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Inversion of tracer test data using tomographic constraints
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
2006 (English)In: Water resources research, ISSN 0043-1397, Vol. 42, W04410- p.Article in journal (Refereed) Published
Abstract [en]

We have developed a methodology for inverting tracer test data using zonation information obtained from two-dimensional radar tomograms to improve the (typically overly smooth) hydraulic conductivity fields obtained from conventional inversion of tracer test data. The method simultaneously yields two-dimensional estimates of hydraulic conductivity as well as petrophysical relationships that relate hydraulic conductivity to radar velocity; these relationships can be assumed to be stationary throughout the area of investigation or to vary as a function of zonation. Using a synthetic three-dimensional hydraulic conductivity field, we apply the developed inversion methodology and explore the impact of the strength and stationarity of the petrophysical relationship as well as the impact of errors that are often associated with radar data acquisition (such as unknown borehole deviation). We find that adding radar tomographic data to tracer test data improves hydrogeological site characterization, even in the presence of minor radar data errors. The results are contingent on the assumption that a relationship between radar velocity and hydraulic conductivity exists. Therefore the applicability of the proposed method may be limited to field sites where this condition is partially or fully satisfied.

Place, publisher, year, edition, pages
2006. Vol. 42, W04410- p.
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-93412DOI: 10.1029/2004WR003806OAI: oai:DiVA.org:uu-93412DiVA: diva2:166877
Available from: 2005-09-01 Created: 2005-09-01 Last updated: 2009-10-02Bibliographically approved
In thesis
1. Characterization of Hydrogeological Media Using Electromagnetic Geophysics
Open this publication in new window or tab >>Characterization of Hydrogeological Media Using Electromagnetic Geophysics
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Radio magnetotellurics (RMT), crosshole ground penetrating radar (GPR), and crosshole electrical resistance tomography (ERT) were applied in a range of hydrogeological applications where geophysical data could improve hydrogeological characterization.

A profile of RMT data collected over highly resistive granite was used to map subhorizontal fracture zones below 300m depth, as well as a steeply dipping fracture zone, which was also observed on a coinciding seismic reflection profile. One-dimensional inverse modelling and 3D forward modelling with displacement currents included were necessary to test the reliability of features found in the 2D models, where the forward models did not include displacement currents and only lower frequencies were considered.

An inversion code for RMT data was developed and applied to RMT data with azimuthal electrical anisotropy signature collected over a limestone formation. The results indicated that RMT is a faster and more reliable technique for studying electrical anisotropy than are azimuthal resistivity surveys.

A new sequential inversion method to estimate hydraulic conductivity fields using crosshole GPR and tracer test data was applied to 2D synthetic examples. Given careful surveying, the results indicated that regularization of hydrogeological inverse problems using geophysical tomograms might improve models of hydraulic conductivity.

A method to regularize geophysical inverse problems using geostatistical models was developed and applied to crosshole ERT and GPR data collected in unsaturated sandstone. The resulting models were geologically more reasonable than models where the regularization was based on traditional smoothness constraints.

Electromagnetic geophysical techniques provide an inexpensive data source in estimating qualitative hydrogeological models, but hydrogeological data must be incorporated to make quantitative estimation of hydrogeological systems feasible.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 65 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 86
Geophysics, Hydrogeophysics, radio magnetotellurics, ground penetrating radar, electrical resistance tomography, inversion, regularization, geostatistics, electrical anisotropy, fractured rock, Geofysik
National Category
urn:nbn:se:uu:diva-5912 (URN)91-554-6325-8 (ISBN)
Public defence
2005-09-23, Axel Hambergsalen, Geocentrum, Villav. 16, Uppsala, 10:00 (English)
Available from: 2005-09-01 Created: 2005-09-01 Last updated: 2009-03-24Bibliographically approved

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