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Numerical Modeling of Deep Geothermal Energy Extraction from Hot Dry Rock Reservoirs by Considering the Heterogeneity and Anisotropy of the Reservoir

Akbari Khoei, Mohammad Ali | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57306 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Pak, Ali
  7. Abstract:
  8. As global temperatures are progressively rising and climate change is affecting the occurrence of droughts and floods throughout the world, the use of green and renewable energy sources, including geothermal energy, has become more prevalent to reduce the emissions of greenhouse gases and carbon dioxide in the atmosphere. To investigate the possibility of utilizing deep geothermal energy, field, experimental, and numerical studies are required. Due to the lack of field and experimental data regarding deep geothermal energy reservoirs, numerical modeling is necessary in order to evaluate their performance. Numerical analysis using a coupled thermal-hydraulic-mechanical approach was conducted in this study. A comparison of the model results with those of the technical literature has been undertaken to determine the model's validity, and it has been demonstrated that the proposed model in Comsol Multiphysics is precise enough to study the thermal-hydraulic-mechanical behavior of deep geothermal reservoirs, and therefore, was used in all numerical simulations in this study. By analysing the effects of anisotropy and heterogeneity on the performance of Hot Dry Rock (HDR) reservoirs, it is demonstrated that mechanical and thermal anisotropies, and heterogeneities, have negligible effects on the performance of HDR reservoirs. However, it is important to consider the hydraulic heterogeneity when analyzing a system, since it can significantly affect the behavior of the geothermal system, which may result in significant reductions in production temperature, thermal power output, and reservoir service life. Moreover, It has also shown that deep geothermal energy extraction can impose some environmental impacts on its surrounding environment such as ground deformations. According to the results of the conducted study, reservoir displacement increases with increasing the hydraulic heterogeneity of the reservoir, making it an important factor to be considered when modeling deep geothermal energy extraction from HDR reservoirs. Furthermore, the optimal drilling scenario was identified based on twenty injection and production scenarios in layered geothermal reservoirs to optimize the behavior of heterogeneous geothermal reservoirs, and was shown that drilling both types of wellbores into the least permeable layer leads to better heat extraction performance. Recent years have seen an increase in the use of geothermal systems that consist of horizontal wellbores. Therefore, a novel L-shaped wellbore system that is commonly used in the oil and gas industry is proposed and investigated. According to the results, the efficiency of the proposed wellbores increases as the horizontal section length increases. In addition, even though the proposed wellbores lead to higher displacements above the reservoir compared to the vertical wellbores, they significantly increase the reservoir's service life, production temperature, and thermal power output. After all, It was observed that increasing the injection pressure of the L-shaped wellbores results in a greater heat extraction ratio, according to sensitivity analysis conducted on the injection pressure
  9. Keywords:
  10. Deep Geothermal Reservoir ; Coupled Thermohydromechanical (THM)Analysis ; Anisotropy ; Reservoir Heterogeneity ; Horizontal Wells ; Geothermal Energy ; Hot Dry Rock Reservoirs

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