Work

Pore‐Scale Mechanism of Anomalous Saturation Dependence for Induced Polarization: Insights From Desiccation Experiments and Pore‐Network Modeling

Year: 2026

Type: article

Abstract: The complex conductivity method, also known as spectral induced polarization (SIP), is widely used in hydrogeophysical investigations. Power‐law functions with positive exponents between the in‐phase/quadrature components of complex conductivity and water saturation are key petrophysical relationships to interpret field data. However, laboratory and field tests frequently report anomalous observations in which quadrature conductivity (alternatively the normalized chargeability) increases with decreasing saturation. A mechanistic explanation for this phenomenon in terms of electrical double layer polarization theory has been lacking so far. Here, we investigate the pore scale mechanism of this anomalous behavior through laboratory desiccation experiments and numerical simulations. A pore‐network modeling framework that explicitly accounts for water‐solid interfacial effects on complex conductivity is established. The results show that the non‐monotonic dependence of quadrature conductivity on saturation is governed by two mechanisms: (i) the persistence or attenuation of polarization on water‐solid interfaces associated with different pore water configurations (scenarios with or without water film retention) and (ii) preferential drainage of larger pores during desiccation. These findings provide a water‐solid interface‐based physical explanation for the anomalous quadrature conductivity behavior, and offer a mechanistic basis for interpreting geoelectrical data in partially saturated media like soils and rocks.

Source: Journal of Geophysical Research Solid Earth

DOI: 10.1029/2026jb034086

Authors: Siyuan Qiang, Xiaoqing Shi, André Revil, Alexis Maineult