Investigation and evaluation methods of shallow geothermal energy considering the influences of fracture water flow

• Published in: Geothermal energy (Heidelberg) Vol. 11; no. 1; pp. 25 - 18
• Main Authors: Deng, Fengqiang, Pei, Peng, Ren, Yonglin, Luo, Tingting, Chen, Yixia
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 19.08.2023; Springer Nature B.V; SpringerOpen
• Subjects: Apertures; Boreholes; Convection; Earth and Environmental Science; Earth Sciences; Energy; Enthalpy; Evaluation; Fracture water; Fractured rock mass; Geoecology/Natural Processes; Geology; Geotechnical Engineering & Applied Earth Sciences; Geothermal energy; Geothermal power; Heat transfer; Heat treatment; Hydrogeology; Investigation and evaluation; Regional development; Renewable and Green Energy; Replenishment; Shallow geothermal; Water flow; Fractured rock mass; Investigation and evaluation; Fracture water; Shallow geothermal
• ISSN: 2195-9706; 2195-9706
• DOI: 10.1186/s40517-023-00267-1

The energy replenishment and heat convection induced by fracture water flowing through the rock mass impact the shallow geothermal energy occurrence, transfer and storage mechanisms in it. In this article, a suitability evaluation and categorization system is proposed by including judgement indexes that are more closely aligned with the actual hydrogeological conditions in fracture developed regions; an assessment approach of regional shallow geothermal energy is proposed by coupling the influences of fracture water into the calculation methods of geothermal capacity, thermal balance and heat transfer rate. Finally, by taking two typical fracture aperture distributions as examples, the impacts of fracture water on the investigation and evaluation of shallow geothermal energy are quantitatively analyzed. Although the fracture apertures only share 1.68% and 0.98% of the total length of a borehole, respectively, in the two examples, the fracture water convection contributes up to 11.01% and 6.81% of the total heat transfer rate; and the energy replenishment potential brought by the fracture water is equivalent to the total heat extraction of 262 boreholes. A single wide aperture fracture can dominate the aforementioned impacts. The research results can support more accurate evaluation and efficient recovery of shallow geothermal energy in fracture developed regions.