DNAPL flow and complex electrical resistivity evolution in saturated porous media: A coupled numerical simulation

Area of Science:

• Geophysics
• Environmental Engineering
• Hydrogeology

Background:

• Induced Polarization (IP) is a geophysical technique for subsurface contaminant monitoring.
• Dense Non-Aqueous Phase Liquids (DNAPLs) pose significant environmental challenges.
• Accurate monitoring of DNAPL migration and remediation is crucial.

Purpose of the Study:

• To develop and validate an advanced numerical code for simulating DNAPL flow and IP response.
• To couple multiphase flow modeling with electrical current modeling for enhanced subsurface imaging.
• To assess the accuracy of IP simulations compared to experimental data under varying DNAPL saturation.

Main Methods:

• Developed a 3D numerical model using COMSOL Multiphysics®.
• Coupled multiphase flow and electrical current simulations.
• Validated the model against 2D tank experiments and existing IP/image measurements.

Main Results:

• Simulations showed good agreement with experimental results at low DNAPL saturation, particularly in pumping scenarios.
• Discrepancies were observed between simulated and experimental in-phase resistivity at high DNAPL saturation.
• The coupled IP-multiphase flow model provides a broader spatio-temporal view of contamination.

Conclusions:

• The study presents a preliminary but promising application of coupled IP-multiphase flow for DNAPL detection.
• The model's accuracy is dependent on DNAPL saturation levels.
• Further investigation and extension to larger-scale studies are recommended for improved DNAPL monitoring.