Capability of cross-hole electrical configurations for monitoring rapid plume migration experiments

• We evaluate the cross-hole resistivity configurations for real-time monitoring.
• The anomaly detection and symmetry on the sensitivity pattern is analyzed.
• An easy way to reduce acquisition time and amount of data for monitoring is presented.
• This data reduction preserves the configurations capability and resolution.

Cross-hole electrical resistivity tomography is a useful tool in geotechnical, hydrogeological or fluid/gas plume migration studies. It allows better characterization of deep subsurface structures and monitoring of the involved processes. However, due to the large amount of possible four-electrode combinations between boreholes, the choice of the most efficient ones for rapid plume migration experiments (real-time monitoring), becomes a challenge. In this work, a numerical simulation to assess the capabilities and constraints of the most common cross-hole configurations for real-time monitoring is presented. Four-electrode configurations, sensitivity, dependence on the body location and amount of data were taken into account. The analysis of anomaly detection and the symmetry of the sensitivity pattern of cross-hole configurations allowed significant reduction of the amount of data and maintaining the maximum potential resolution of each configuration for real-time monitoring. The obtained results also highlighted the benefit of using the cross-hole AB–MN configuration (with both current – or potential – electrodes located in the same borehole) combined with other configurations with complementary sensitivity pattern.