To study in-situ rock stress measurement under different fracture medium, the hydraulic fracturing experiments in lab were carried out using true three axis hydraulic pressure fracture simulating system. The granite specimens with their sizes of 400mmx400mmx400mm were used. In order to study the effect of the slurry density on the stress measurement results, the water with its density 1.0 g/cm3 and the slurry with their densities 1.1~1.4 g/cm3 were used. The continuous pressure-time curves were obtained. The closure pressure points on pressure-time curves were distinguished by using 6 different methods. The closure pressures from 4 methods were consistent with the actual minimum horizontal principal stress (Sh = 5 MPa). Considering the effect of experimental system flexibility, the measured reopening pressure and theoretical reopening pressure were compared. The experimental results showed that the slurry with their densities of 1.1 g/ cm3 and 1.2 g/ cm3 had weak effect on pressure characteristic parameters and the errors were no more than 1 MPa. However, the slurry with densities of 1.3 g/ cm3 and 1.4 g/ cm3 had great effect on pressure characteristic parameters by several times. Our results had an important meaning for the applications of the hydraulic fracturing technology on effect of different fracture media.
In recent years, with the development of economic construction, the boreholes that carried out in-situ rock stress measurement were mostly distributed in the complex geological areas. Many of these boreholes were used different slurry media to prevent the collapse of the borehole. In this case, a new problem was given to the in-situ rock stress measurement technique, that was, whether the stress measurement value was changed or not if the fracture medium was not clear water.
