Numerical calculation of heat transfer in single medium-deep geothermal well

Medium-deep geothermal single well heat transfer is a technology of developing geothermal energy to "obtain heat without extracting groundwater". This technology has the advantages of not damaging the groundwater environment and taking more heat. However, there are few studies on the numerical calculation of single well heat transfer above 3000m depth. In this paper, based on the geothermal geological conditions in Xi'an, the numerical method was used to calculate the heat transfer of a medium-deep geothermal single well with different well structures (L-shaped directional wells and cluster directional wells) under the scenario of continuous operation of a heating season. The results show that under the same flow rate and geothermal gradient, the outlet temperature, heat taken per unit time and the heat taken by the extended meter in the L-shaped directional wells are higher than that of cluster directional wells after 120 days of continuous operation. At the same flow rate, the higher the geothermal gradient, the higher the outlet temperature, and the greater the heat value per unit time and the heat by the extended meter. Under the same geothermal gradient, the higher the flow rate, the lower the outlet temperature, and the greater the heat per unit time and the heat by the extended meter are. In cluster directional wells, the outlet temperature, the heat per unit time, and the heat by extended meter at 30° inclination was higher than that at 45°inclination.With the increase of flow rate, the difference of outlet temperature, heat per unit time and heat by extended meter under two kinds of deviations decreased gradually. Considering the outlet temperature, heat per unit time and heat by extended mete, the heat transfer of L-type directional wells was better than that of cluster directional wells; from the point of view of the difficulty of drilling operation, cluster directional wells are better than L-type directional wells; in two kinds of deviation structures of cluster directional wells, cluster directional wells with 30°inclination are better than 45°inclination. Therefore, the calculated results under different working conditions can provide a reference for the development and utilization of medium-deep geotherm