Stress-controlled fluid flow in fractures at the site of a potential nuclear waste repository, Finland

The relationship between present-day stress state and fluid flow within fractures in crystalline bedrock is investigated in the light of a comprehensive fracture database consisting of 38,703 fracture observations made during investigations at the site of a planned high-level nuclear waste repository in Finland. By combining fracture orientation data with detailed stress and fluid flow measurements, we observe that the orientations of conductive fractures display characteristic patterns attributed to the effect of the present-day triaxial stress state and that the highest transmissivities are associated with fractures having the lowest normal tractions. Our findings indicate that contemporary stress data combined with slip and dilation tendency analysis can be used in predicting the orientations and relative transmissivity values of conductive fractures.