• Energy Research

This data was collected to write an extensive review on organic compounds in geothermal fluids as part of the REFLECT (Redefining geothermal fluid properties at extreme conditions to optimize future geothermal energy extraction). The data is mainly focussed on geothermal sites were organic compound data was reported in the literature. It includes data from the literature (Feldbusch, 2016; Vetter, 2012; Brehme et al., 2019; Westphal et al., 2019; Sanjuan et al., 2016) as well as own data that was analysed at the GFZ German Research Centre for Geosciences in section 3.2 (Organic Geochemistry). It comprises 130 samples from 19 different sites including DOC, organic acid anion as well as main inorganic anion concentrations, well depths, and reservoir temperatures of various geothermal sites in Europe. Due to confidentiality agreements Site names are all given in ID’s which are fully explained in the publication “Organic compounds in geothermal fluids – a review” when available. Sample ID’s are also given if the samples, both from the literature or own samples were measured at GFZ German Research Centre for Geosciences. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 850626 (REFLECT).

This data was collected to write an extensive review on organic compounds in geothermal fluids as part of the REFLECT (Redefining geothermal fluid properties at extreme conditions to optimize future geothermal energy extraction). The data is mainly focussed on geothermal sites were organic compound data was reported in the literature. It includes data from the literature (Feldbusch, 2016; Vetter, 2012; Brehme et al., 2019; Westphal et al., 2019; Sanjuan et al., 2016) as well as own data that was analysed at the GFZ German Research Centre for Geosciences in section 3.2 (Organic Geochemistry). It comprises 130 samples from 19 different sites including DOC, organic acid anion as well as main inorganic anion concentrations, well depths, and reservoir temperatures of various geothermal sites in Europe. Due to confidentiality agreements Site names are all given in ID’s which are fully explained in the publication “Organic compounds in geothermal fluids – a review” when available. Sample ID’s are also given if the samples, both from the literature or own samples were measured at GFZ German Research Centre for Geosciences. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 850626 (REFLECT).

Abstract Leaching tests with synthetic brines (25 g/L NaCl) between 25 °C and 90 °C were performed under oxic and anoxic conditions over 7 days on two pyrite-bearing siliciclastic rocks from the Lower Jurassic Hettangian and Sinemurian stages in the North German Basin. The release mechanisms of the mobile elements Al, As, Ba, Ca, Cu, Fe, Mn, Ni, Si, and Pb were studied and explained by means of numerical simulations of the leaching tests. The study was performed in the context of aquifer thermal energy storage (ATES) to improve the understanding of water–rock interactions during heat storage. Results showed that release patterns of Ba, Ca, Cu, Fe, Ni, and Pb were predominantly controlled by the dissolution of pyrite under oxic conditions and iron hydroxides under anoxic conditions. The mobilizations of Al and Mn could be explained by a combination of desorption and the dissolution of hydroxides. Si was mainly released from amorphous silica. The mobilization of Ca was governed by pH-sensitive desorption and calcite dissolution in one of the samples. Arsenic was immobile in both studied rocks. In general, elemental release was augmented by the presence of oxygen and the subsequent dissolution of pyrite and reduction of pH, which should therefore be avoided in ATES systems.

Abstract Leaching tests with synthetic brines (25 g/L NaCl) between 25 °C and 90 °C were performed under oxic and anoxic conditions over 7 days on two pyrite-bearing siliciclastic rocks from the Lower Jurassic Hettangian and Sinemurian stages in the North German Basin. The release mechanisms of the mobile elements Al, As, Ba, Ca, Cu, Fe, Mn, Ni, Si, and Pb were studied and explained by means of numerical simulations of the leaching tests. The study was performed in the context of aquifer thermal energy storage (ATES) to improve the understanding of water–rock interactions during heat storage. Results showed that release patterns of Ba, Ca, Cu, Fe, Ni, and Pb were predominantly controlled by the dissolution of pyrite under oxic conditions and iron hydroxides under anoxic conditions. The mobilizations of Al and Mn could be explained by a combination of desorption and the dissolution of hydroxides. Si was mainly released from amorphous silica. The mobilization of Ca was governed by pH-sensitive desorption and calcite dissolution in one of the samples. Arsenic was immobile in both studied rocks. In general, elemental release was augmented by the presence of oxygen and the subsequent dissolution of pyrite and reduction of pH, which should therefore be avoided in ATES systems.

The efficiency and feasibility of geothermal utilisation depends strongly on the characteristics and behaviour of the fluids that transfer heat between the geosphere and the engineered components of a power plant. Chemical and physical processes such as precipitation, corrosion, or degassing are induced by pressure and temperature changes, with potentially serious consequences for power plant operation and project economics. The EU Horizon 2020-funded project REFLECT aims to avoid such problems by collecting high-quality chemical, physical, and microbiological data at extreme salinities, pressures or temperatures and improving the understanding of kinetic processes through laboratory experiments. These data are presented in a European geothermal fluid atlas and implemented in predictive models in order to provide recommendations on how to best operate geothermal systems for a sustainable future.

The efficiency and feasibility of geothermal utilisation depends strongly on the characteristics and behaviour of the fluids that transfer heat between the geosphere and the engineered components of a power plant. Chemical and physical processes such as precipitation, corrosion, or degassing are induced by pressure and temperature changes, with potentially serious consequences for power plant operation and project economics. The EU Horizon 2020-funded project REFLECT aims to avoid such problems by collecting high-quality chemical, physical, and microbiological data at extreme salinities, pressures or temperatures and improving the understanding of kinetic processes through laboratory experiments. These data are presented in a European geothermal fluid atlas and implemented in predictive models in order to provide recommendations on how to best operate geothermal systems for a sustainable future.

This dataset is part of a research collaboration between Energie und Wasser Potsdam (EWP) and the GFZ Helmholtz Centre for Geosciences. The main objective of this research collaboration was to evaluate the suitability of the subsurface in the Potsdam area for deep geothermal energy. EWP is currently constructing a geothermal power plant using the aquifer of the here exploited Jurassic sandstones. From December 2022 to May 2023, two deep wells were drilled in the center of the city Potsdam, Germany, targeting the Jurassic Aalenian Sandstone at depths between 983 and 1180 m below surface. Hydraulic tests were performed immediately after completion of each well. More than 15,000 m3 of formation water was produced. Geochemical analysis were performed on the produced formation water with the objective of characterizing the fluid properties in terms of geothermal usage, e.g. corrosion and scaling potential. The results of the analysis of physicochemical on-site monitoring and performed on-site tests, inorganics, organics, gas composition, heat capacity and naturally occurring radioactive materials are presented in this data publication.