Simulation analysis of a single well geothermal system with open-loop structure

Abstract

The relatively small heat exchange power limits the promotion and application of deep borehole heat exchanger (DBHE) with the closed loop due to the main heat transfer pattern of heat conduction through rocks with poor thermal conductivity coefficient. Furthermore, geothermal water is prohibited to extract in some places even with 100% reinjection. To solve the above problems, here a novel single-well enhanced geothermal system (SEGS) is studied with an open-loop structure having the convection heat exchange process. The heat transfer performance, mechanism and main influential factors of SEGS are studied. Result shows that the heat transfer performance of SEGS is greatly improved compared to DBHE, and the average heat transfer power of SEGS reaches 1603.6 kW and 1204.6 kW respectively with different operation modes. In addition, the study also finds that the convective heat transfer process inside the geothermal reservoir is simultaneously affected by the driving effect of the fluid in the screen and the buoyancy effect. Further, the above two effects act in the same direction when the annulus is used as the inlet, while they act in the opposite direction when the inner tube is used as the inlet.