| Abstract:The primary method for producing hot dry rock (HDR), a clean and renewable energy source, is enhanced geothermal systems (EGS). Geothermal drilling technology is required for the construction of both production and injection wells in the EGS project. The occurrence of formation rupture and well wall collapse during the high temperature and high pressure drilling process are significant issues that must be addressed when drilling dry heat rock. Therefore, to increase the wellbore's stability and boost its safety throughout the geothermal mining process, less rock rupture is likely to occur. This paper uses RFPA numerical simulation software to study the crack extension of wellbore granite under cold impact during dry heat rock mining. The findings indicate that the tensile stress on the rock surface increases to a peak during the wellbore model's cold impact process and then gradually lowers as the cold impact period increases. There are three general stages to the crack extension: pre, medium, and late. A ring-shaped tensile stress zone forms around the wellbore during the pre-cold shock phase, and uniformly sized small fractures start to show up.During the intermediate phase of cold shock, as time passes, the tensile stress zone progressively extends to the wellbore's edge, and the cracks grow outward in tandem with it. The magnitude of the tensile stress steadily shrinks in the late stage of cold shock until it is less than the estimated tensile strength, and the rate of crack expansion slows down until it eventually stops spreading. The temperature, surrounding pressure, and well diameter all have a substantial impact on the damage injury effect of the wellbore surrounding rock during cold impact. Specifically, the temperature encourages the expansion of cold-impact cracks, while the surrounding pressure inhibits their growth. |
