Periodic Reporting for period 2 - REFLECT (Redefining geothermal fluid properties at extreme conditions to optimize future geothermal energy extraction)
Reporting period: 2021-07-01 to 2023-09-30
The one problem plaguing almost all deep geothermal operations in the world is related to the chemistry of the geothermal fluids. In order to maximise both the operational efficiency and economic returns of geothermal power plants, it is vital that the geothermal systems work well for long periods without requiring significant maintenance. Key to this is preventing deleterious physical and chemical reactions such as degassing and mineral precipitation. An accurate prediction of those reactions is challenging, due to poorly defined fluid properties, largely as a consequence of the difficulty in determining these properties at in-situ geothermal conditions (i.e. extremely hot or saline fluids, high pressure). REFLECT addressed these challenges and redefined fluid properties through the acquisition of key new thermodynamic and kinetic reaction data. The data are implemented in predictive models to determine fluid reactions at extreme conditions, and into a comprehensive European Fluid Atlas. They will facilitate optimisation of future geothermal energy extraction: all results within REFLECT have been developed with a view towards significantly expanding maintenance intervals for geothermal installations and thus reducing operational costs, increasing well performance and improving plant layout. The ultimate goal of REFLECT is thus to lead to an increased number of geothermal projects.
Geothermal fluids have been sampled at 10 high-temperature and high-salinity geothermal sites. Samples have been analysed regarding their inorganic chemical properties, organic compounds and microbiology. In order to extend databases of solubility, activity, and reaction kinetics, REFLECT partners have established and verified three different high-temperature experimental setups, including traditional photometric methods, in situ Raman and conductimetric methods. These measurements provide new thermodynamic and kinetic data concerning the dissolution and precipitation of silica.
The degassing of CO2 and N2 saturated water has been studied optically using a visual cell and a high-speed camera at elevated temperatures (up to 150 °C) and pressures (up to 200 bar). These experiments delivered gas dissolution constants which are necessary to determine the extent and location of the degasification front of geothermal fluids. Additionally, degassing of CO2 has also been studied inside porous media by performing a series of coreflood experiments.
An extensive review of existing information on organic matter and microorganisms in geothermal fluids has been conducted. Organic compounds and microbiological diversity have been assessed for 8 geothermal sites and drastic differences have been observed between injection and production wells, which evidences that microbial growth can happen within the fluids during production.
Experimentally, electrical conductivities of carbonate solutions at different concentrations have been measured up to 450°C to determine limiting conductivities and association constants. Numerically, a new thermodynamic model for the H-Li-Na-K-Ca-Mg-Cl-H2O chemical system has been developed, from dilute solutions up to salts solubility, and for temperatures up to 250°C.
A high-temperature downhole sampler was designed and built. With its sealing mechanism, the sampler has potential to take a geothermal fluid sample, e.g. liquid, steam or two-phase geothermal fluid, at the required depth in a high-temperature to ultra-high temperature geothermal wells.
REFLECT researchers have improved numerical models in order to predict the geochemical processes occurring within the wellbores during the production of geothermal fluids and optimize the fluid flow behaviour in the geothermal loop. A new numerical model coupling hydraulic and chemical processes was developed and applied to different case studies. Furthermore, a framework was developed to support operational decisions to minimize scaling in geothermal plants under uncertainties. This framework consists of three elements, (a) a modelling workflow, (b) an uncertainty quantification model and (c) an optimization tool.
The European Fluid Atlas is an on-line query and visualization toolset for the geothermal well-fluid-rock-reservoir dataset compiled by the REFLECT project Geothermal fluid data from 21 European countries have been collected. The European Fluid Atlas (EFA) is available online in open-access.
The degassing of CO2 and N2 saturated water has been studied optically using a visual cell and a high-speed camera at elevated temperatures (up to 150 °C) and pressures (up to 200 bar). These experiments delivered gas dissolution constants which are necessary to determine the extent and location of the degasification front of geothermal fluids. Additionally, degassing of CO2 has also been studied inside porous media by performing a series of coreflood experiments.
An extensive review of existing information on organic matter and microorganisms in geothermal fluids has been conducted. Organic compounds and microbiological diversity have been assessed for 8 geothermal sites and drastic differences have been observed between injection and production wells, which evidences that microbial growth can happen within the fluids during production.
Experimentally, electrical conductivities of carbonate solutions at different concentrations have been measured up to 450°C to determine limiting conductivities and association constants. Numerically, a new thermodynamic model for the H-Li-Na-K-Ca-Mg-Cl-H2O chemical system has been developed, from dilute solutions up to salts solubility, and for temperatures up to 250°C.
A high-temperature downhole sampler was designed and built. With its sealing mechanism, the sampler has potential to take a geothermal fluid sample, e.g. liquid, steam or two-phase geothermal fluid, at the required depth in a high-temperature to ultra-high temperature geothermal wells.
