Experimental study on the breakdown mechanism of high temperature granite induced by liquid nitrogen fracturing: An implication to geothermal reservoirs

To reveal the breakdown mechanism of dry hot rock (HDR) induced by liquid nitrogen (LN) fracturing, laboratory tests were performed on high temperature granite using specialized apparatus. The pressure and fracture morphology granites subjected to different heating temperatures thermal treatments analyzed. results showed that decreased with increasing. As increased from 25 °C 300 °C, 40.63%. In addition, failure mode mainly presented in form tensile fractures, which developed into bi-wing fractures along hole axis. For higher than 220 an increase complexity temperature. After pre-cooled LN, was lowered enhanced. example, LN-treated sample 4.61%–27.70% lower heated sample. Under cryogenic conditions randomly distributed tiny cracks holes, made 8.67%–59.46%. LN fracturing could cause multiple cracking effects including (i.e., shock, damage cracking) pressure-induced HDR. Importantly, effect reduce improve complexity.