Scale-independent relationship between permeability and resistivity in mated fractures with natural rough surfaces

Geothermal systems consisting of fractures in impermeable rocks are difficult to characterize by in situ methods. In an effort to link characteristics of small-scale and large-scale fractures, this study investigated possible relations between their geophysical parameters. We upscaled the relationship between fracture permeability and formation factor in a laboratory specimen to larger fracture dimensions. Microscopic flow characteristics indicate that this relationship is related to the tortuosity of flow paths. We derived an empirical formula that directly predicts changes in fracture permeability from changes in formation factor. This relation may make it possible to monitor subsurface hydraulic activities through resistivity observations.

Automated summary

By investigating the microscopic flow characteristics of fractures, a relationship between fracture permeability and formation factor was established, potentially allowing for monitoring of subsurface hydraulic activities at a larger scale through resistivity observations.