Study of stimulation mechanism of hydraulic fracturing induced thermal shock on joint system of geothermal reservoirs.

Hydraulic fracturing has been prevailingly applied to induce thermal shock in geothermal reservoirs for the utilization of geothermal energy. With natural joints commonly distribute in the reservoirs, the stimulation mechanism of thermal shock on joint system is inevitably investigated at fracturing initiation stage to enlarge heat transfer space. In this paper, the interaction of hydraulic fractures (HFs) and joints was simulated by lattice-spring method (LSM). The factors of fluid viscosities, shock times, approaching angles, and joint sets were analyzed to reveal the stimulation effect of thermal shock. The results present that orthogonal approaching angle, moderate shock times, and low fluid viscosity are beneficial to the creation of heat transfer space. The radius of expansion region of the thermal shock is around 1 m, in which the interaction behavior of HFs mainly consists of arrest and penetration. This research aims at revealing the stimulation mechanism of thermal shock on joints and therefore improving the treatment of hydraulic fracturing in geothermal energy development.