clogging due to particle mobilization (plugging) and material alteration (corrosion) are common problems in hydrogeothermal facilities. Geochemistry and mineralogy contribute to the data-based evaluation of site-specific formation and mobilization conditions of individual solids in order to optimize energy yields (heat, electricity). “Scaling Forensics” is used to identify (un)favourable operating conditions and to develop installation-specific solutions based on a critical evaluation of the fluid-solid interaction and the analysis of unwanted mineral deposits in the fluid circuits. In addition to in-situ sampling and monitoring of the water, gases and solids involved, laboratory analyses and experiments as well as computer-aided numerical modelling are used, and indicative minerals, interfaces and textures are considered. An in-depth process understanding identifies countermeasures regarding (i) pumping conditions of the thermal water (bubble formation, pressure maintenance), (ii) suitable monitoring strategies (sensor technology, laboratory/field tests), (iii) addition of environmentally-friendly chemical inhibitors against mineral deposits based on systematic test series (active substances, products, dosages), (iv) adapted materials and substrates (coatings) and (v) geothermal concepts with alternative working fluids (e.g. CO2-based).