Recent advances in geothermal energy reservoirs modeling: Challenges and potential of thermo-fluid integrated models for reservoir heat extraction and geothermal energy piles design

The sustainable utilization of geothermal resources is intimately connected to an accurate assessment of ground thermal response to energy injection/extraction. In this context, the optimization strategies and sizing methodologies are calculated from the balance of the reservoir's energy demand. Therefore, accurate numerical modeling of the thermodynamic behavior of the ground heat exchanger is crucial for the optimal design of geothermal reservoirs. Herein, the methods of numerical modeling of geothermal systems as a framework for the sizing and design of geothermal plants are presented. Moreover, a critical review of geothermal reservoir modeling for heat extraction purposes is outlined. Different numerical methods, such as the finite element method, finite difference method, finite volume method, etc., which are used to simulate and describe the heat transfer extraction of geothermal wells, geothermal reservoirs, and geothermal energy piles are discussed. Furthermore, a general methodological perspective of integrated analysis is presented in an overview of the limits of the reservoir simulation. Moreover, the recent advances in various parameters affecting the heat extraction performance of geothermal heat exchangers including pipe diameter, pipe arrangement, pipe pitch, center-to-center distance, pipe material, pipe length, and borehole depth are also discussed. This paper can be regarded as a decision-making tool and provide a useful pathway for sizing parameters selection and sustainable geothermal utilization system.