Evaluation of heat exchange in a geothermal well

Abstract

The heat flux and heat exchange in a well play an important role in the energy extraction from a geothermal system. We have evaluated the possibility of heat mining without any fluid extraction from a deep well, in order to assess the technical and economical possibility for such an exploitation approach, where there is no effective interaction from the deep circulation (if any) and the operative fluid in the power plant itself, with the only exception of energy transfer through heat exchange on the well surface. A simplified system has been modelled, with an impermeable coverage, a given geothermal gradient and and a deep layer, with different level of permeability, ranging from a full conductive to a partial convective model. The analytical solution was calculated and it has been used to check the results with a 2D model using TOUGH2 software, and after the calibration process it was possible to perform a full range of simulations in different conditions.