The main objective of the work package 2 of the REFLECT project is to characterise relevant fluid properties and their reactions for saline fluids (type C). One of the specific goals was to collect fluid samples from several saline fluids from geothermal sites across Europe, determine their properties, and thus contribute to the Fluid Atlas (WP3). Additionally, the REFLECT team will compare those field data with data from lab experiments performed at near natural conditions. Samples of type C fluids were taken from several sites in Germany, Austria, Belgium and the Netherlands. The samples were analysed for major and minor ions, dissolved gases and isotopes. One sample of thermal water was taken from the production well at Balmatt, Belgium on May 17th 2021 and sent to Hydroisotop for analysis of main cations and anions and heavy metals. It can be seen that the nitrate content is remarkably high. However, all meaurements had to be conducted from the same sample bottle, which had been acidified, presumably ... : Project summary: The efficiency of geothermal utilisation largely depends on the behaviour of fluids that transfer heat between the geosphere and the engineered components of a power plant. The Horizon 2020 funded project REFLECT aims to avoid problems related to fluid chemistry rather than treat them. Fluid physical and chemical properties are often poorly defined, as in situ sampling and measurements at extreme conditions have proved difficult to date. Therefore, large uncertainties in current model predictions prevail, which are being tackled in REFLECT by collecting new, high-quality data in critical areas. The data is being implemented in a European geothermal fluid atlas and in predictive models to allow recommendations on how to best operate geothermal sites sustainably and to enhance geothermal technology development. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 850626. Project website: ...