Permeability evaluation for artificial single rock fracture according to geometric aperture variation using electrical resistivity

Abstract

A convenient approach was proposed by which to evaluate and monitor the permeability of a rock fracture by verifying the quantitative correlation between the electrical resistivity and permeability at laboratory scale. For this purpose, an electrical resistivity measurement system was applied to the laboratory experiments using artificial cells with the shape of a single rock fracture. Sixty experiments were conducted using rock fractures according to the geometry, aperture sizes, wavelengths, and roughness amplitudes. The overall negative relationship between the normalized electrical resistivity values and the aperture sizes directly linked with the permeability, was well fitted by the power-law function with a large determination coefficient (≈0.86). The effects of wavelength and roughness amplitude of the rock fracture on the electrical resistivity were also analyzed. Results showed that the electrical resistivity was slightly increased with decreasing wavelength and increasing roughness amplitude. An empirical model for evaluating the permeability of a rock fracture was proposed based on the experimental data. In the field, if the electrical resistivity of pore groundwater could be measured in advance, this empirical model could be applied effectively for simple, quick monitoring of the fracture permeability. Although uncertainty may be associated with the permeability estimation due to the limited control parameters considered in this research, this electrical resistivity approach could be helpful to monitor the rock permeability in deep underground facilities such as those used for radioactive waste repositories or forms of energy storage.

Keywords

• Permeability
• Rock fracture
• Electrical resistivity
• Fracture geometry
• Long-term monitoring