Study of fracture initiation and propagation in HDR based on true triaxial experiment in high temperature

Abstract

At present, the main way to exploit hot dry rock (HDR) is to inject the low-temperature working fluid into the high-temperature formation, and then extract the geothermal resources after heating. Hydraulic fracturing of HDR reservoirs is an important technique to increase geothermal production. Compared with normal temperature reservoir, temperature is an important factor that can not be ignored in the fracturing of HDR reservoir, and the complex multi-field coupling caused by temperature change is difficult to be realized by numerical modeling method at present. In this paper, the effects of temperature, in-situ stress and fracturing fluid injection rate during fracturing were investigated with the help of custom-built, heated, large-scale true triaxial hydraulic fracturing equipment. The results show that temperature influences fracture pressure and brittleness of rock. The higher the temperature, the lower the fracture pressure and the weaker the brittleness. The influence of in-situ stress and fluid injection velocity on HDR reservoir is similar to the influence of normal temperature formation fracturing. The experience and method of normal temperature reservoir fracturing design can be referred to in the design of HDR reservoir fracturing.