Adapted numerical modelling strategy developed to support EGS deployment.
Résumé
The exploitation of Enhanced/Engineered Geothermal Systems (EGS), for electricity and/or heat production, is a promising way to increase the amount of renewable energies contribution in the energetic mix in Europe. In regard to the required production characteristics (production temperature and flowrate) for the economical viability of EGS, the favourable targeted geological systems are deep and fractured. In order to reduce the risks and the prohibitive costs linked to the depth of such geothermal systems, numerical modelling is a useful tool to understand such deep fractured systems and to help in the construction and in the management of the deep infrastructures (wells architecture, stimulation of wells, implementation of adapted network of wells). Nevertheless, this forces to a change of paradigm in comparison to « classical » reservoir modelling based on mechanics of continuum media. Indeed 3D Discrete Fracture Network (DFN) approach looks fairly adapted to catch the mechanical and hydraulic phenomena in the fractured rock mass around wells and to understand the global systems in the network of wells. The conceptualisation of the fractured rock mass is a crucial step for such DFN models not only for the geometry but also to constrain the constitutive behaviour of singularities (fault zones, fractures etc.), depending on the tectonic context. We present some results illustrating how DFNs can be used to study the EGS behaviour at several scales.