Characterization and Monitoring of Porous Media with Electrical Imaging: A Review

Electrical geophysical imaging is a widely used noninvasive technology for visualizing porous media at scales larger than individual pores. Originally developed for medical applications, the technology has been applied to investigate flow and transport properties/processes in a wide range of fields including earth sciences, civil and environmental engineering, agricultural sciences and biology. Conventional electrical imaging measures electrical conduction processes occurring through the fluids filling the interconnected pores and within the electrical double layer at the solid-fluid interface. Complex electrical imaging, an extension of the methodology, also measures electrical polarization processes within the electric double layer and in the presence of metals. Electrical imaging has been used to determine the spatial distribution of physical properties controlling flow/transport in porous media, image fluid dynamics, observe solute transport phenomena and capture matrix transformations. The method has been applied to investigate porous media processes in soils, rocks, concrete, engineered barriers, wastewater filters and living trees. Advances in the technology will result from (1) improving the understanding of the relationship of complex conductivity measurements to more processes occurring in porous media and (2) developing new instrumentation that will support longer-term autonomous electrical monitoring.