Periodic Reporting for period 1 - EASYGO (Efficiency and Safety in Geothermal Operations)
Período documentado: 2020-11-01 hasta 2022-10-31
To mitigate climate change, the EU set a net-zero emission target by 2050. This long-term climate strategy plans the energy transition and energy decarbonization for the next decades. Currently, the EU relies on significant energy imports. The large price oscillations of natural gas recorded this past winter, followed by the shortage of gas supply as a result of the Ukraine war, have shown how vulnerable the whole energy system of Europe really is, and how dependent on the supply of primary resources. Geothermal energy will play a key role in the energy transition to renewables as part of mitigating climate change.
However, the operation of running geothermal fields is still a challenge. Most operating fields run into problems related to the interruption of the physical, chemical, and mechanical equilibrium at depth. These changes result in unexpected loss of fluids, mineral precipitation that clogs fluid pathways, corrosion that harms the infrastructure of power plants, mechanical reactions such as earthquakes or unwanted opening of cracks resulting in instability of the system. Therefore, there is a strong societal demand for a safe geothermal energy supply in the future along the question 'How to operate a geothermal system in the most efficient and safe manner?'.
However, the operation of running geothermal fields is still a challenge. Most operating fields run into problems related to the interruption of the physical, chemical, and mechanical equilibrium at depth. These changes result in unexpected loss of fluids, mineral precipitation that clogs fluid pathways, corrosion that harms the infrastructure of power plants, mechanical reactions such as earthquakes or unwanted opening of cracks resulting in instability of the system. Therefore, there is a strong societal demand for a safe geothermal energy supply in the future along the question 'How to operate a geothermal system in the most efficient and safe manner?'.
The overall research objectives of the EASYGO ITN program are to improve the efficiency and safety of geothermal operations by a detailed investigation of the subsurface and surface processes and their interdependencies. Efficiency and safety will ensure both cost-effective energy and equitable access to this resource with no adverse impacts on workers in the industry or on the wider society.
The individual research projects of the EASYGO research program cover the whole chain of geothermal operations. ESRs use onsite field measurements, laboratory experiments and novel simulation techniques. Major results have been achieved in the specific research topics.
Results of projects working on the heterogeneity of geothermal reservoirs highlight the importance of in-depth analysis of the fractures in the rock formation in terms of possible fluid flow. One study found a combination of geological models and geophysical data that is able to image 3D structures accurately while also calculating geophysical properties within the geological units.
To obtain data on heterogeneity a database of geochemical properties and seismic and electromagnetic data before and during geothermal operations at Dutch geothermal wells has been established. Based on the database potential injectivity problems for certain fields could be identified. Additionally, an acquisition setup has been developed for controlled-source electromagnetic monitoring with the aim to detect small resistivity changes in the reservoir.
To increase the efficiency of geothermal systems water in the subsurface is replaced with CO2. First laboratory experiments have been run to test reactions of CO2 with reservoir rock and see the performance of such a system. Also, adapted monitoring techniques for the real scale are developed. The joint use of seismics and GPR-techniques are identified as particularly promising. At the surface, if the fluids in the secondary cycle are replaced by eco-friendly mixtures or run through advanced cycle configurations such as the double pressure cycle, the power gain can range from 5% to 50%. A thermodynamic model was developed to reflect the interaction with the real geothermal brine.
Thermo-hydro-mechanical simulations have been run and showed that the injection temperature can significantly change the stress distribution around the wellbore, inducing notably tensile stresses that can impact significantly the near-borehole conductivity and injectivity. Also, the far-field cooling-induced stress perturbation can lead to fault reactivation around geothermal reservoirs. Combining physics and machine learning is used to predict these processes more efficiently and reliably.
The individual research projects of the EASYGO research program cover the whole chain of geothermal operations. ESRs use onsite field measurements, laboratory experiments and novel simulation techniques. Major results have been achieved in the specific research topics.
Results of projects working on the heterogeneity of geothermal reservoirs highlight the importance of in-depth analysis of the fractures in the rock formation in terms of possible fluid flow. One study found a combination of geological models and geophysical data that is able to image 3D structures accurately while also calculating geophysical properties within the geological units.
To obtain data on heterogeneity a database of geochemical properties and seismic and electromagnetic data before and during geothermal operations at Dutch geothermal wells has been established. Based on the database potential injectivity problems for certain fields could be identified. Additionally, an acquisition setup has been developed for controlled-source electromagnetic monitoring with the aim to detect small resistivity changes in the reservoir.
To increase the efficiency of geothermal systems water in the subsurface is replaced with CO2. First laboratory experiments have been run to test reactions of CO2 with reservoir rock and see the performance of such a system. Also, adapted monitoring techniques for the real scale are developed. The joint use of seismics and GPR-techniques are identified as particularly promising. At the surface, if the fluids in the secondary cycle are replaced by eco-friendly mixtures or run through advanced cycle configurations such as the double pressure cycle, the power gain can range from 5% to 50%. A thermodynamic model was developed to reflect the interaction with the real geothermal brine.
