Investigating cable effects in spectral induced polarization imaging at the field scale using multicore and coaxial cables

Geophysics ◽  
2020 ◽  
pp. 1-49
Author(s):  
Adrian Flores Orozco ◽  
Lukas Aigner ◽  
Jakob Gallistl
Keyword(s):  
Signal To Noise Ratio ◽  
Electromagnetic Coupling ◽  
Induced Polarization ◽  
Coaxial Cable ◽  
Imaging Method ◽  
Data Sets ◽  
Phase Lag ◽  
Imaging Data ◽  
Measuring Device ◽  
Spectral Induced Polarization

The Spectral Induced Polarization (SIP) method has emerged as a well-suited laboratory technique to characterize hydrogeological and biogeochemical parameters in soil samples. However, field applications of the SIP imaging method are still rare, which can be attributed to the particular care required to minimize the contamination of the data by electromagnetic coupling. To date, field procedures rely on the use of two different cables separating the current and potential dipoles to improve the quality of the SIP readings, although this increases the efforts in the field and might reduce the depth of investigation or the spatial resolution of the data. To overcome these limitations, we investigate here the use of a single coaxial cable, as an alternative to improve data quality and simplify field procedures. We present a thoughtful evaluation of SIP imaging data collected with the same measuring device using a coaxial cable and a combination of multicore cables of different length and manufacturers. Data sets collected with a single coaxial cable reveal a significantly lower number of outliers and high spatial consistency between the phase-lag readings, even for measurements collected with a coaxial cable five times longer than the length of the profile. Furthermore, the data collected with coaxial cables reveal an improved quality for deeper measurements (with lower signal-to-noise ratio) in comparison to data sets collected with separated cables. Our results demonstrate that the use of coaxial cables might permit the collection of SIP readings with high quality and similar field procedures to those used in resistivity surveys.

scholarly journals Spectral Induced Polarization imaging to investigate an ice-rich mountain permafrost site in Switzerland

2021 ◽  
Author(s):  
Theresa Maierhofer ◽  
Christian Hauck ◽  
Christin Hilbich ◽  
Andreas Kemna ◽  
Adrián Flores-Orozco
Keyword(s):  
Electromagnetic Coupling ◽  
Spectral Response ◽  
Induced Polarization ◽  
Swiss Alps ◽  
Spatial Extent ◽  
Data Uncertainty ◽  
Monitoring Site ◽  
Imaging Data ◽  
Spectral Induced Polarization ◽  
Talus Slope

Abstract. Spectral induced polarization (SIP) measurements were collected at the Lapires talus slope, a long-term permafrost monitoring site located in the Western Swiss Alps, to assess the potential of the frequency dependence (within the frequency range of 0.1–225 Hz) of the electrical polarization response of frozen rocks for an improved permafrost characterization. The aim of our investigation was to (a) find a field protocol that provides SIP imaging data sets less affected by electromagnetic coupling and easy to deploy in rough terrains, (b) cover the spatial extent of the local permafrost distribution, and (c) evaluate the potential of the spectral data to discriminate between different substrates and spatial variations in the volumetric ice content within the talus slope. To qualitatively assess data uncertainty, we analyze the misfit between normal and reciprocal (N&R) measurements collected for all profiles and frequencies. A comparison between different cable setups reveals the lowest N&R misfits for coaxial cables and the possibility to collect high-quality SIP data in the range between 0.1–75 Hz. We observe an overall smaller spatial extent of the ice-rich permafrost body compared to its assumed distribution from previous studies. Our results further suggest that SIP data help to improve the discrimination between ice-rich permafrost and unfrozen bedrock in ambiguous cases based on their characteristic spectral behavior, with ice-rich areas showing a stronger polarization towards higher frequencies in agreement with the well-known spectral response of ice.

Inversion of 2D spectral induced polarization imaging data

2006 ◽  
Vol 54 (3) ◽  
pp. 287-301 ◽  
Author(s):  
M.H. Loke ◽  
J.E. Chambers ◽  
R.D. Ogilvy
Keyword(s):  
Induced Polarization ◽  
Imaging Data ◽  
Polarization Imaging ◽  
Spectral Induced Polarization

Cable arrangement to reduce electromagnetic coupling effects in spectral-induced polarization studies

Geophysics ◽  
2014 ◽  
Vol 79 (2) ◽  
pp. A1-A5 ◽  
Author(s):  
Myriam Schmutz ◽  
Ahmad Ghorbani ◽  
Pierre Vaudelet ◽  
Amélie Blondel
Keyword(s):  
Coupling Effect ◽  
Electromagnetic Coupling ◽  
Induced Polarization ◽  
Electrode Spacing ◽  
Coupling Effects ◽  
Array Type ◽  
Spectral Induced Polarization ◽  
Computer Codes ◽  
Lateral Offset ◽  
Phase Angles

