Speaker
Description
Geothermal energy has gained increasing attention in recent years as a sustainable and low-carbon energy source. Many geothermal systems are hosted in highly fractured rocks, whose simulation requires robust modelling that is capable of handling strongly coupled and nonlinear processes of fluid flow and heat transfer. The complex geometry and hydrodynamic characteristics of fracture networks add to the aforementioned challenge. All these features, exacerbated by the strong contrast between fracture and matrix properties, make an accurate representation of fracture–matrix heat exchange essential.
Several modelling strategies have been developed to address these challenges. Implicit approaches, based on upscaling effective medium properties, offer computational efficiency but often fail to capture localized fracture–matrix interactions. In contrast, explicit approaches such as Discrete Fracture Matrix (DFM) models represent fractures and matrix explicitly, providing higher accuracy, but at the cost of significantly increased computational time, especially for densely fractured reservoirs.
In this work, we investigate an efficient hybrid modelling framework for flow and heat transfer in fractured porous media that combines elements of both explicit and implicit approaches. The proposed Discrete Fracture Network–Dual Porosity (DFNDP) formulation explicitly represents fractures as lower-dimensional elements, with fluid flow restricted to the fracture network, while heat exchange between fractures and the surrounding matrix is modelled through a semi-empirical exchange coefficient derived under a steady-state approximation.
The DFNDP model is validated against a DFM reference model over a range of fracture densities and flow conditions spanning diffusion- to advection-dominated regimes (low to high Péclet numbers). Quantitative comparisons based on temperature evolution curves within the fractures demonstrate that the DFNDP approach accurately reproduces DFM results, with improved agreement in advection-dominated regimes (high Péclet numbers). The accuracy is further enhanced as fracture density increases, corresponding to the targeted applications in highly fractured geothermal reservoirs. Moreover, the DFNDP model achieves a computational speedup of approximately two to five times compared to DFM. These efficiency gains increase as fracture density rises, while good accuracy is still maintained. The extension of the approach toward time-dependent fracture-matrix exchange coefficients will be investigated as well.
| Country | France |
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