Thermo-hydro-mechanical simulations have been run and showed that the injection temperature can significantly change the stress distribution around the wellbore, inducing notably tensile stresses that can impact significantly the near-borehole conductivity and injectivity. Also, the far-field cooling-induced stress perturbation can lead to fault reactivation around geothermal reservoirs. Combining physics and machine learning is used to predict these processes more efficiently and reliably.
EASYGO graduates will be the first generation of multidisciplinary experts with a standardized education in geothermal operations. Their research results have a direct impact on society and economy. An efficient and safe supply in the future is identified as a strong societal demand. Three different approaches are used to obtain data and knowledge: field measurements, laboratory experiments, and numerical simulation.
“How do we run geothermal systems efficiently?”
A database has been developed based on field data on hydrogeochemical properties of geothermal reservoirs in the Netherlands. It systemizes the current knowledge, makes it openly accessible, and increases the possibilities of using geothermal energy in the Netherlands for upcoming projects, e.g. the Delft Adwarmte Project. Additionally, high-resolution outcrop models were obtained using unmanned aerial vehicle-based digital photogrammetric data. The data are used to build models that allow the identification of discontinuities and related subsurface fluid flow. Also, laboratory experiments can bring relevant information. A novel laboratory-scale pilot test of CO2-based geothermal energy investigates the permeability evolution and chemical performance of a CO2-based geothermal reservoir under elevated pressure and temperature conditions. Modeling these data with a focus on thermo-hydro-mechanical processes shows that lower injection temperatures can induce thermal fractures that can impact the near-borehole conductivity and injectivity. An integrating numerical simulation approach, which combines geophysical data and geo-models allows updating the model's geometry while also calculating its geophysical properties within the lithological units. At the surface, geothermal power plants can be optimized by using a different secondary fluid for heat extraction. Steady-state cycle computations and optimization algorithms have been used to find zeotropic mixtures as optimal working fluids for binary power plants due to their non-isothermal phase change. Also, minimizing the average temperature difference between the geofluid and cycle working fluid is a key object for the design of the heat introduction system, in order to achieve high overall conversion efficiency.
“How do we run geothermal systems safely?”
Advanced and integrated monitoring concepts have been developed to observe and measure processes in the subsurface prior to and during decades of operation. A controlled-source electromagnetic monitoring survey has been tested to detect small resistivity changes as expected for a deep low-enthalpy reservoir. Small resistivity changes are caused by the replacement of the original hot water in the underground with cold water. Seismic events associated with the injection and extraction of water in geothermal reservoirs have been studied using long-term seismic monitoring. To understand the reason and source of seismic events fracture patterns in the subsurface have to be studied in detail. Seismic monitoring combined with GPR measurements have been proven to be optimal for monitoring, especially CO2 based systems. Existing databases have been used to study cooling induced stress changes on the laboratory, medium and full reservoir scale. Monte-Carlo simulations and machine learning is used to provide real-time analysis of data during operation. All these advancements will ensure safe operations with no adverse impacts on workers in the industry or on the wider society.
“How do we run geothermal systems efficiently?”
A database has been developed based on field data on hydrogeochemical properties of geothermal reservoirs in the Netherlands. It systemizes the current knowledge, makes it openly accessible, and increases the possibilities of using geothermal energy in the Netherlands for upcoming projects, e.g. the Delft Adwarmte Project. Additionally, high-resolution outcrop models were obtained using unmanned aerial vehicle-based digital photogrammetric data. The data are used to build models that allow the identification of discontinuities and related subsurface fluid flow. Also, laboratory experiments can bring relevant information. A novel laboratory-scale pilot test of CO2-based geothermal energy investigates the permeability evolution and chemical performance of a CO2-based geothermal reservoir under elevated pressure and temperature conditions. Modeling these data with a focus on thermo-hydro-mechanical processes shows that lower injection temperatures can induce thermal fractures that can impact the near-borehole conductivity and injectivity. An integrating numerical simulation approach, which combines geophysical data and geo-models allows updating the model's geometry while also calculating its geophysical properties within the lithological units. At the surface, geothermal power plants can be optimized by using a different secondary fluid for heat extraction. Steady-state cycle computations and optimization algorithms have been used to find zeotropic mixtures as optimal working fluids for binary power plants due to their non-isothermal phase change. Also, minimizing the average temperature difference between the geofluid and cycle working fluid is a key object for the design of the heat introduction system, in order to achieve high overall conversion efficiency.
“How do we run geothermal systems safely?”
Advanced and integrated monitoring concepts have been developed to observe and measure processes in the subsurface prior to and during decades of operation. A controlled-source electromagnetic monitoring survey has been tested to detect small resistivity changes as expected for a deep low-enthalpy reservoir. Small resistivity changes are caused by the replacement of the original hot water in the underground with cold water. Seismic events associated with the injection and extraction of water in geothermal reservoirs have been studied using long-term seismic monitoring. To understand the reason and source of seismic events fracture patterns in the subsurface have to be studied in detail. Seismic monitoring combined with GPR measurements have been proven to be optimal for monitoring, especially CO2 based systems. Existing databases have been used to study cooling induced stress changes on the laboratory, medium and full reservoir scale. Monte-Carlo simulations and machine learning is used to provide real-time analysis of data during operation. All these advancements will ensure safe operations with no adverse impacts on workers in the industry or on the wider society.