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High-temperature aquifer thermal energy storage (HT-ATES) systems can help in balancing energy demand and supply for better use of infrastructures and resources. The aim of these systems is to store high amounts of heat to be reused later. HT-ATES requires addressing problems such as variations of the properties of the aquifer, thermal losses and t...
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... the studied system, the energy recovery factor grows about twice as fast in the back injection as in the injection (Fig. 11). The aquifer is storing more and more heat with (2022) 10:23 time. The energy recovery factor increases to 0.89 asymptotically for a decade of operation. This value is in agreement with the relation between R a -η proposed by Gutierrez- Neri et al. ...
Context 2
... the studied system, the energy recovery factor grows about twice as fast in the back injection as in the injection (Fig. 11). The aquifer is storing more and more heat with (2022) 10:23 time. The energy recovery factor increases to 0.89 asymptotically for a decade of operation. This value is in agreement with the relation between R a -η proposed by Gutierrez- Neri et al. ...
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Citations
... The substantial costs linked to BTES construction emphasize the need for numerical simulations to ensure both economic viability and thermodynamic efficiency. Thermal injection in the BTES projects involves a range of temperature variations in the surrounding soil formations, which may affect the stability of the boreholes and the operational life of the projects [11][12][13]. As is shown in Fig. 1, a BTES project tends to store heat in low permeable layers that are rich in clay soils to minimize heat loss. ...
... Nevertheless, local mass imbalances between the injection and production areas remain and are investigated in this study. Previous research mainly focused on (i) uplift caused by poroelasticity for a single injection period (Birdsell and Saar 2020), (ii) the influence of poro-and thermoelasticity on the storage efficiency (Jin et al. 2020(Jin et al. , 2022, and (iii) the sensitivity of hydraulic parameters (e.g., the reservoir permeability) on the resulting uplift (Vidal et al. 2022). ...
... 0.6 mm for all reservoir depths) is attenuated towards the ground surface as the path length increases. This finding aligns with earlier results by Birdsell and Saar (2020), but contradicts the results of Vidal et al. (2022), who simulated counterintuitively increasing vertical displacements towards the ground surface due to their choice of boundary conditions. This is particularly evident in the employment of zero vertical displacement boundary conditions at the lateral boundaries of the model by Vidal et al. (2022) in addition to rollers only [as used in this study and also, for instance, in Birdsell and Saar (2020)]. ...
... This finding aligns with earlier results by Birdsell and Saar (2020), but contradicts the results of Vidal et al. (2022), who simulated counterintuitively increasing vertical displacements towards the ground surface due to their choice of boundary conditions. This is particularly evident in the employment of zero vertical displacement boundary conditions at the lateral boundaries of the model by Vidal et al. (2022) in addition to rollers only [as used in this study and also, for instance, in Birdsell and Saar (2020)]. In addition, the limited lateral extent of the model (200 m in contrast to approximately 6 km in this study) may influence the results. ...
High-temperature aquifer thermal energy storage (HT-ATES) systems are designed for seasonal storage of large amounts of thermal energy to meet the demand of industrial processes or district heating systems at high temperatures (> 100 °C). The resulting high injection temperatures or pressures induce thermo- and poroelastic stress changes around the injection well. This study estimates the impact of stress changes in the reservoir on ground surface deformation and evaluates the corresponding risk. Using a simplified coupled thermo-hydraulic-mechanical (THM) model of the planned DeepStor demonstrator in the depleted Leopoldshafen oil field (Upper Rhine Graben, Germany), we show that reservoir heating is associated with stress changes of up to 6 MPa, which can cause vertical displacements at reservoir depth in the order of 10 –3 m in the immediate vicinity of the hot injection well. Both the stress changes and the resulting displacements in the reservoir are dominated by thermoelasticity, which is responsible for up to 90% of the latter. Uplift at the surface, on the contrary, is primarily controlled by poroelasticity with by two orders of magnitude attenuated displacements of << 10 –3 m. Our calculations further show that the reservoir depth, elastic modulus, and injection/production rates are the dominant controlling parameters for the uplift, showing variations of up to two order of magnitudes between shallower reservoirs with low elastic moduli and deeper and more competent reservoirs. In addition, our findings demonstrate that the cyclic operation of HT-ATES systems reduces the potential for uplift compared to the continuous injection and production of conventional geothermal doublets, hydrocarbon production, or CO 2 storage. Consequently, at realistic production and injection rates and targeting reservoirs at depths of at least several hundred meters, the risk of ground surface movement associated with HT-ATES operations in depleted oil fields in, e.g., the Upper Rhine Graben is negligible.
