Investigating Permeability Anisotropy in a Rough Fracture: A Novel Shear-Flow Setup

The coupled flow, transport, and hydro-chemo-mechanical processes in fractured porous media have great relevance for numerous applications including underground water management, hydrocarbon recovery, CO₂ sequestration, and geological waste disposal. We developed a novel experimental setup designed to investigate these coupled processes. The setup uses fully matched transparent rectangular fracture blocks. These blocks are created by molding a granite fracture surface with resin. The design of the experimental setup provides controlled shear and normal stresses with simultaneous measurement of the resulting stresses and displacement in both the normal and shear directions. The fluid is injected from the center and flows radially toward the outputs.  There are nine discrete outlets per side to provide high-resolution measurements of the redistribution of flow and permeability anisotropy at various flow and stress conditions. Moreover, we utilize high-resolution imaging and fluorescent tracers to visualize real-time flow.

The results of shear-flow experiments showed that shear displacement enhances the permeability in the direction perpendicular to the applied shear stress. This anisotropic behavior results from the development of preferred flow paths due to the dilation and changes in the geometry of fractures caused by shear. This result was supported by high-resolution fluorescent tracer imaging, which likewise showed the changes in flow paths during shear-flow tests.

This experimental setup enables us to study coupled hydraulic, mechanical, and chemical processes, with precise evaluation of permeability anisotropy under a wide range of conditions. In the next step, we will utilize this setup for two-phase flow studies, as it has often been a challenging complexity in fractured porous media.