The efficiency of geothermal use depends on the behaviour of the fluids that transfer heat between the geosphere and the engineered components of a power plant. The physical and chemical properties of the fluids are often poorly defined because in situ sampling and measurements under extreme conditions are difficult and lead to large uncertainties in model predictions. Extreme conditions are those with fluid temperatures > 100°C up to critical conditions and / or salinity > 35 g/l (higher than seawater).
To extend thermodynamic databases, this special issue focuses on recent studies of experimental or in situ investigations of the chemical, physical, and microbial properties of fluids and the implementation of these results.
However, there are many engineering and chemical problems caused by geothermal fluid. In view of these outstanding fluid-rock interactions in hydrothermal systems, this special issue seeks to redefine the properties of geothermal fluids under extreme conditions to understand the current function of geothermal energy for sustainable development.
The main topics of interest are:
• Research to extend thermodynamic databases (solubility, activity, reaction kinetics) to higher temperatures and higher salinities through laboratory experiments and modelling approaches
• Research to determine the extent and location of the degassing front of geothermal fluids during production (field, laboratory, and modelling approaches)
• Research to characterise the types of organic matter and microorganisms in various geothermal fluids and their effect on scaling and biofilm formation through laboratory studies
• Studies on heat capacity, density, electrical and thermal conductivity, sonic velocity, and viscosity at different p, T, X through laboratory experiments and modelling approaches
• Development of a sampling technique suitable for collecting fluids in hot and superheated systems
• Application in reactive transport modelling at high temperatures and salinities
• Database and platforms to collect information on geothermal fluid properties across Europe, together with their geological environment
• Also, results from the Horizon 2020 REFLECT project will be compiled in this special issue.