A Novel Experimental Set-up for Simultaneous Acquisitions of Spectral Induced Polarization and X-ray µCT Data in 3D Porous Media

Understanding multi-phase pore-scale dynamics and their impact on bulk electrical properties is essential when monitoring reactive flow and transport processes  in many applications. This study introduces a novel experimental setup combining simultaneously Spectral Induced Polarization (SIP) acquisition with X-ray micro-computed tomography (µCT) for real-time monitoring. This innovative approach enables spectroscopic measurements, from mHz to kHz, to be directly correlated with dynamic imaging of pore-scale fluid and grain distributions. The setup features a custom-designed flow cell capable of operating under controlled pressure (up to 120 bars) and temperature (up to 100°C) allowing for real-time monitoring of dynamic petrophysical processes such as multi-phase flow, reactive transport, and mineral precipitation and/or dissolution.

In this contribution, we validate the experimental set-up under variable saturation conditions. Using a medium-grained sand sample,  we conducted a series of eight experiments transitioning from dry to fully saturated states, followed by three progressive partial desaturations steps via nitrogen gas injection and subsequent three progressive re-saturations. µCT scans were performed with 2001 projections and 17.21 µm voxel size resolution for each image. SIP data, spanning the 10 mHz – 45 kHz frequency range, were integrated with µCT-derived pore network models to analyze resistivity variations as functions of pore size, connectivity, and tortuosity.

Our results reveal that simultaneous Spectral Induced Polarization and X-ray micro-computed tomography measurements capture transient fluid redistribution processes, providing enhanced interpretability of bulk electrical responses. We observed significant hysteresis in Spectral Induced Polarization data during drainage and re-saturation cycles, linked to pore-scale fluid trapping and structural changes. Furthermore, resistivity predictions from the pore network model aligned closely with experimental data, validating the integration's robustness.

This novel experimental set-up lay the groundwork to the study of coupled structural and electrical dynamics in porous media, offering valuable insights into pressure and temperature dependant multi-phase subsurface processes including ones with mineral reactivity. By bridging the observation gap between pore-scale processes and bulk geophysical responses in 3D, this approach sets a new standard for experimental petrophysics.