We have recently proposed a novel Enhanced Geothermal System (EGS) that addresses the difficulties of traditional EGSs. Conventional EGSs are typically not commercially successful because of the low thermal diffusivity of hot dry rock and the horizontal EGS geometry, which collectively hinder recharge in produced geothermal reservoirs. The challenge is to find or create sufficient rock permeability and to visualize accurately this permeability field to which a high efficiency heat exchanger can be tailored. RAD-EGS mimics naturally occurring hydrothermal systems, which contrary to EGS have frequently been proven to be economically sustainable. The RAD-EGS creates a vertically oriented heat exchanger or vane in the deep subsurface. This vane mimics a radiator in an internal combustion engine. Water is injected at the bottom of the vane and produced on top. Currently available subsurface imaging technology suggests that RAD-EGS be built in Hot Sedimentary Aquifers (HSA) using propellant fracking to create high permeability vane(s) in the plane defined by SHmax and S1 (vertical). We have performed 3D heat transfer simulations in order to evaluate the RAD-EGS in a HSA. The simulations account for subsurface heterogeneity including the presence of underlying basement rock, an overlying confining layer, and an ambient horizontal hydraulic gradient. The simulated 3D fields of fluid pressure and velocity as well as temperature provide crucial information about the effluent temperature of the injected coolant and the pressure differential needed to maintain the circulation of the coolant as a function of time. These results allow evaluation of the efficiency of RAD-EGS. Our simulations indicate that the proposed induced upward flow in the vane can significantly prolong the lifetime of RAD-EGS when compared to downward flow. Specifically, produced fluid temperatures greater than 150°C that are required for commercial energy production can be maintained for significantly longer periods of time for upward flow. This suggests that mimicking a natural hydrothermal system is a successful EGS strategy. Recharge due to heat advection in the surrounding water-saturated aquifer also prolongs substantially the lifetime of the thermal reservoir. RAD-EGS does not suffer from fluid losses that can be substantial for EGS built in hot dry rock (HDR).

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