Exploiting the renewable energy rather than fossilfuels has become increasingly important. Among all types of renewable energy, geothermal energy is an ideal choice . It can be used for heating and generating electricity and has advantages over wind and solar power [2, 3]. Closed-loop technology can be used to effectively extract heat from the underground formation and can avoid problems of corrosion, scaling in the wellbore, and mass flowrate loss in the reservoir . Rybach and Hopkirk, firstly proposed the concept of using coaxial heat exchanger to provide heat for buildings in 1995 . Alimonti et al. once set up a numerical model of a coaxial heat exchanger to maximize the extracted heat on Villafortuna Trecate oilfield . Bu et al. made a study on acquiring geothermal energy from an abandoned oil and gas well using coaxial heat exchanger and verified its feasibility . Noorollahi et al. carried out a numerical simulation of two vertical closed-loop heat extraction models for two oil wells in southern Iran .
However, few studies investigated the performance of closed-loop heat extraction from deviated-geothermal wells. In this paper, Closed-loop heat extraction models for a vertical geothermal well (Model A), a deviated geothermal well (Model B) and symmetrically arranged two deviated-geothermal wells (Model C) have been established. Their heat extraction performances were compared with respect to different inflow parameters.
Keywords closed-loop heat extraction, deviated-geothermal wells, numerical simulation