Seasonal variation of moisture content in unsaturated sandstone inferred from borehole radar and resistivity profiles

Binley, Andrew; Winship, Peter; West, L. J.; Pokar, Magdeline; Middleton, Roy

doi:10.1016/s0022-1694(02)00147-6

Cited by 175 publications

(133 citation statements)

References 14 publications

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“…The recorded EM signal provides information on the electrical permittivity and the electrical conductivity of the investigated formation, that can be related to velocity and the attenuation of the EM wave, respectively (Annan, 2005). To date, published field studies using crosshole GPR only include sediments with low electrical conductivity, e.g., unconsolidated sands (Cassiani et al, 2006;Irving et al, 2007;Haarder et al, 2015;Looms et al, 2008;Klotzsche et al, 2010;Gueting et al, 2015), sandstone (Binley et al, 2002), and chalk (Keskinen et al, 2017). In general, clayey environments have been avoided as the attenuation of the EM signal reduces the signal strength and thereby the possible distance between boreholes.…”

Section: Introductionmentioning

confidence: 99%

Mapping sand layers in clayey till using crosshole ground-penetrating radar

et al. 2018

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Fluid transport through clayey tills governs the quantity and quality of groundwater resources in the Northern hemisphere. This transport is often controlled by a three-dimensional network of macropores (biopores, fractures and sand lenses) within the clayey till. At present, a non-destructive technique that can map and characterize the sand-lens-network does not exist, and full excavation or extensive drilling is therefore the only solution. Acquisition and modeling of crosshole ground penetrating radar (GPR) may provide the answer to this problem. We collected one-and two-dimensional crosshole GPR data at a field site in Denmark between four 8-m-deep boreholes with horizontal distances varying between 2.64-5.05 m. We show that the depth, thickness, and tilt of a coherent sand layer within the clayey till (approximately 0.4-0.6 m thick) as well as the underlying sand formation can be mapped accurately using the GPR data.We identified the sand efficiently as a highly resistive section with high electromagnetic wave velocities, while the clayey till was conductive with lower electromagnetic wave velocities. We found that the exact location of the sand occurrences was better delineated by the increase in amplitude than the increase in electromagnetic wave velocity. We believe that crosshole GPR may contribute significantly to groundwater protection and contaminant remediation initiatives.

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Section: Introductionmentioning

confidence: 99%

Mapping sand layers in clayey till using crosshole ground-penetrating radar

et al. 2018

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“…Among the available geophysical techniques, time-lapse electrical resistivity tomography (ERT) is one of the most popular methods . Given its sensitivity to numerous soil/rock properties, ERT has been applied in various contexts, such as salt-tracer experiments (Doetsch et al, 2012b;Robert et al, 2012), dynamics of infiltration and saturation in the vadose zone (Binley et al, 2002;Koestel et al, 2008), monitoring of permafrost (Krautblatter et al, 2010;Supper et al, 2014), interaction between surface and groundwater (Coscia et al, 2011), and more recently to CO 2 sequestration (Carrigan et al, 2013) and heat-tracing experiments Arato et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Covariance-constrained difference inversion of time-lapse electrical resistivity tomography data

2016

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Hydrogeophysics has become a major field of research in the past two decades, and time-lapse electrical resistivity tomography (ERT) is one of the most popular techniques to monitor passive and active processes in shallow subsurface reservoirs. Time-lapse inversion schemes have been developed to refine inversion results, but they mostly still rely on a spatial regularization procedure based on the standard smoothness constraint. We have applied a covariance-based regularization operator to the time-lapse ERT inverse problem. We first evaluated the method for surface and crosshole ERT with two synthetic cases and compared the results with the smoothness-constrained inversion (SCI). These tests showed that the covariance-constrained inversion (CCI) better images the target in terms of shape and amplitude. Although more important in low-sensitivity zones, we have observed improvements everywhere in the tomograms. Those synthetic examples also show that an error made in the range or in the type of the variogram model had a limited impact on the resulting image, which still remained better than SCI. We then applied the method to cross-borehole ERT field data from a heat-tracing experiment, in which the comparison with direct measurements showed a strong improvement of the breakthrough curves retrieved from ERT. This method could be extended to the time dimension, which would allow the use of CCI in 4D inversion schemes.

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“…Quantitative interpretation remains indeed difficult without additional information, generally in the form of a few additional in situ measurements or/and the use of additional geophysical methods (for instance GPR or induced polarization). Electrical resistivity tomography (ERT) has proven its efficiency to image and/or monitor spatial phenomena [43] such as salt water intrusions [44,45], variations in moisture content (e.g., [46,47]), biodegradation of hydrocarbons (e.g., [48,49]) and salt tracer experiments (e.g., [50,51] and references therein). An in-depth review of electrical properties of rocks can be found in Schön [52] or Revil et al [53], whereas a description of electrical methods can be found in Binley and Kemna [54].…”

Section: Electrical Resistivity Tomographymentioning

confidence: 99%

Geophysical Methods for Monitoring Temperature Changes in Shallow Low Enthalpy Geothermal Systems

Hermans

Nguyen

Robert³

et al. 2014

Energies

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Low enthalpy geothermal systems exploited with ground source heat pumps or groundwater heat pumps present many advantages within the context of sustainable energy use. Designing, monitoring and controlling such systems requires the measurement of spatially distributed temperature fields and the knowledge of the parameters governing groundwater flow (permeability and specific storage) and heat transport (thermal conductivity and volumetric thermal capacity). Such data are often scarce or not available. In recent years, the ability of electrical resistivity tomography (ERT), self-potential method (SP) and distributed temperature sensing (DTS) to monitor spatially and temporally temperature changes in the subsurface has been investigated. We review the recent advances in using these three methods for this type of shallow applications. A special focus is made regarding the petrophysical relationships and on underlying assumptions generally needed for a quantitative interpretation of these geophysical data. We show that those geophysical methods are mature to be used within the context of temperature monitoring and that a combination of them may be the best choice regarding control and validation issues. OPEN ACCESSEnergies 2014, 7 5084

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Seasonal variation of moisture content in unsaturated sandstone inferred from borehole radar and resistivity profiles

Cited by 175 publications

References 14 publications

Mapping sand layers in clayey till using crosshole ground-penetrating radar

Mapping sand layers in clayey till using crosshole ground-penetrating radar

Covariance-constrained difference inversion of time-lapse electrical resistivity tomography data

Geophysical Methods for Monitoring Temperature Changes in Shallow Low Enthalpy Geothermal Systems

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