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Dnapl Detection Sensitivity Of A High-Resolution Directional Borehole RadarNormal access

Authors: Craig W. Moulton and David L. Wright
Event name: 16th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
Session: Borehole Geophysics
Publication date: 06 April 2003
Organisations: EEGS
Language: English
Info: Extended abstract, PDF ( 1.3Mb )

The U.S. Geological Survey has developed a directional borehole radar system (DBOR) for
high-resolution imaging close to borehole wells. We have conducted physical and numerical modeling
to assess the ability of this radar to detect and map the location of dense non-aqueous phase liquids
(DNAPLs) near a borehole.
Physical modeling was conducted in a water-saturated silica sand-filled tank. Model targets
included silica sand saturated with mineral oil and a paraffin cylinder. The oil-sand mixtures were
sealed in plastic bags of the desired shape and placed in the sand at various distances and orientations
relative to the borehole. Physical modeling showed that the paraffin and oil-sand rectangular targets and
the thick wedge against the borehole imaged well. The thick and thin wedges away from the borehole
were more difficult to discern.
Finite-difference time-domain (FDTD) numerical modeling was done for some geometries and
electrical properties that were physically modeled and will also include additional cases in the future.
Results indicate that the radar system will be able to detect and map the location of small amounts of
DNAPL in a controlled spill experiment to be conducted by the U.S. Environmental Protection Agency.

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