An experimental investigation into the characteristics of hydraulic fracturing and fracture permeability after hydraulic fracturing in granite

Geothermal energy, as a renewable energy source, can meet the growing need for energy associated with low atmospheric emissions. Hydraulic fracturing is a promising simulation technique used in enhanced geothermal systems to increase heat production from a geothermal reservoir by enhancing reservoir rock permeability. This paper presents an experimental study on hydraulic fracturing of granite which is the most suitable hot dry rock type focusing on the effects of confining stress, water injection flowrate, and temperature on breakdown pressure and fracture permeability. Results indicate that the rock temperature is one of the more important factors affecting hydraulic breakdown pressure. The breakdown pressure increases with the increase of confining pressure. Additionally, as the injection flow rate increases, the breakdown pressure increases. In addition, the fracture permeability after hydraulic fracturing is calculated on the basic of pressure data recorded during hydraulic fracturing. The results can provide some guidance to those seeking to implement economical and reasonable hydraulic fracturing simulations and improve heat production capacity in EGS. (C) 2019 Elsevier Ltd. All rights reserved.