THERM project

Nowadays the necessity to produce CO2-neutral energy from renewable resources together with the growing societal needs in energy have motivated global efforts to optimize methods for extracting geothermal energy. To develop and test new technologies for energy production and storage in geothermal reservoirs, deep understanding about the role of heterogeneities on heat transport in fractured media is critically needed. To achieve a practically useful energy production capacity, the development of fractures within reservoirs is required at depth, where the rock temperature is sufficiently high for electric power generation. Such so-called enhanced geothermal systems (EGS) reservoirs, once hydraulically stimulated to increase their permeability, are expected to efficiently extract stored geothermal energy while providing high flow rates in production wells. As heat is transported towards the production wells by advection, only the connected flowing fractures are involved in diffusive heat transfer from the rock towards the fluid. One of the key characteristics responsible for the heat exchange efficiency between the working fluid (stream water and synthetic EGS analogues) and the surrounding rock, is the flow-wetted surface (FWS). The FWS describes the contact interface between flowing groundwater and the rock fracture surface over which heat transfer takes place and which is controlled by the associated flow pattern. The flow pattern, its evolution and its effects on heat production represents the major challenge in the assessments of EGS. The ambition of THERM is to enhance our understanding of flow, heat transport and associated thermo-hydro-mechanical processes occurring during the lifetime of a geothermal reservoir.