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- Kemna, Andreas, et al.
(author)
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An overview of the spectral induced polarization method for near-surface applications
- 2012
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In: Near Surface Geophysics. - : Wiley. - 1873-0604 .- 1569-4445. ; 10:6, s. 453-468
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Journal article (peer-reviewed)abstract
- Over the last 15 years significant advancements in induced polarization (IP) research have taken place, particularly with respect to spectral IP (SIP), concerning the understanding of the mechanisms of the IP phenomenon, the conduction of accurate and broadband laboratory measurements, the modelling and inversion of IF data for imaging purposes and the increasing application of the method in near-surface investigations. We summarize here the current state of the science of the SIP method for near-surface applications and describe which aspects still represent open issues and should be the focus of future research efforts. Significant progress has been made over the last decade in the understanding of the microscopic mechanisms of IP; however, integrated mechanistic models involving different possible polarization processes at the grain/pore scale are still lacking. A prerequisite for the advances in the mechanistic understanding of IP was the development of improved laboratory instrumentation, which has led to a continuously growing data base of SIP measurements on various soil and rock samples. We summarize the experience of numerous experimental studies by formulating key recommendations for reliable SIP laboratory measurements. To make use of the established theoretical and empirical relationships between SIP characteristics and target petrophysical properties at the field scale, sophisticated forward modelling and inversion algorithms are needed. Considerable progress has also been made in this field, in particular with the development of complex resistivity algorithms allowing the modelling and inversion of IF data in the frequency domain. The ultimate goal for the future are algorithms and codes for the integral inversion of 3D, time-lapse and multi-frequency IF data, which defines a 5D inversion problem involving the dimensions space (for imaging), time (for monitoring) and frequency (for spectroscopy). We also offer guidelines for reliable and accurate measurements of IP spectra, which are essential for improved understanding of IP mechanisms and their links to physical, chemical and biological properties of interest. We believe that the SIP method offers potential for subsurface structure and process characterization, in particular in hydrogeophysical and biogeophysical studies.
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| 2. |
- Martin, Tina, et al.
(author)
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SIP laboratory data: frequency-domain versus time-domain
- 2021
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Conference paper (other academic/artistic)abstract
- Spectral information from induced polarisation (IP) measurements can be used for several applications as the characterisation of the lithology, the estimation of hydraulic parameters, the localization of contaminated areas and many more.So far, the spectral content has been mainly determined in frequency domain (FD). Due to significant instrumental developments and advanced data processing and inversion tools, it is nowadays also possible to extract spectral information from time-domain (TD) measurements. Even though the results from both domains should be theoretically identical, differences can be observed in the practical application. To compare both domains, we started with numerical models and measurements at test circuits. Thereafter, we conducted measurements on different types of well-known material (e.g., sandstones and wood samples) in a controlled laboratory environment. For the TDIP measurements, the AIE-2 instrument was used and the FDIP spectra were recorded with the SIP Fuchs III device. Besides the measurement results, shown as decay curves in TD and amplitude and phase spectra in FD, also the Differential Polarisation parameter (DP) is presented. This parameter is calculated from the TD decay curve and proves to be well correlated with the phase in FD. The comparison of DP and phase curves enables a first visual check and a discrimination between different samples. To compare both domains qualitatively, the relaxation time distribution (RTD) was calculated for all data. Theresults are in (partly very) good agreement between both domains, depending on the data quality. We found that the RTDs are in better agreement for the wood samples than for the sandstone samples. We attribute the differences to the lower data quality of the TD measurements of sandstones, which were performed with lower current in comparison to the wood samples. Therefore, the TD decay curves at later times are more affected by noise.
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| 3. |
- Martin, Tina, et al.
(author)
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Spectral induced polarization: frequency domain versus time domain laboratory data
- 2021
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In: Geophysical Journal International. - : Oxford University Press (OUP). - 0956-540X .- 1365-246X. ; 225, s. 1982-2000
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Journal article (peer-reviewed)abstract
- Spectral information obtained from induced polarization (IP) measurements can be used in a variety of applications and is often gathered in frequency domain (FD) at the laboratory scale. In contrast, field IP measurements are mostly done in time domain (TD). Theoretically, the spectral content from both domains should be similar. In practice, they are often different, mainly due to instrumental restrictions as well as the limited time and frequency range ofmeasurements. Therefore, a possibility of transition between both domains, in particular for the comparison of laboratory FD IP data and field TD IP results, would be very favourable. To compare both domains, we conducted laboratory IP experiments in both TD and FD.We started with three numerical models and measurements at a test circuit, followed by several investigations for different wood and sandstone samples. Our results demonstrate that the differential polarizability (DP), which is calculated from the TD decay curves, can be compared very well with the phase of the complex electrical resistivity. Thus, DP can be used for a first visual comparison of FD and TD data, which also enables a fast discriminationbetween different samples. Furthermore, to compare both domains qualitatively, we calculated the relaxation time distribution (RTD) for all data. The results are mostly in agreement between both domains, however, depending on the TD data quality. It is striking that the DP and RTD results are in better agreement for higher data quality in TD. Nevertheless, we demonstrate that IP laboratory measurements can be carried out in both TD and FD with almost equivalentresults. The RTD enables a good comparability of FD IP laboratory data with TD IP field data.
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