Geothermal fluids have been sampled at 10 high-temperature and high-salinity geothermal sites. Samples have been analysed regarding their inorganic chemical properties, organic compounds and microbiology. In order to extend databases of solubility, activity, and reaction kinetics, REFLECT partners have established and verified three different high-temperature experimental setups, including traditional photometric methods, in situ Raman and conductimetric methods. These measurements provide new thermodynamic and kinetic data concerning the dissolution and precipitation of silica.
The degassing of CO2 and N2 saturated water has been studied optically using a visual cell and a high-speed camera at elevated temperatures (up to 150 °C) and pressures (up to 200 bar). These experiments delivered gas dissolution constants which are necessary to determine the extent and location of the degasification front of geothermal fluids. Additionally, degassing of CO2 has also been studied inside porous media by performing a series of coreflood experiments.
An extensive review of existing information on organic matter and microorganisms in geothermal fluids has been conducted. Organic compounds and microbiological diversity have been assessed for 8 geothermal sites and drastic differences have been observed between injection and production wells, which evidences that microbial growth can happen within the fluids during production.
Experimentally, electrical conductivities of carbonate solutions at different concentrations have been measured up to 450°C to determine limiting conductivities and association constants. Numerically, a new thermodynamic model for the H-Li-Na-K-Ca-Mg-Cl-H2O chemical system has been developed, from dilute solutions up to salts solubility, and for temperatures up to 250°C.
A high-temperature downhole sampler was designed and built. With its sealing mechanism, the sampler has potential to take a geothermal fluid sample, e.g. liquid, steam or two-phase geothermal fluid, at the required depth in a high-temperature to ultra-high temperature geothermal wells.
REFLECT researchers have improved numerical models in order to predict the geochemical processes occurring within the wellbores during the production of geothermal fluids and optimize the fluid flow behaviour in the geothermal loop. A new numerical model coupling hydraulic and chemical processes was developed and applied to different case studies. Furthermore, a framework was developed to support operational decisions to minimize scaling in geothermal plants under uncertainties. This framework consists of three elements, (a) a modelling workflow, (b) an uncertainty quantification model and (c) an optimization tool.
The European Fluid Atlas is an on-line query and visualization toolset for the geothermal well-fluid-rock-reservoir dataset compiled by the REFLECT project Geothermal fluid data from 21 European countries have been collected. The European Fluid Atlas (EFA) is available online in open-access.
