Numerical investigation on the effects of the fracture network pattern on the heat extraction capacity for dual horizontal wells in enhanced geothermal systems

Abstract

In an enhanced geothermal system (EGS), fractures and fracture networks are the predominant elements for fluid flow and heat transfer through the artificial reservoir. In this work, different conceptual discrete fracture networks were generated by characterizing the fracture number, fracture bifurcation and fracture connectivity of the fracturing area. A thermal–hydraulic (TH) coupled mathematical model was applied to evaluate the EGS thermal recovery process. Heat extraction capacity was appraised in terms of the temperature production, net power generation and thermal recovery rate. The results show that an interconnected fracture network with considerable bifurcation results in high heat production and power generation, however the energy efficiency is not optimized due to water loss. The effect of fracture connectivity is more significant than that of fracture spacing. The more fractures (bifurcations) the higher the overall and local heat recovery rates near the production well. For the case with connected fractures without bifurcation, the less characteristic length in the direction of flow results in a lower heat production and power generation.