Thermal Water Cycle
Hydrochemistry of geothermal systems
The chemistry of geothermal fluids is largely controlled by temperature-dependent water-rock interactions and fluid origin. These processes leave a fingerprint on the chemical and isotopic composition. With appropriate analyses, exploration-relevant questions (reservoir temperature, sustainability of the resource, etc.) can be answered. Special focus of our research is on the development of new methods for reservoir temperature determination using geochemical modeling and machine learning. Another focus is on the further development of classical geochemical exploration.
Surface heat extraction and depressurization during production alter the physical, hydrochemical, and thermodynamic parameters of geothermal water, disrupting the chemical system. Consequential reactions may include mineral precipitation (scaling). Current work is concerned with the numerical quantification of mineral precipitation to determine scaling potential and for design calculations of scaling avoidance measures. The BrineMine project has succeeded in developing a method for the targeted element-specific precipitation of SiO2. In this way, silica scaling can be effectively prevented, for example, in the run-up to mineral extraction.
- Dissertation Lars Yström: New methods in geothermometry
- Dissertation Valentin Goldberg: Selective extraction of dissolved components from geothermal fluids
Ystroem, L. H.; Nitschke, F.; Held, S.; Kohl, T. 2020. A multicomponent geothermometer for high-temperature basalt settings. Geothermal Energy, 8 (2).
Held, S.; Schill, E.; Schneider, J.; Nitschke, F.; Morata, D.; Neumann, T.; Kohl, T. 2018. Geochemical characterization of the geothermal system at Villarrica volcano, Southern Chile; Part I: Impacts of lithology on the geothermal reservoir. Geothermics, 74, 226–239.
Nitschke, F.; Held, S.; Neumann, T.; Kohl, T. 2018. Geochemical characterization of the Villarrica geothermal system, Southern Chile, Part II: Site-specific re-evaluation of SiO₂ and Na-K solute geothermometers. Geothermics, 74, 217–225.
Nitschke, F.; Held, S.; Himmelsbach, T.; Kohl, T. 2017. THC simulation of halite scaling in deep geothermal single well production. Geothermics, 65, 234–243.
Nitschke, F.; Scheiber, J.; Kramar, U.; Neumann, T. 2014. Formation of alternating layered Ba-Sr-sulfate and Pb-sulfide scaling in the geothermal plant of Soultz-sous-Forêts. Journal of Mineralogy and Geochemistry, 191 (2), 145–156.
Flow paths and reservoir hydraulics
The performance of a reservoir is largely determined by its geometry, the spatial distribution of flow paths and their hydraulic properties. In geothermal reservoirs, fluorescent dyes are often injected and their recovery is measured to characterize the hydraulic these parameters. In collaboration with Prof. Schimmel's group at the Institute of Nanotechnology (INT), we are developing "Smart Nanoparticle Tracers with Reporting Function". In addition to recovery as a concentration-over-time measurement, our approach also aim for detecting other reservoir parameters, such as temperature along the flow path.
Fluid flow in pre-existent and sheared fractures in a virtually dense rock matrix is characteristic for Enhanced Geothermal Systems (EGS). Geothermal-typical hydraulic boundary conditions together with the complex fracture geometries can cause turbulence-like flow behavior. In order to investigate the still unsolved central issues regarding hydraulics, transport and their impact on fluid chemistry in this context, we have established the DFG-funded F4aT (Forced Fracture Fluid Flow and Transport) hydraulic laboratory. By means of a 3D scanner, 3D printer and hydraulic test set-up, turbulent flow on rough fractures can be represented experimentally. The results are used to improve process understanding and to calibrate and parameterize numerical models.
- Dissertation Laura Spitzmüller: Development and application of Smar Nanoparticle Tracers
- F4aT – Laboratory for experimental investigation of fracture hydraulics
Egert, R.; Nitschke F.; Gholami Korzani, M.; Kohl, T. 2021. Stochastic 3D Navier-Stokes Flow in Self-Affine Fracture Geometries Controlled by Anisotropy and Channeling. Geophysical Research Letters. 2021.
Rudolph, B.; Berson, J.; Held, S.; Nitschke, F.; Wenzel, F.; Kohl T.; Schimmel, T. 2020. Thermo-reporting nanoparticles for accurate sensing of geothermal reservoir conditions. Scientific Reports 11422.
Marchand, S.; Mersch, O.; Selzer, M.; Nitschke, F.; Schoenball, M.; Schmittbuhl, J.; Nestler, B.; Kohl, T. 2020. A Stochastic Study of Flow Anisotropy and Channeling in Open Rough Fractures. Rock mechanics and rock engineering, 53, 233–249.