... The injection of heat into the subsurface will in increase the thermal stress and might also cause uplift due to thermal expansion. Vidal et al. (2022) performed coupled thermo-hydrologic-mechanical (THM) modeling of the HEATSTORE Bern pilot site to evaluate the potential for surface uplift. The proposed HT-ATES site would store heat in a series of confined sandstone aquifers between 200 to 500 m in depth. ...
One of the critical challenges of the green energy transition is resolving the mismatch between energy generation provided by intermittent renewable energy sources such as solar and wind and the demand for energy. There is a need for large amounts of energy storage over a range of time scales (diurnal to seasonal) to better balance energy supply and demand. Subsurface geologic reservoirs provide the potential for storage of hot water that can be retrieved when needed and used for power generation or direct-use applications, such as district heating. It is important to identify potential issues associated with high-temperature reservoir thermal energy storage (HT-RTES) systems so that they can be mitigated, thus reducing the risks of these systems. This paper reviews past experiences from moderate and high-temperature reservoir thermal energy storage (RTES) projects, along with hot water and steam flood enhanced oil recovery (EOR) operations, to identify technical challenges encountered and evaluate possible ways to address them. Some of the identified technical problems that have impacted system performance include: 1) insufficient site characterization that failed to identify reservoir heterogeneity; 2) scaling resulting from precipitation of minerals having retrograde solubility that form with heating of formation brines; 3) corrosion from low pH or high salinity brines; 4) thermal breakthrough between hot and cold wells due to insufficient spacing. Proper design, characterization, construction, and operational practices can help reduce the risk of technical problems that could lead to reduced performance of these thermal energy storage systems.
Extraction of high-temperature geothermal resources from reservoirs is a challenge due to the complex interactions between temperature, permeability, and stress fields. Variations in physical fields are critical to thermal reservoir engineering. In this study, the coupling mechanism between temperature, permeability, and stress fields is systematically explored using theoretical analyses and numerical simulations, by utilizing the three-field coupling model. This study models the changes in porosity and permeability evolution during geothermal extraction, emphasizing the importance of the coupling term. The effects of pressure differences between injection and production wells, reservoir temperature variations, and fluid property changes on the temperature distribution and output thermal power within the geothermal reservoir were modeled and analyzed. The results reveal the significant effect of pressure differences between wells, and show that the geothermal extraction capacity of supercritical carbon dioxide (SC-CO2) is 1.83 times higher than that of water. Based on the statistical characteristics of the distribution pattern of natural fractures within the geothermal reservoir, the study simulated the distribution of natural fractures and developed a coupled THM model containing natural fractures. The results show that increasing the porosity of hydraulic and natural fractures can effectively increase the geothermal production capacity, especially the increase in the porosity of natural fractures is significant. These findings provide a key theoretical basis for understanding the THM coupling mechanism during geothermal extraction, and provide substantial support for optimizing the development and utilization of geothermal resources.
Seasonal warm and cold water storage in groundwater aquifers is a cost‐effective renewable energy technology for indoor heating and cooling. Simple dimensionless analytical solutions for the thermal recovery efficiency of Aquifer Thermal Energy Storage (ATES) systems are derived, subject to heat losses caused by thermal diffusion and mechanical dispersion. The analytical solutions pertain to transient pumping rates and storage durations, and multiple cycles of operation, and are applicable to various well configurations and thermal plume geometries. Heat losses to confining layers, its implications for optimizing plume geometries and aspect ratios, and heat spreading due to free convection are also discussed. This provides a general tool for broad and rapid assessment of aquifers and ATES systems. We show that if heat exchange with the confining layers is negligible, the thermal recovery efficiency of thermal plumes with cylindrical geometry is independent of the aquifer porosity and heat capacity C0. Therefore, if mechanical dispersion is negligible as is often the case, the only aquifer property that affects the recovery efficiency is the aquifer thermal conductivity. The field‐scale aquifer thermal conductivity λ can therefore be inferred from the recovery efficiency of a push‐pull heat recovery test. Remarkably, an increase in C0 could either increase, decrease, or not affect the recovery efficiency, depending on the thermal plume geometry. Hence, the analytical solutions reveal that the recovery efficiency is affected by complex interactions between the thermal plume geometry and aquifer properties. Approximate analytical solutions for subsurface temperature profiles over an entire ATES cycle are also derived.
