Effects of Temperature and Confining Stress on the Hydraulic Fracturing Behavior of Granite: An Experimental and Numerical Study

Abstract

Hydraulic fracturing technology has been widely applied to the exploitation of hot dry rock (HDR), and the understanding of hydraulic fracturing behavior of rocks is of great significance for improving the permeability of reservoirs. Laboratory tests of hydraulic fracturing based on real granite specimens and the corresponding numerical simulations were carried out to investigate the fracturing pattern of granite, the evolution characteristics of microcracks, and the effects of temperature and confining stress on fracturing pressure. The results indicate that the fracturing pressure increases continuously with the confining stress and decreases significantly with increasing temperature and that the granite temperature is the primary factor controlling the hydraulic fracturing behavior of granite under the conditions of temperature (20–100 ℃) and confining stress (0–1.5\xa0MPa). The granite specimen shows a tensile failure mode, and some short-branch cracks appear at the outer edge of the specimen or around the wellbore. The number of microcracks shows an increasing trend during hydraulic fracturing, and the fracturing process can be divided into three stages according to the growth rate of microcracks.