An improved closed-loop heat extraction method from geothermal resources

Disposal of produced water and induced earthquakes are two major issues that have endangered development of the geothermal energy as a renewable source of energy. To avoid these problems, circulation of a low-boiling working fluid in a closed loop has been proposed; however; since the major mechanism in this method for heat extraction is conduction rather than convection and additionally the heat conduction is limited to the wellbore surface. To overcome this shortcoming, the formation can be fractured with high conductivity material (for instance, silicon carbide ceramic proppants or cements with silane and silica fume as admixtures) to artificially increase the contact area between the "working fluid" and the reservoir. Our calculations show that fracturing increases the contact area by thousand times, additionally, the fracturing materials reinforce and stressed the formation, which reduce the risk of seismic activity due to temperature or pressure changes of the system during the production.