The GNG team from GNS Science’s Experimental Geochemistry Laboratory completed a study on the solubility of anhydrite in water at supercritical conditions from 380°C to 625°C and 220 bar to 270 bar. The recently published journal paper is dedicated to the memory of Prof. Terry M. Seward (1940-2022).
The results cover the approximate range of temperature and pressure expected to be found in deep geothermal systems where supercritical conditions could be expected. Anhydrite solubility has not been previously well-defined in this region and a new empirical equation was calibrated. This equation will be necessary for surface and subsurface engineering in supercritical geothermal projects.
The experiments were performed using the new flow-through reactor, installed as part of this project, capable of reaching supercritical conditions. The utilization of the unique laboratory facility has pushed the boundaries of experimental capabilities in supercritical research. In addition to thermodynamic studies of mineral stability (e.g. quartz, anhydrite), the facility has been the first in the world to simulate geothermal brine, both with and without added CO2, into host rocks under supercritical conditions.
GNS Science’s experimental geochemistry capabilities are being expanded in 2024 with the acquisition of the new continuous hydrothermal fluid apparatus that will enable testing up to 600°C and 500 bar. The data generated are crucial for the successful development of supercritical geothermal projects, as they are fundamental to the modelling of subsurface scaling and mineralization.