Heat extraction performance evaluation of U-shaped well geothermal production system under different well-layout parameters and engineering schemes

The U-shaped well geothermal production system is proposed on the basis of abandoned oil wells which can achieve the non-interference conversion of "heat extraction without water". Compared with the fracturing enhanced geothermal system, the U-shaped well system is more stable and more achievable. However, there is no comprehensive parametric study of the heat extraction performance of U-shaped well geothermal production system. In this paper, the thermal-hydraulic model of U-shaped geothermal production system is established based on the abandoned oil well. The temporal and spatial evolution of temperature field is analyzed, radiation range of the temperature drop is calculated, the effects of well-layout parameters on heat extraction performance are investigated. For well-layout parameters, the optimal horizontal section length is 1500m, the optimal insulation material length is 1000m. For the engineering parameters, the optimal injection rate is 1500m(3)/d and the optimal injection fluid temperature is 288.15K to obtain a higher heat extraction power. The discontinuous mode can sustainably guarantee better heat extraction performance compared with continuous mode. These findings can provide some reasonable suggestions for the deep geothermal development.