Near-wellbore mechanisms of multidirectional fracturing created by injecting shear-thickening fluid

Given that hydraulic fracturing typically generates simple bi-wing fractures aligned with the maximum principal stress, enhancement of permeability is primarily limited to that direction. Generating fractures in directions other than that of the maximum principal stress remains technically challenging. Using shear thickening fluid (STF) in fracturing has been proposed to overcome this limitation because laboratory experiments have demonstrated its unique ability to create multidirectional fractures. However, the underlying mechanisms remain unclear owing to constraints on experimental visualization. In this study, we elucidate the near-wellbore mechanisms of multidirectional fracturing by STF injection using coupled fluid-mechanical discrete element method (DEM) simulations. We implemented a simplified model of the flow of STF incorporating shear-rate-dependent viscosity and relaxation time into our in-house two-dimensional DEM program. We conducted comparative simulations of STF and Newtonian fluid injection under both isotropic and anisotropic stress conditions. Although Newtonian fluid produced conventional bi-wing fractures, STF successfully generated multidirectional cracks in the near-wellbore region in both stress conditions. Detailed analysis revealed the mechanism driving this multidirectional crack generation. When STF flows into the initial cracks, its viscosity drastically increases owing to high shear rates. This thickening effect restricts fluid flow into the crack, sealing it. Consequently, borehole pressure remains elevated, which induces significant tensile stress around the wellbore and allows cracks to initiate in other orientations. Crucially, we confirmed that this crack-sealing mechanism remains consistent even under differential stress. These findings advance the understanding of STF fracturing and validate the potential of this novel technology to further enhance reservoir permeability.