Study on the effect of well layout schemes and fracture parameters on the heat extraction performance of enhanced geothermal system in fractured reservoir

摘要

Well layout and fracture network in the enhanced geothermal system (EGS) jointly determine the fluid flow path, affecting the fluid flow and heat transfer process. It is necessary to investigate the optimal well layout and fracture parameter to get an efficient EGS. In this paper, the combination of multi-well layout and fracturing technology is conceptualized, a thermal-hydraulic coupling model is established to study the heat extraction performance under various multi-well layout schemes and fracture networks. Results show that the heat extraction ratio of Case 1 is highest, which is the optimal well layout under the research conditions. The fracture aperture is negatively correlated with heat extraction ratio. A higher fracture aperture is more likely to cause a short circuit and thermal breakthrough. The heat extraction ratio increases with the fracture length, while the growth rate decreases with the fracture length. Increasing the fracture number can improve the heat extraction performance to some extent, but excessive fractures can be counterproductive because they aggravate the interference among fractures. Under the research conditions, the preferable fracture aperture, length and number are 0.05 mm, 140 m and 114, respectively. This paper provides some reasonable suggestions for improving heat extraction performance from the perspectives of well layout and fracture network.