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| Hauptseite > Publikationsdatenbank > TESTING THE POTENTIAL OF GPR-FWI TO DETECT TRACER PLUMES IN TIME-LAPSE MONITORING |
| Hauptseite > Publikationsdatenbank > TESTING THE POTENTIAL OF GPR-FWI TO DETECT TRACER PLUMES IN TIME-LAPSE MONITORING |
| Poster (After Call) | FZJ-2018-04969 |
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2018
Please use a persistent id in citations: http://hdl.handle.net/2128/19642
Abstract: Geophysical methods are increasingly being used in hydrogeological studies, allowing to characterize the structure and the heterogeneity of the subsurface in a noninvasive way. Transport processes could be monitored using these methods when the tracer changes the geophysical properties of the aquifer (e.g. electrical conductivity, permittivity) and when these changes can be resolved in space and time. Ground penetration radar (GPR) measurements processed by the full-waveform inversion (FWI) method allow mapping the subsurface with a decimeter scale resolution. Time-lapse GPR imaging of saline tracer in fractured rock demonstrated the potential to monitor transport processes (e.g. Shakas et al., 2016). In the current research, a time-lapse GPR imaging of a saline tracer test is planned in an alluvial aquifer, to test the potential of GPR to detect transport processes.The experiment will be performed in a sand-gravel aquifer at the Krauthausen test site, nearby Jülich where we will inject a saline tracer into the aquifer through a borehole and transported by natural groundwater flow. Time-lapse GPR data will be acquired in a crosshole setup to monitor the tracer distribution. To optimize the imaging and detection of the tracer plume, a numerical test simulating the field experiment in a hydrogeological model of the aquifer was applied using a flow and transport model and a GPR wave propagation forward model. The numerical experiment simulates the plume spread in time and space, and the signals that are measured with GPR. An appraisal of the spatial resolution of the tracer distribution that can be obtained with GPR is derived from a comparison between the simulated tracer distributions and the tracer distributions obtained after a full waveform inversion of the GPR signals. Preliminary results of the transport simulation show a narrow plume with high salinity gradients at the decimeter scale, which performs the importance of the prediction for optimizing geophysical imaging and interpretation. At the next steps of the simulation, GPR forward modeling followed by FWI will be applied while adjusting the tracer concentrations, radar frequencies, and crosshole locations to optimize imaging of the field experiment.
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