Spectral-induced polarization (SIP) is widely used for environmental and engineering geophysical prospecting and hydrogeophysics, but one major limitation concerns the electromagnetic (EM) coupling effect. The phase angles related to EM coupling may increase even at frequencies as low as 1 Hz, depending on the ground resistivity, the array type, and the geometry. Most efforts to understand and quantify the EM coupling problem (e.g., theory and computer codes) have been developed for dipole-dipole arrays. However, we used a Schlumberger array to acquire SIP data. We found that with this array, the use of an appropriate cable arrangement during data acquisition can reduce EM coupling effects in the same proportion as for the use of a dipole-dipole array, which is the pure response of the studied earth. To measure the influence of the cable layout, four cable configurations with the same electrode spacing were compared for modeling and experimental data. We discovered that the classical DC inline array was the worst one. As soon as the cables were arranged in another shape (triangle or rectangle), the coupling effect decreased significantly. The best configuration we checked was the rectangular one with an acquisition unit located at a lateral offset of 100 m from the electrode line, even if there was still some difference between the modeled and measured data.

Induced polarization response of porous media with metallic particles — Part 5: Influence of the background polarization

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. E77-E96 ◽  
Author(s):  
André Revil ◽  
Michael F. Sleevi ◽  
Deqiang Mao
Keyword(s):  
Porous Materials ◽  
Tap Water ◽  
Current Model ◽  
Clay Content ◽  
Peak Frequency ◽  
Exchange Capacity ◽  
Induced Polarization ◽  
Data Sets ◽  
Phase Lag ◽  
Polarization Spectra

Very often, ore bodies are found in altered porous materials that are rich in clay minerals. These altered rocks are in turn characterized by a relatively high normalized chargeability (product of the chargeability by the high frequency conductivity) or electrical quadrature conductivity with respect to clay-free materials. We have performed 36 experiments in which dispersed pyrite grains were mixed with a background host material composed of some pore water (NaCl, [Formula: see text] at 25°C or tap water), Na-exchanged bentonite, and silica grains. The induced polarization spectra were obtained in the frequency range of 1 mHz to 45 kHz at room temperature ([Formula: see text]). The spectra of the background porous materials alone (i.e., without pyrite) were also measured. The normalized chargeability and the quadrature conductivity of the sand-clay mixtures are consistent with available theoretical relationships. These new data complete previous data sets showing a clear relationship among the normalized chargeability, quadrature conductivity, surface conductivity, and cation exchange capacity. Bentonite is characterized by very high quadrature and surface conductivities. The normalized chargeability and the quadrature conductivity of the sand-clay mixtures (no pyrite) increase with the clay content. In the presence of pyrite, the chargeability and the phase lag depend primarily on the volume content of pyrite in a predictable way. The Cole-Cole exponent, characterizing the particle size distribution of the pyrite grains, is independent of the clay content. Still, in the presence of pyrite, the magnitude of the phase peak and the phase peak frequency depend on the clay content in a way that is not explained by the current model. We have observed that the Cole-Cole relaxation time, in the presence of pyrite, is inversely proportional to the conductivity of the background material.

scholarly journals ANALYSIS OF COMPLEX APPARENT RESISTIVITY DATA CONJUGATING SPECTRAL INDUCED POLARIZATION AND ELECTROMAGNETIC COUPLING

2018 ◽  
Vol 36 (3) ◽  
pp. 1
Author(s):  
Taíla Crístia Souza Sant’Ana ◽  
Edson Emanoel Starteri Sampaio
Keyword(s):  
Apparent Resistivity ◽  
Mineral Exploration ◽  
Electromagnetic Coupling ◽  
Synthetic Data ◽  
Polarization Characteristic ◽  
Induced Polarization ◽  
Forward Modelling ◽  
New Approach ◽  
Spectral Induced Polarization ◽  
Geological Information

