scholarly journals The Potential of Depleted Oil Reservoirs for High-Temperature Storage Systems

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6510
Author(s):  
Kai Stricker ◽  
Jens C. Grimmer ◽  
Robert Egert ◽  
Judith Bremer ◽  
Maziar Gholami Korzani ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Energy ◽  
Storage Capacity ◽  
Storage Systems ◽  
Storage Conditions ◽  
Oil Reservoirs ◽  
Upper Rhine Graben ◽  
Operational Conditions ◽  
Temperature Excess ◽  
Storage Potential

HT-ATES (high-temperature aquifer thermal energy storage) systems are a future option to shift large amounts of high-temperature excess heat from summer to winter using the deep underground. Among others, water-bearing reservoirs in former hydrocarbon formations show favorable storage conditions for HT-ATES locations. This study characterizes these reservoirs in the Upper Rhine Graben (URG) and quantifies their heat storage potential numerically. Assuming a doublet system with seasonal injection and production cycles, injection at 140 °C in a typical 70 °C reservoir leads to an annual storage capacity of up to 12 GWh and significant recovery efficiencies increasing up to 82% after ten years of operation. Our numerical modeling-based sensitivity analysis of operational conditions identifies the specific underground conditions as well as drilling configuration (horizontal/vertical) as the most influencing parameters. With about 90% of the investigated reservoirs in the URG transferable into HT-ATES, our analyses reveal a large storage potential of these well-explored oil fields. In summary, it points to a total storage capacity in depleted oil reservoirs of approximately 10 TWh a−1, which is a considerable portion of the thermal energy needs in this area.

Numerical investigation of induced thermal impacts from high-temperature thermal energy storage in porous aquifers

2021 ◽  
Author(s):  
Bo Wang ◽  
Jens-Olaf Delfs ◽  
Christof Beyer ◽  
Sebastian Bauer
Keyword(s):  
High Temperature ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage Capacity ◽  
Storage Temperature ◽  
Thermal Recovery ◽  
Pumping Rate ◽  
Background Temperature ◽  
C 30

<p>High-temperature aquifer thermal energy storage (HT-ATES) in the geological subsurface will affect the temperature distribution in and close to the storage site, with potential impacts on groundwater flow and biogeochemistry. Quantification of the subsurface space affected by a HT-ATES operation is thus required as one basis for urban subsurface space planning, which would allow to address potential competitive and conflicting uses of the urban subsurface. Therefore, this study shows a quantitative evaluation of induced thermal impacts and subsurface space required for a synthetic ATES operated at varying temperature levels.</p><p>A hypothetic seasonal HT-ATES operation is simulated using the coupled groundwater flow and heat transport code OpenGeoSys. A well doublet system consisting of fully screened “warm” and “cold” wells 500 m apart is used for the storage operation. A sandy aquifer typical for the North German Basin at a depth of 110 m and with a thickness of 20 m in between two confining impermeable layers is used as storage formation. Seasonal cyclic storage is simulated for 20 years, assuming charging and discharging for six months each. During charging, water with the aquifer background temperature of 13°C is extracted at the "cold" well, heated to 70°C and reinjected at the “warm” well using a pumping rate of 30 m³/h. During discharging, the stored hot water is retrieved at the "warm" well using the same pumping rate and reinjected at the “cold” well after heat extraction at aquifer background temperature.</p><p>The simulation results show that during a single storage cycle using a storage temperature of 70°C 7.51 GWh of thermal energy is injected, of which 4.79 GWh can be retrieved. This corresponds to a thermal recovery factor of 63.8% and thus an effective storage capacity of 0.43 kWh/m<sup>3</sup>/K can be deduced in relation to the heat capacity of the storage medium. For storage temperatures of 18°C, 30°C and 50°C, the effective storage capacity is 0.56 kWh/m<sup>3</sup>/K, 0.55 kWh/m<sup>3</sup>/K and 0.49 kWh/m<sup>3</sup>/K, respectively. By delineating the subsurface volume with a temperature increase larger than 1°C, the subsurface space used for and affected by the storage operation at the storage temperature of 70 °C is determined to be 10.56 million m³. In relation to the retrieved thermal energy, a subsurface volume of 2.2 m<sup>3 </sup>is thus required to retrieve one kWh of heat energy at 70 °C injection temperature. At lower temperatures of 18°C, 30°C and 50°C, the subsurface space required is 1.77 m<sup>3</sup>/kWh, 1.54 m<sup>3</sup>/kWh and 1.76 m<sup>3</sup>/kWh, respectively. The lower effective storage capacity and the relatively larger required space, which correspond to a lower thermal recovery factor, are caused by induced thermal convection and higher heat losses by conduction at higher temperatures.</p>

scholarly journals Coarse-Grained Model of Underground Thermal Energy Storage Applied to Efficiency Optimization

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1918
Author(s):  
Anders E. Carlsson
Keyword(s):  
Water Flow ◽  
Thermal Energy ◽  
Time Course ◽  
Storage Capacity ◽  
Storage Systems ◽  
Renewable Energy Sources ◽  
Coarse Grained ◽  
Energy Sources ◽  
Efficiency Optimization ◽  
Coarse Grained Model

Seasonal storage of thermal energy, by pumping heated water through a borehole array in the summer, and reversing the water flow to extract heat in the winter, can ameliorate some of the intermittency of renewable energy sources. Simulation can be a valuable tool in enhancing the efficiency of such storage systems. This paper develops a simple, efficient mathematical model of spatial temperature dynamics that focuses on the radial water flow in a cylindrical borehole array. The model calculates the time course of the temperature difference between outgoing and incoming water accurately, and allows new optimization strategies to be explored easily. A strategy based on discharging water heated by the array before it reaches the array center can increase the storage capacity by 25% for a system with a 20% smaller radius than the well-studied Drake Landing system. If the density of boreholes is also doubled, the improvement is 29%.

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