Study of the mechanism of multidirectional fracturing of rock using shear-thickening viscous fluid

The direction of fractures nucleated by hydraulic fracturing is determined with in situ stress and is generally unidirectional. However, our previous experimental study demonstrated that using shear thickening fluid (STF) on granite samples resulted in multidirectional fractures. This fracturing might be able to improve permeability around the borehole much further. In this study, we investigated whether there is a difference in the fracturing formation at STF fracturing depending on the stress conditions and tried to clarify the conditions of multidirectional fracturing with STF. We conducted the STF fracturing experiment under various uniaxial and biaxial stress conditions. From the results, multidirectional fractures were more likely to be nucleated when the vertical stress was high under uniaxial conditions. Also, when the vertical stress was low, unidirectional fractures were nucleated. The difference was caused by the effect of STF in fracture plugging. Under biaxial conditions, the range of directions of nucleated fractures was wider when the differential stress was low and more restricted when differential stress was high. This was because fractures opening and accompanied STF solidification effect was suppressed depending on the magnitude of the hoop stress.