Velocity-dependent heat transfer controls temperature in fracture networks

Abstract

Heat transfer between a fluid and the surrounding rock in the subsurface is a crucial process not only, but most obviously, in geothermal systems. Heat transfer is described by Newton’s law of cooling, relating the heat transferred to a coefficient, the specific surface area, and the temperature difference between rock and fluid. However, parameterizing the heat transfer coefficient in fracture networks poses a major challenge. Here we show that within a fracture network the heat transfer coefficient is strongly heterogeneous but that laboratory single fracture experiments can provide a reasonable estimate in dependence of flow rate. We investigate the distribution of the heat transfer coefficient experimentally as well as numerically and analyze the heat transfer at individual fractures. Our results improve the prediction of temperatures in engineered and natural geothermal systems and allow sustainable management and design of reservoirs considering the role of individual fractures.

Hydrothermal Systems Characterized by Crustal Thermally‐dominated Structures of Southeastern China

“…Active faults are channels for underground geothermal water transport, enrichment and upwelling (Chen and Wang, 1994;Jolie et al, 2021) and plenty of natural thermal springs are located at the intersection point of fault zones (Curewitz and Karson, 1997;Jolie et al, 2021;Heinze and Pastore, 2023), suggesting that active faults have a major dominant role in the distribution of thermal springs. Since the late Cenozoic, crustal deformation in SE China has been quite frequent and prominent, the reactivation of preexisting faults cutting deeply into the strata of multiple geological ages (Li J H et al, 2014;Dong et al, 2020), rendering SE China to have viable conditions to form components such as geothermal sources, thermally-dominated structures and geothermal reservoirs, as well as hydrothermal convections.…”

Heat transfer characteristics of water flow through a single rock fracture: The combined effects of shear and surface roughness

“…The process of heated flow through fracture networks is complex owing to the anisotropic geometries of fractures. 4 Although the topic has been widely studied in recent years, it is still not completely understood even in the case of a single rough fracture. Flow and thermal modeling for single rough rock fractures is a fundamental problem for assessing the heat transfer through complex fracture networks.…”

“…A comprehensive understanding of heat transfer of fluid flow through fractured rock is crucial for geothermal reservoir management in terms of optimizing heat extraction and improving the heat‐recovery factor of geothermal reservoirs. The process of heated flow through fracture networks is complex owing to the anisotropic geometries of fractures 4 . Although the topic has been widely studied in recent years, it is still not completely understood even in the case of a single rough fracture.…”