Flow anisotropy in sheared fractures with self-affine surfaces

Abstract

The hydraulic behavior of fractures is important for understanding geothermal reservoirs. Thus experimental and numerical analysis of fractures is important. The roughness of the surfaces of natural fractures has an effect on their permeability. Analytical methods fail to predict this effect in different scales. Here the hydraulic properties of rough fractures are investigated with numerical methods. The fracture model consists of two identical self-affine surfaces, sheared element wise against each other. The heterogeneous aperture is represented by hydraulic conductivity in the numerical model. We use the finite element method in 2D for simulating the fluid flow through the fracture model. Fluid flow is forced with Dirichlet boundary conditions parallel and perpendicular to the shearing direction. The calculated mean flow through all investigated fractures show an anisotropic behavior, dependent on the orientation of the pressure gradient. The flow parallel (perpendicular) to the shearing direction is increased (enhanced). The effect of channeling perpendicular to the direction is the reason for the anisotropy in fluid flow.