Some Results Useful to Achieve Stable Control of an Artificial Geothermal Crack in Hot Dry Rocks

Abstract

An abundant amount of geothermal energy could be recovered from hot dry rocks by circulating fluid through geothermal cracks created by a hydraulic fracturing technique. During the extraction of heat, the surface of geothermal cracks are cooled by circulating fluid and the thermal contraction of the rocks occurs. Therefore, to control the geothermal cracks, it is necessary to make a fracture mechanics study including thermoelastic effects. In this paper, thermoelastic analysis is made for an artificial geothermal crack in a hot dry rock. Discussion is focused on the behavior of an artificial geothermal crack during extraction of heat. First, we concern ourselves with the effect of the initial rock temperature gradient on the fluid temperature at the outlet and the behavior of the geothermal crack. Next, the effect of the change of injection flow rate is considered. Finally, the time limit for the stable geothermal crack is discussed. The results may be useful to achieve stable control of geothermal cracks in hot dry rocks.