Numerical simulation of a comparative study on heat extraction from Soultz-sous-For\^ets geothermal field using supercritical carbon dioxide and water as a working fluid

Geothermal energy is an infinite energy source for the present human society. Energy extraction from the deep subsurface requires engineering using a working fluid that circulates between well doublet. Due to its thermal properties, CO2 is an ideal option as a heat transfer fluid. By using CO2, working fluid loss is an advantage compared to other working fluids. This study developed a field-scale hydro-thermal model to examine the heat extraction potential from Soultz-sous-For\^ets with CO2 as the working fluid. Results are compared for the same scenario with water as the working fluid. A better understanding of the heat extraction mechanism is established by considering the reservoir response and the wellbore heat exchange. Sensitivity analyses are performed for different injection temperatures and flow rates for 50 years. Results show that the wellbore effect is multiple times higher than the reservoir response to the production temperature. Furthermore, lowering the injection temperature eventuates to a smaller temperature reduction at the subsurface, enhancing the overall heat extraction potential with a minor impact on thermal breakthrough. The cold region developed around the injection wellbore may affect the production fluid temperature due to its proximity to the production wellbore. To reach higher heat extraction efficiency, it is essential to use sufficient wellbore spacing. CO2 can be used as working fluid for over 50 years as it does not show significant thermal breakthrough and temperature plume evolution in the reservoir under studied conditions. CO2 shows lower temperature reduction for all injection rates and temperatures for 50 years of operation.Comment: 17 pages, 8 figure

Heat Extraction in Geothermal Systems with Variable Thermo-Poroelastic Fracture Apertures

The fracture network largely determines the efficiency of heat extraction from fractured geothermal reservoirs. Fracture openings are influenced by thermo-poroelastic stresses during cold fluid flow, with the interplay between fracture length and fracture opening regulating heat transfer. The lack of field data concerning fluctuating fracture openings underscores the necessity for computational models. This work emphasizes the impact of such gaps in the literature. Factors such as temperature, pressure, stress, thermal breakthrough time, and cumulative energy are evaluated to analyze the system’s behavior. A sensitivity analysis is employed to ascertain the significance of stress on fracture opening, compared with thermo-hydraulic behavior. The results show that stress field alterations, due to intersections with minor fractures, can cause up to a 15% variation in the largest fracture’s opening. The impact of thermoelastic stress outweighs the impact of poroelastic stress approximately threefold. Such stress-induced variations in fracture openings can lead to an up to 30% increase in cumulative heat extraction, while the drop in production temperature is limited to around 50%

Hydro-Thermal Modeling for Geothermal Energy Extraction from Soultz-sous-Forêts, France

The deep geothermal energy project at Soultz-sous-Forêts is located in the Upper Rhine Graben, France. As part of the Multidisciplinary and multi-contact demonstration of EGS exploration and Exploitation Techniques and potentials (MEET) project, this study aimed to evaluate the possibility of extracting higher amounts of energy from the existing industrial infrastructure. To achieve this objective, the effect of reinjecting fluid at lower temperature than the current fluid injection temperature of 70 °C was modeled and the drop in the production wellhead temperature for 100 years of operation was quantified. Two injection-production rate scenarios were considered and compared for their effect on overall production wellhead temperature. For each scenario, reinjection temperatures of 40, 50, and 60 °C were chosen and compared with the 70 °C injection case. For the lower production rate scenario, the results show that the production wellhead temperature is approximately 1–1.5 °C higher than for the higher production rate scenario after 100 years of operation. In conclusion, no significant thermal breakthrough was observed with the applied flow rates and lowered injection temperatures even after 100 years of operation

Comparison of Simulated Annealing, Genetic, and Tabu Search Algorithms for Fracture Network Modeling

The mathematical modeling of fracture networks is critical for the exploration and development of natural resources. Fractures can help the production of petroleum, water, and geothermal energy. They also greatly influence the drainage and production of methane gas from coal beds. Orientation and spatial distribution of fractures in rocks are important factors in controlling fluid flow. The objective function recently developed by Masihi et al. 2007 was used herein to generate fracture models that incorporate field observations. To extend this method, simulated annealing, genetic, and tabu search algorithms were employed in the modeling of fracture networks. The effectiveness of each algorithm was compared and the applicability of the methodology was assessed through a case study. It is concluded that the fracture model generated by simulated annealing is better compared to those generated by genetic and tabu search algorithms

Comparison of Simulated Annealing, Genetic, and Tabu Search Algorithms for Fracture Network Modeling

Abstract The mathematical modeling of fracture networks is critical for the exploration and development of natural resources. Fractures can help the production of petroleum, water, and geothermal energy. They also greatly influence the drainage and production of methane gas from coal beds. Orientation and spatial distribution of fractures in rocks are important factors in controlling fluid flow. The objective function recently developed b

Antibacterial activity of Avicennia marina leaves extract on Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa

Background: Antibiotic resistance is one of the most common problems in medicine. Therefore discovering of new antibacterial components with least side effect is necessary. Based on the presence of biologically active constituents in Avicennia marina and its uses in alternative medicine, it is supposed that this plant has antibacterial effect. Methods: This study was designed as an "in vitro" study. In extraction procedure, 20% glycerin solution was utilized as solvent. In the screening step, S. aureus (ATCC 25923), E. coli (ATCC 25922) and P. aeruginosa (ATCC 27853) were exposed to extract with 90 mg/ml in concentration, separately. Thereafter, these three strains were examined with different concentrations of the extract to determine minimal bactericidal concentration (MBC). Also the effect of MBC was tested at time zero and after incubation time ranging from 2 to 24 hours. Results: The MBCs on S. aureus, E. coli and P. aeruginosa were 7.9, 33.8 and 15.8 mg/ml, respectively. The minimum times necessary for effectiveness of extract were as follows: 24h for S. aureus, 8h for E. coli and 12h for P. aeruginosa. Conclusion: Avicennia marina leaves extract has a significant antibacterial effect on E. coli and P. aeruginosa as gram negative bacteria, and S. aureus as a gram positive bacterium

Database to “Impact of the fracture aperture changes through the fully coupled thermoporoelastic stress on the heat extraction from a fractured reservoir”

Heat production from geothermal reservoirs is controlled by coupled thermo-hydro-mechanical processes and thermal expansion coefficient plays an important role in deciding the fracture aperture. To provide insights on the thermal expansion coefficient values with respect to temperature, two types of sandstones are considered: Remlinger and Flechtinger obtained from Steinbruch, Germany. Measurements are performed with Linseis L75 instrument and the core sample length is 5.26 mm