Three dimensional time lapse monitoring of a saline tracer in an experimental tank

We present a 4D geoelectrical time lapse experiment simulating the movement of olive oil mill wastes into a sequence of impermeable (fine sand) to permeable (medium sand) formations. Prior to the full experimental set-up a smaller scale test took place in a small experimental aquarium in order to simulate the movement of the saline tracer. The actual experiment involved a large (one cub. meter) tank instrumented with electrodes deployed in six vertical and two horizontal boreholes. A saline tracer was injected in to the saturated permeable medium and its movement was monitored by collecting 21 timelapse full 3D ERT data sets. Data were processed using a 4D inversion algorithm and the time lapse geoelectrical images captured the red dye tracer movement. The laboratory experiment confirmed that the 4D approach provided improved time-lapse monitoring of changes in a real system. The above model will be used to extract hydrogeological parameters and create a model of the saline tracer flow and evaluate the applicability of ERT monitoring in this context.