Azimuthal Mapping of Tracer Flow Path Using Optimized Directional In-Hole ERT

Summary This study introduces an optimized methodology for mapping directional contaminant flow paths by integrating rotating surface electrodes with in-hole Electrical Resistivity Tomography (ERT), supported by numerical simulations and validated through field application. Surface electrodes are rotated around a borehole at multiple azimuths while keeping in-hole electrodes stationary. Four electrode configurations—A-BMN, A-MNB, AB-MN, and AM-NB—are assessed using synthetic azimuthal apparent resistivity datasets. Directional sensitivity is evaluated for two scenarios: in-panel anomalies, where surface electrodes align with subsurface anomalies, and off-panel anomalies, where anomalies are opposite the surface electrodes. Arrays with high in-panel and low off-panel sensitivity exhibit reduced symmetrical effects and enhanced directional performance. The results show that symmetrical effects and limited directionality affect the A-BMN and A-MNB arrays, while the AB-MN array displays low accuracy and poor performance. In contrast, the AM-NB array demonstrates superior accuracy, minimal symmetrical effects, and strong directionality. Field tests validate the numerical findings, revealing significant resistivity variations at specific azimuths that align with the orientation of the injection well. Rose diagrams effectively indicate dominant flow paths and contaminant migration directions. This integrated approach offers a reliable, cost-effective solution for detecting preferential flow pathways and advancing subsurface mapping techniques.