Improving the geometric topology of geothermal heat exchangers in oil bore-holes

Abstract

A review has been conducted of key trends in the development of geometric topology of geothermal heat exchangers. Authors proposed approaches to improving the designs and network structures for heattransfer media circulation in the bottom-hole space of oil-and-gas reservoirs. Four geometric topologies of geothermal heat exchangers have been analysed: І-ІІ-rectilinear vertical smooth and finned pipelines; ІІІ-IV-a cluster in the form of a set of smooth and finned single-pipe elements, representing a figure of "squirrel wheel" or "meridian sphere" type. It is shown that the most effective technical solution, which ensures the increase in the coefficient of performance (COP) of borehole geothermal systems is finning the heat exchanging pipes. For the heat exchangers of І-ІІ type, the calculated increase in COP in comparison with smooth pipes is 40%, and for ІІІ-IV type-95%. The key parameters influencing the COP of a geothermal heat exchanger are: the radius of fluids draining out during the heat exchange process, the radius of pipelines with circulating heat-transfer medium, the diameter of a cluster heat exchanger, the heat exchange area, the parameters of rocks thermal resistance in the bottom-hole zone of heat-receiving.