A Novel Approach to Foam Characterization Using Multi-Frequency Dielectric Technique for Enhanced Oil Recovery

Foam has been used for controlling gas mobility during oil displacement processes in subsurface porous media to mitigate the negative impacts of low gas viscosity, reservoir heterogeneity, and gravity override. Therefore, one potential application of foam is in enhanced oil recovery (EOR) and CO₂ sequestration. However, foams are thermodynamically unstable, and the stability properties need to be evaluated initially before introducing foam into the formations. In this study, we developed a novel approach to characterize foam using a multi-frequency dielectric technique. The dielectric (DI) properties were used to evaluate the foam stability across various surfactant (sodium dodecyl sulfate (SDS)) concentrations (0.1 and 0.3 wt.%) in deionized water (DW) and seawater (SW) using Keysight impedance analyzer. The relative permittivity and electrical conductivity profiles are measured for the foam bulk at a frequency range of 1 MHz to 3 GHz using an open-ended coaxial probe. In parallel, a conventional test is used to study the foam stability over these same ranges of surfactant concentrations, and seawater concentrations. The results confirmed that DI properties measurements provided insights into the foam's bulk properties and interactions. Moreover, the study revealed that water's conductivity increases with frequency due to ion polarization, particularly in the low to intermediate frequency range. When examining different concentrations of foam generated with SDS surfactant in deionized water, it was found that foam exhibited lower permittivity compared to pure deionized water. This is attributed to the interference of surfactant molecules with water's electric field interaction. Furthermore, deionized water demonstrated higher conductivity than foam, which contained more air bubbles, creating discontinuities in the conductive path. As the concentration of SDS increased, a slight increase in conductivity was observed, correlating with increased foam stability. Additionally, the results demonstrated that dielectric properties could effectively evaluate foam stability, showing consistent results with foam stability observed through height measurement over time. This research suggests that dielectric properties could provide an efficient method for assessing foam stability across various foam compositions. Therefore, this will help to improve the understanding of foam stability and set a new standard for in-depth foam research in the petroleum industry, especially for EOR and CO₂ sequestrations.