USGS - science for a changing world

USGS Groundwater Information: Hydrogeophysics Branch

*  Home *  Resources [an error occurred while processing this directive] *  Equipment *  Research *  Publications [an error occurred while processing this directive] *  Training *  About *  Contact Us *  Groundwater Information

As part of improvements to the USGS Water Resources Mission Area web presence to better serve you, this site is being sunset.
As some content is migrated to new locations, users will be redirected automatically.
In the interim, these pages are not being updated.
If you have questions, please contact the Hydrogeophysics Branch at

[an error occurred while processing this directive] Internal USGS users should bookmark our new HGB internal home page:

Object-Based Inversion of Crosswell Radar Tomography Data to Monitor Vegetable Oil Injection Experiments

John W. Lane, Jr., U.S. Geological Survey, Storrs, CT
Frederick D. Day-Lewis, Bucknell University, Lewisburg, PA
Roelof J. Versteeg, Idaho National Environmental and Engineering Laboratory, Idaho Falls, ID
Clifton C. Casey, Southern Division NAVFAC, North Charleston, SC


Crosswell radar tomography methods can be used to dynamically image ground-water flow and mass transport associated with tracer tests, hydraulic tests, and natural physical processes. Dynamic imaging can be used to identify preferential flow paths and to help characterize complex aquifer heterogeneity. Unfortunately, because the raypath coverage of the interwell region is limited by the borehole geometry, the tomographic inverse problem is typically underdetermined, and tomograms may contain artifacts such as spurious blurring or streaking that confuse interpretation.

We implement object-based inversion (using a constrained, non-linear, least-squares algorithm) as an alternative to pixel-based inversion approaches that utilize regularization (such as damping or smoothing criteria). Our approach requires pre- and post-injection travel-time data. Parameterization of the image plane comprises a small number of objects rather than a large number of pixels, resulting in an overdetermined problem that reduces the need for prior information. The nature and geometry of the objects are based on hydrologic insight into aquifer characteristics, the nature of the experiment, and the planned use of the geophysical results.

The object-based inversion approach is demonstrated using synthetic and crosswell radar field data acquired during vegetable-oil injection experiments at a site in Fridley, Minnesota. The region where oil has displaced ground water is discretized as a stack of rectangles of variable horizontal extents. The inversion provides the geometry of the affected region and an estimate of the radar slowness change for each rectangle. Applying petrophysical models to these results and porosity from neutron logs, we estimate that the vegetable-oil emulsion saturation in various layers ranges from 60 to 90%. Further work is needed to assess the accuracy of the emulsion saturation estimates.

Using synthetic- and field-data examples, the object-based inversion approach is shown to be an effective strategy for inverting crosswell radar tomography data acquired to monitor the emplacement of vegetable-oil emulsions. A principal advantage of object-based inversion is that it yields images that hydrologists and engineers can easily interpret and use for model calibration.


Download a complete PDF version of this document (765 KB)

Note: Download free Adobe Acrobat Reader to view PDF files at the Adobe web site.
Visit for free tools that allow visually impaired users to read PDF files.

Final copy as submitted to Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP) for publication as: Lane, J.W., Jr., Day-Lewis, F.D., Versteeg, R.J., and Casey, C.C., 2003, Object-based inversion of crosswell radar tomography data to monitor vegetable-oil injection experiment, in Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP), April 6-10, 2003, San Antonio, Texas, Proceedings: Denver, Colorado, Environmental and Engineering Geophysical Society, CD-ROM, 27 p.

USGS Home [an error occurred while processing this directive]USGS Intranet Water [an error occurred while processing this directive]Water Intranet
Climate and Land Use Change Core Science Systems Ecosystems Energy and Minerals Environmental Health Natural Hazards

Accessibility FOIA Privacy Policies and Notices logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Contact the Hydrogeophysics Branch
Page Last Modified: Thursday, 29-Dec-2016 20:03:41 EST