Phase correction of electromagnetic coupling effects in cross-borehole EIT measurements

Zimmermann

et al. 2016

Improved characterization of subsurface heterogeneity is important to better understand a range of key processes in the hydrologic cycle, such as overland flow, infiltration into the soil, evaporation to the atmosphere, and transpiration by plants. Recently, synthetic modelling studies have shown that information on subsurface heterogeneity can be obtained from the anisotropy in electrical resistivity. The objective of this paper is to experimentally validate the findings of this synthetic modelling study. In order to do so, we developed a new measurement procedure to determine the effective complex electrical resistivity from a set of current injections and voltage measurements on a heterogeneous sample. A synthetic modelling study showed that this new measurement procedure was able to reproduce the results of the previous study that showed how the electrical properties and the correlation length ratio of bimodal distributions of two materials can be obtained from the effective complex electrical resistivity measured in two perpendicular directions. After validation of the new measurement approach, we constructed two bimodal distributions in a 2D measurement cell and applied the newly developed measurement strategy. We were able to estimate the electrical properties, the volume fraction, and the correlation length ratio with good accuracy from the complex resistivity measurements in two directions. The remaining differences were attributed to variations in sediment thickness that occurred during sample preparation. We conclude that anisotropy should not be ignored but embraced when dealing with subsurface heterogeneity and that proper interpretation of anisotropy may actually be used to characterize subsurface heterogeneity.

“…The recent developments of corrections for inductive and capacitive coupling effects in borehole EIT measurements (Zhao et al . , ) now make this possible.…”

Section: Discussionmentioning

confidence: 98%

“…This would also require the availability of field measurements of the complex electrical resistivity in the millihertz to kilohertz frequency range. The recent developments of corrections for inductive and capacitive coupling effects in borehole EIT measurements (Zhao et al 2013(Zhao et al , 2015 now make this possible.…”

Section: Experimental Validationmentioning

confidence: 99%

Using electrical anisotropy for structural characterization of sediments: an experimental validation study

Al-Hazaimay

Zimmermann

et al. 2016

“…However, recent improvements in the correction and inversion of broadband SIP data (Zhao et al . , ; Kelter et al . ) have brought the routine application of broadband SIP measurements in the field a sizeable step closer.…”

Section: Discussionmentioning

confidence: 99%

“…In this case, the measured grain-size distribution would have been included in the variabil-most commercially available systems require an enhancement of the measurement accuracy and corrections to reduce electromagnetic coupling effects for frequencies above 100 Hz. However, recent improvements in the correction and inversion of broadband SIP data (Zhao et al 2013(Zhao et al , 2015Kelter et al 2015) have brought the routine application of broadband SIP measurements in the field a sizeable step closer. In particular, emerging borehole SIP logging tools may be a promising first data source to extend the analysis presented here to field applications.…”

Section: Discussionmentioning

confidence: 99%

Estimation of sediment texture from spectral induced polarisation data using cluster and principal component analysis

Inzoli

Giudici

2016

Spectral induced polarisation data are usually interpreted with simple models in order to derive petrophysical relationships between electrical and sedimentological properties, such as texture, clay content, and permeability. The aim of this work is to explore the value of spectral induced polarisation in addition to conventional direct‐current resistivity measurements for determining textural properties of saturated samples collected from alluvial deposits. For this, an advanced data processing approach that combines cluster and principal component analysis was developed and applied to integral parameters derived from Debye decomposition of spectral induced polarisation data. This data processing procedure allowed identifying groups of samples with a similar spectral induced polarisation response and to derive a characteristic grain‐size distribution for each group of samples. The method to estimate the grain‐size distribution from spectral induced polarisation data was successfully validated using independent sediment samples. The remaining uncertainty in the estimation of sediment texture from spectral induced polarisation data was attributed to the effect of pore size distribution and mineralogy, which were not considered in the present work but can be added in the future within the same conceptual workflow.

“…Dahlin and Zhou 2006;Flores-Orozco et al 2013;Kelter et al 2018). Correction methods for capacitive and inductive coupling effects have also been developed for borehole (Zhao et al 2013(Zhao et al , 2015, and surface FDIP measurements (Zimmermann et al, 2019), but have not yet been transferred to commercially available measurement equipment.…”

Section: F R O M T H E L a B O R A T O R Y T O T H E F I E L D S C A L Ementioning

confidence: 99%

Induced polarization applied to biogeophysics: recent advances and future prospects

Kessouri

Furman

et al. 2019

This paper provides an update on the fast‐evolving field of the induced polarization method applied to biogeophysics. It emphasizes recent advances in the understanding of the induced polarization signals stemming from biological materials and their activity, points out new developments and applications, and identifies existing knowledge gaps. The focus of this review is on the application of induced polarization to study living organisms: soil microorganisms and plants (both roots and stems). We first discuss observed links between the induced polarization signal and microbial cell structure, activity and biofilm formation. We provide an up‐to‐date conceptual model of the electrical behaviour of the microbial cells and biofilms under the influence of an external electrical field. We also review the latest biogeophysical studies, including work on hydrocarbon biodegradation, contaminant sequestration, soil strengthening and peatland characterization. We then elaborate on the induced polarization signature of the plant‐root zone, relying on a conceptual model for the generation of biogeophysical signals from a plant‐root cell. First laboratory experiments show that single roots and root system are highly polarizable. They also present encouraging results for imaging root systems embedded in a medium, and gaining information on the mass density distribution, the structure or the physiological characteristics of root systems. In addition, we highlight the application of induced polarization to characterize wood and tree structures through tomography of the stem. Finally, we discuss up‐ and down‐scaling between laboratory and field studies, as well as joint interpretation of induced polarization and other environmental data. We emphasize the need for intermediate‐scale studies and the benefits of using induced polarization as a time‐lapse monitoring method. We conclude with the promising integration of induced polarization in interdisciplinary mechanistic models to better understand and quantify subsurface biogeochemical processes.