Fluid injection into sand may initiate fluid-driven fractures. The fluid-sand interaction patterns depend on the injection velocity, fluid viscosity, rheology and stress boundary conditions. However, the extension to non-Newtonian fluids and anisotropic stress conditions, such as in the case of injection of a polymer in the subsurface, is largely unexplored. In this paper, we study the injection of a Newtonian fluid (glycerol aqueous solution) and a shear-thinning fluid (scleroglucan) into a sand-filled Hele-Shaw cell. The experimental results demonstrate complex fracture patterns depending on injection velocity, fluid viscosity, boundary conditions and fluid rheology. The presence of stress-free boundaries causes the fracture opening to be almost perpendicular to the minimum principal stress. The peak injection pressure is also higher compared to the fixed-displacement boundaries. Compared to Newtonian fluid (glycerol), shear thinning polymer (scleroglucan) causes thinner fracture openings and more radial infiltration morphology in sand. The fracturing mechanism in sand is associated with the shear dilation at the tip of fractures and fracture offshoots. This study helps to clarify the basic flow and failure mechanisms of sand when subjected to injection of a non-Newtonian fluid. The insights obtained from these experiments can aid in the prediction of fracture morphology and sweep efficiency for on-site polymer injection.
Hydro-mechanical interactions between fluid flow and solids are common in many industries, such as oil and gas exploration, formation damage caused by particle jamming during oil and gas production (Li et al., 2021a), hydraulic fracturing (Zheng et al., 2020; Zheng and Sharma, 2021, Li et al., 2020), spray coating processes in food processing (Hilton et al., 2013) and tablet production in pharmaceuticals (Hemamanjushree and Tippavajhala, 2020). Different fluid infiltration and fracture opening morphologies caused by the injection of Newtonian fluids affect the fluid injectivity (Li et al., 2021b). However, extensions to non-Newtonian fluids and anisotropic stress conditions, such as in the case of injection of polymers in geological formations, are largely unexplored.