Time-lapse Electrical Tomography Research Articles

Autonomous time-lapse electrical imaging for real-time management of subsurface systems

Time-lapse electrical imaging has been used for diverse scientific and engineering problems to monitor changes in the subsurface associated with fluid injections, fluid flow, solute transport, phase changes, and other physical and chemical processes. The burgeoning applications of time-lapse electrical imaging underscore its potential to provide valuable, qualitative insight to support development of conceptual models of subsurface frameworks and processes. Advances in electrical geophysical instrumentation and data analysis over the last approximately 25 years allow for long-term, continuous monitoring. We posit that the next step in the evolution of time-lapse electrical imaging is autonomous, real-time monitoring, which has potential to support real-time management decisions and feedback control of subsurface systems. We present (1) a framework for autonomous, real-time electrical imaging and (2) demonstrations of real-time electrical imaging for aquifer remediation monitoring. Two case studies are presented: (1) vadose-zone desiccation and (2) polyphosphate injections to sequester radionuclide contamination.

Resolution of electrical imaging of fluid movement in landfills

This paper investigates the efficacy of time-lapse electrical imaging using surface electrodes to monitor the movement of leachate within a landfill. A laboratory-based study allowed direct comparison between observed physical dewatering and time-lapse electrical imaging data. In combination with a forward modelling study this demonstrated the limitations and advantages of this geophysical technique in terms of its applicability, resolution and complementarity to conventional dewatering monitoring techniques. It also confirmed the nature, likely magnitude and impact of artefacts created by the resistivity inversion process and highlighted the potential for misinterpretation of results. An 18-month study provided field results comparing hydrogeological and imaging data during the dewatering of a real landfill system. Insights gained from the laboratory study and forward modelling exercise greatly enhanced the interpretation of the field data, enabling the method to be applied with greater confidence in the future. The need to combine a forward modelling exercise with any interpretation of resistivity data is clearly demonstrated.