부산대학교 도서관

To clarify the characteristics of induced-injection slip under high temperature and the influence on permeability, injection-induced slip experiment using cylindrical specimen with a 45 ° tilted tensile fracture was conducted under the condition 200 - 500 °C. As a result, two types of slips, initial slip and stable slip, were observed under all temperature conditions. The initial slip velocity was constant under brittle conditions and tended to decrease with increasing temperature under ductile conditions. On the other hand, the stable slip velocity decreased continuously with increasing temperature. In the case of granite, the friction coefficient at the start of stable slip tended to increase at temperatures over 400 °C. This suggests that in the ductile condition, the contact area of the fracture surface increases with increasing temperature and the fracture becomes less likely to slip. Additionally, the slip experiments using basalts suggest that under the brittle condition, slips may occur by the same mechanism even if the rock types are different. The permeability after the slip experiment was sufficiently large under the brittle condition but decreased rapidly near the brittle-ductile transition condition and decreased to half at 500 °C. Under ductile conditions, the improvement of permeability due to slip cannot be expected, but the permeability did not decrease to one order of magnitude. Therefore, it is thought that if three-dimensionally distributed fractures with sufficient permeability can be generated in advance, permeability that can perform well as a geothermal reservoir can be maintained. In addition, it was found that the initial slip velocity depends more on the stress field than on the temperature. However, the initial slip velocity under the conditions of 400 °C and normal stress of 55 MPa was a sufficiently small value of 2 μm/s. Also, even if a slip occurrs, it shifts to a stable slip with a lower slip velocity, and it is considered that seismic slip is unlikely to occur under high temperature and high pressure environment.