Application of Electrical Resistivity Tomography in Monitoring Recycled Water Injection

This work describes the installation and preliminary measurements of an electrical re¬sistivity tomography (ERT) system to monitor the injection of recycled water into a confined aquifer. The aim is to provide, through time-lapse electrical resistivity tomo¬graphy (ERT) measurements and processing, geoelectrical images of rather increased volumetric sampling around and between the holes and to obtain improved under¬standing of the flow and transport of the injected water. Preliminary measurements involving single-hole ERT measurements were obtained and processed with a 2D inversion algorithm to produce images of the subsurface. Results depict a very good correlation between ERT images and the lithology logs an indication of the reliability of the approach. Those images offer increased resolution and spatial coverage compared to traditional approaches. The entire ERT permanent installation is of low cost, easy to implement and can be used to understand and evaluate the effects of the water injection process.