Hello Matteo
I don't think that feflow is suitable to model a standing column well like that you posted. In that case the most relevant process to simulate is the convection flow inside the well pipe.
However, perhaps you could find interesting the feflow simulation of an open loop comprising two wells, one for pumping and the other for injecting water after heat exchanging. The following are the links
http://www.regione.emilia-romagna.it/wcm/geologia/canali/geotermia/progetti/01_geotermia_rer/01_caso_studio.pdf
http://www.regione.emilia-romagna.it/wcm/geologia/canali/geotermia/progetti/01_geotermia_rer/03_spunti_riflessione.pdf
If you are interested I can send you or upload the .fem files of the simulations.
Best luck. Gianmarco
