Flow channeling in a single fracture induced by shear displacement

摘要

The effect on the transport properties of a fracture of a shear displacement u between its complementary surfaces is investigated experimentally and numerically. The shear displacement u induces an anisotropy of the fracture aperture field with a correlation length scaling of |u|, which is significantly larger in the direction perpendicular to u. This reflects the presence of long fluid flow channels perpendicular to the shear displacement, resulting in a higher effective permeability in that direction. Such channels will have a strong influence on the transport characteristics of a fracture, such as, for instance, its thermal exchange area, crucial for geothermal applications. Miscible displacement fronts in shear-displaced fractures obtained experimentally display a self-affine geometry with a characteristic exponent directly related to that of the fracture surfaces. We present a simple model, based on the channeling of the aperture field, which reproduces the front geometry when the mean flow is parallel to the channels created by the shear displacement.