This paper aims to investigate the effect of thermal shock on hydraulic fracturing in hot dry rock (HDR). To simulate the thermal shock effect caused during the injection of cold water, several natural granite specimens were slowly heated to various target temperatures and then rapidly cooled down by flowing water. Laboratory hydraulic fracturing experiments were performed on granite specimens under triaxial stress condition and room temperature. After that, computed tomography (CT) scanning technique, scanning electron microscope (SEM) observation, and surface profile scanning (SPS) tests were combined to analyze the influence of thermal shock on fracture morphology from micro-scale to macro-scale. Moreover, the characteristics of injection pressure curve were discussed. Experimental results show that a single main hydraulic fracture with large aperture is created and approximately propagates along the direction perpendicular to the minimum principal stress before 300 °C. When the thermal treatment temperature is higher than 300 °C, multiple hydraulic fractures with branches tend to be created due to the existence of thermally-induced damage zone near the well hole. Experimental results of SPS tests indicate that the maximum height difference of the hydraulic fracture surface increases with increasing thermal treatment temperature. The tortuosity of hydraulic fracture significantly increases when the thermal treatment temperature is higher than 300 °C. Additionally, the analysis of injection pressure response shows that apparent non-linear pressurization, and decrease in pressurization rate and breakdown pressure are observed after 300 °C.

本文旨在研究热冲击对热干岩（HDR）中水力压裂的影响。为了模拟冷水注入过程中引起的热冲击效果，将几个天然花岗岩样品缓慢加热到各种目标温度，然后通过流动的水快速冷却。在三轴应力条件和室温下，对花岗岩试样进行了实验室水力压裂实验。之后，结合计算机断层扫描（CT）扫描技术，扫描电子显微镜（SEM）观察和表面轮廓扫描（SPS）测试，从微观到宏观分析热冲击对断裂形态的影响。此外，还讨论了注射压力曲线的特性。实验结果表明，在300°C之前，产生了一个具有大孔径的单一主水力压裂，并沿垂直于最小主应力的方向近似传播。当热处理温度高于300°C时，由于在井孔附近存在热致损坏区，往往会产生多个带有分支的水力压裂。SPS测试的实验结果表明，水力压裂表面的最大高度差随热处理温度的升高而增加。当热处理温度高于300°C时，水力压裂的曲折度显着增加。此外，对注射压力响应的分析表明，明显的非线性增压，