ABSTRACT. The induced polarization characteristic is to provide geophysical and geological information via geoelectric parameters, making possible mineral discrimination in the scope of mineral exploration. Although represents one of the main noises in measurements of this method, electromagnetic coupling between current and potential electrodes also contributes to the understanding of the geological scenario. Thus, the most appropriate way to deal with such data is an integrated study of these two phenomena, taking into account their particularities. Forward modelling and Gauss-Newton inversion of the mutual impedance in the frequency domain provide the analysis of the complex apparent resistivity considering both spectral induced polarization and electromagnetic coupling for homogeneous and one-dimensional, non-polarizable and polarizable Earth models. Besides synthetic data, this new approach was applied to data from the Copper District of Vale do Curaçá, Bahia, Brazil. The results reveal the ability of the method to distinguish between induction, dominant at the highest frequencies, and induced polarization, which varies with depth and frequency. It also may constitute a basis for mineral discrimination with the analysis of analogous circuit parameters, a fundamental tool in the search for metallic targets in mineral exploration.Keywords: Forward Modelling, Geophysical Inversion, Electromagnetic Method, Mineral Exploration.RESUMO. A polarização induzida espectral se destaca por fornecer diversas informações geofísico-geológicas através dos parâmetros geoelétricos, viabilizando a discriminação mineral no âmbito da exploração mineral. Embora constitua um dos principais ruídos nas medidas desse método, o acoplamento eletromagnético entre eletrodos de corrente e potencial também auxilia na compreensão do cenário geológico. Dessa forma, a maneira mais adequada de lidar com tais dados espectrais é o estudo integrado desses dois fenômenos, levando em conta suas particularidades. A modelagem direta e a inversão Gauss-Newton da impedância elétrica mútua no domínio da frequência proporcionam a análise da resistividade complexa aparente considerando tanto a polarização induzida espectral como o acoplamento eletromagnético para modelos de terra homogênea e uni-dimensional, polarizável e não-polarizável. Além do dado sintético, essa nova abordagem foi aplicada a dados reais do Distrito Cuprífero do Vale do Curaçá, Bahia, Brasil. Os resultados revelam a capacidade do método em distinguir o efeito indutivo, dominante nas mais altas frequências, e a variação da polarização induzida com a profundidade e frequência. Isso contitui um estudo base para a discriminação mineral por meio da análise de parâmetros de circuitos análogos, uma ferramenta fundamental na investigação de alvos em exploração mineral.Palavras-chave: Modelagem direta, Inversão Geofísica, Método Eletromagnético, Exploração Mineral. 1Universidade

scholarly journals Broadband Spectral Induced Polarization for the detection of Permafrost and an approach to ice content estimation – A Case study from Yakutia, Russia

2021 ◽  
Author(s):  
Jan Mudler ◽  
Andreas Hördt ◽  
Dennis Kreith ◽  
Kirill Bazhin ◽  
Lyudmila Lebedeva ◽  
...  
Keyword(s):  
Induced Polarization ◽  
Parameter Distribution ◽  
Physical Parameters ◽  
Frequency Range ◽  
Field Scale ◽  
Frequency Dependent ◽  
Multidimensional Distribution ◽  
Measuring Device ◽  
Spectral Induced Polarization ◽  
Ice Content

Abstract. The reliable detection of subsurface ice using non-destructive geophysical methods is an important objective in permafrost research. Furthermore, the ice content of the frozen ground is an essential parameter for further interpretation, for example in terms of risk analysis, e.g. for the description of permafrost carbon feedback by thawing processes. The High-Frequency Induced Polarization method (HFIP) enables the measurement of the frequency dependent electrical signal of the subsurface. In contrast to the well-established Electrical Resistivity Tomography (ERT), the usage of the full spectral information provides additional physical parameters of the ground. As the electrical properties of ice exhibit a strong characteristic behaviour in the frequency range between 100 Hz and 100 kHz, HFIP is in principle suitable to estimate ice content. Here, we present methodological advancements of the HFIP method and suggest an explicit procedure for ice content estimation. A new measuring device, the Chameleon-II (Radic Research), was used for the first time. It was designed for the application of Spectral Induced Polarization over a wide frequency range and is usable under challenging conditions, for example in field sites under periglacial influence and the presence of permafrost. Amongst other improvements, compared to a previous generation, the new system is equipped with longer cables and larger power, such that we can now achieve larger penetration depths up to 10 m. Moreover, it is equipped with technology to reduce electromagnetic coupling effects which can distort the desired subsurface signal. The second development is a method to estimate ice content quantitatively from five Cole-Cole parameters obtained from spectral two-dimensional inversion results. The method is based on a description of the subsurface as a mixture of two components (matrix and ice) and uses a previously suggested relationship between frequency-dependent electrical permittivity and ice content. Measurements on a permafrost site near Yakutsk, Russia, were carried out to test the entire procedure under real conditions at the field scale. We demonstrate that the spectral signal of ice can clearly be identified even in the raw data, and show that the spectral 2-D inversion algorithm is suitable to obtain the multidimensional distribution of electrical parameters. The parameter distribution and the estimated ice content agree reasonably well with previous knowledge of the field site from borehole and geophysical investigations. We conclude that the method is able to provide quantitative ice content estimates, and that relationships that have been tested in the laboratory may be applied at the field scale.

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