Cross-hole electrical imaging of a controlled saline tracer injection

L. Slater, A. M. Binley, W. Daily, Richard Johnson

Research output: Contribution to journalArticle

256 Citations (Scopus)

Abstract

Electrical imaging of tracer tests can provide valuable information on the spatial variability of solute transport processes. This concept was investigated by cross-borehole electrical imaging of a controlled release in an experimental tank. A saline tracer (conductivity 8 X 103 ms/m volume 2701) was injected into a tank facility (dimensions 10 X 10 X 3 m) consisting of alternating sand and clay layers. Injection was from 0.3 m below the surface, at a point where maximum interaction between tank structure and tracer transport was expected. Repeated imaging over a two-week period detected non-uniform tracer transport, partly caused by the sand/clay sequence. Tracery accumulation on two clay layers was observed and density-driven spill of tracer over a clay shelf was imaged. An additional unexpected flow pathway, probably caused by complications during array installation, was identified close to an electrode array. Pore water samples obtained following termination of electrical imaging generally supported the observed electrical response, although discrepancies arose when analysing the response of individual pixels. The pixels that make up the electrical images were interpreted as a large number of breakthrough curves. The shape of the pixel breakthrough-recession curve allowed some quantitative interpretation of solute travel time, as well as a qualitative assessment of spatial variability in advective-dispersive transport characteristics across the image plane. Although surface conduction effects associated with the clay layers complicated interpretation, the plotting of pixel breakthroughs was considered a useful step in the hydrological interpretation of the tracer test. The spatial coverage provided by the high density of pixels is the factor that most encourages the approach. (C) 2000 Elsevier Science B.V. All rights reserved.

Original languageEnglish (US)
Pages (from-to)85-102
Number of pages18
JournalJournal of Applied Geophysics
Volume44
Issue number2-3
DOIs
StatePublished - May 2000

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tracers
clays
tracer
injection
pixel
pixels
clay
breakthrough curve
sands
solutes
recession
sand
plotting
curves
boreholes
solute transport
shelves
transport process
travel time
travel

Keywords

  • Pixel-breakthroughs
  • Resistivity
  • Solute transport
  • Tomography

ASJC Scopus subject areas

  • Geophysics

Cite this

Cross-hole electrical imaging of a controlled saline tracer injection. / Slater, L.; Binley, A. M.; Daily, W.; Johnson, Richard.

In: Journal of Applied Geophysics, Vol. 44, No. 2-3, 05.2000, p. 85-102.

Research output: Contribution to journalArticle

Slater, L. ; Binley, A. M. ; Daily, W. ; Johnson, Richard. / Cross-hole electrical imaging of a controlled saline tracer injection. In: Journal of Applied Geophysics. 2000 ; Vol. 44, No. 2-3. pp. 85-102.
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