REFLECT researchers have improved numerical models in order to predict the geochemical processes occurring within the wellbores during the production of geothermal fluids and optimize the fluid flow behaviour in the geothermal loop. A new numerical model coupling hydraulic and chemical processes was developed and applied to different case studies. Furthermore, a framework was developed to support operational decisions to minimize scaling in geothermal plants under uncertainties. This framework consists of three elements, (a) a modelling workflow, (b) an uncertainty quantification model and (c) an optimization tool.
The European Fluid Atlas is an on-line query and visualization toolset for the geothermal well-fluid-rock-reservoir dataset compiled by the REFLECT project Geothermal fluid data from 21 European countries have been collected. The European Fluid Atlas (EFA) is available online in open-access.
REFLECT extends the formerly limited experimental data on the thermodynamic and thermophysical properties of high temperature brines for various salt contents. Using the knowledge on fluid properties generated in REFLECT, the range of application for geothermal energy conversion can be significantly expanded to hotter and more saline conditions.
New technologies to anticipate fluid reactions and properties that are encountered in superhot geothermal environments are essential. REFLECT developed a Prototype for a downhole sampling technique, which will expand the range of condition-dependent chemical data available for interpretation of geothermal fluid behaviour. This innovation will enable fluid sampling from hot and super-hot wells.
Setting up a European Fluid Atlas that maps variations in fluid properties with geography, geology, and depth will facilitate the selection of new potential geothermal locations. To enable effective design and layout of new geothermal power plants it is critical that the geochemical fluid properties, as well as potential degassing and microbial risks, can be anticipated before work on the infrastructure begins.
A workflow has been established for operational decision support under uncertainties using a robust optimization algorithm to determine the optimum production decisions. As a result, the best performance protocols of geothermal power plants can be obtained.
Finally, REFLECT researchers have developed an approach to determine risk maps for the assessment of scaling risks where no operational experiences exist yet. Those risk maps can advise future operators on how to best design and operate their geothermal system to prevent scaling. Again, the European Fluid Atlas provides a unique opportunity to access and regional fluid data and to use that data for regional scaling risk assessment.
Therefore, REFLECT will have a significant impact on the development of geothermal systems and on the overall electricity supply generated from renewable energy sources through:
• Significantly increased technology performance and reduced maintenance costs leading to increased electricity output and faster amortization of the power plant due to reduced downtime and maintenance during operation,
• Reduced life-cycle environmental impact (reducing the release of non-condensable gases to the atmosphere by determining gas dissolution kinetics; minimizing the addition of chemicals (inhibitors) to the geothermal fluid for the prevention of scaling and corrosion)
• Facilitated exploitation of high-temperature geothermal resources (by adapting down-hole sampling technologies to higher temperatures, the correct characterization of very hot geothermal fluids can be achieved)
REFLECT’s main impact will thus be an improved EU energy security: By encouraging an increase of the share of geothermal energy within the European energy market, REFLECT can help to reduce the consumption of fossil fuels and reach the aims of the EU Green Deal.
New technologies to anticipate fluid reactions and properties that are encountered in superhot geothermal environments are essential. REFLECT developed a Prototype for a downhole sampling technique, which will expand the range of condition-dependent chemical data available for interpretation of geothermal fluid behaviour. This innovation will enable fluid sampling from hot and super-hot wells.
Setting up a European Fluid Atlas that maps variations in fluid properties with geography, geology, and depth will facilitate the selection of new potential geothermal locations. To enable effective design and layout of new geothermal power plants it is critical that the geochemical fluid properties, as well as potential degassing and microbial risks, can be anticipated before work on the infrastructure begins.
A workflow has been established for operational decision support under uncertainties using a robust optimization algorithm to determine the optimum production decisions. As a result, the best performance protocols of geothermal power plants can be obtained.
Finally, REFLECT researchers have developed an approach to determine risk maps for the assessment of scaling risks where no operational experiences exist yet. Those risk maps can advise future operators on how to best design and operate their geothermal system to prevent scaling. Again, the European Fluid Atlas provides a unique opportunity to access and regional fluid data and to use that data for regional scaling risk assessment.
Therefore, REFLECT will have a significant impact on the development of geothermal systems and on the overall electricity supply generated from renewable energy sources through:
• Significantly increased technology performance and reduced maintenance costs leading to increased electricity output and faster amortization of the power plant due to reduced downtime and maintenance during operation,
• Reduced life-cycle environmental impact (reducing the release of non-condensable gases to the atmosphere by determining gas dissolution kinetics; minimizing the addition of chemicals (inhibitors) to the geothermal fluid for the prevention of scaling and corrosion)
• Facilitated exploitation of high-temperature geothermal resources (by adapting down-hole sampling technologies to higher temperatures, the correct characterization of very hot geothermal fluids can be achieved)
REFLECT’s main impact will thus be an improved EU energy security: By encouraging an increase of the share of geothermal energy within the European energy market, REFLECT can help to reduce the consumption of fossil fuels and reach the aims of the EU Green Deal.