Numerical investigation of closed-loop heat extraction in different-layout geothermal wells with particular reference to thermal interference analyses

Harnessing geothermal energy through closed-loop heat extraction in deep geothermal wells for building heating in dense urban residential areas is a challenge, especially when the spare surface area is very limited for arranging the wellheads. In this study, 3-D models of closed-loop heat extraction in vertical, L- and deviated wells are established. It is found that, when the wellhead spacing is 5 m, there is almost no thermal interference among the symmetrically-arranged deviated wells, indicating that the deviated well clusters have obvious advantages over the vertical well clusters. At the end of the first heating season, the heat extraction rate of the four deviated well cluster (FDS) is 246 kW higher than that of the four vertical well cluster (FVS). The heat extraction rate of FDS exceeds that of the five vertical well cluster. After 10-year operation, the heat extraction rate of the FDS is 350 kW higher than that of FVS. When the wellhead spacing of FVS exceeds 80 m, the thermal interference factor (TIF) is less than 0.19 %, equivalent to the degree of the thermal interference among the wells of FDS with a wellhead spacing of 5 m. The results obtained in this study are of engineering-guiding significance for geothermal industries.