You can find a searchable list of my publications below. My Google Scholar profile contains an up-to-date overview of my citations. I also have a ResearchGate profile with most of my full-texts.
I am a strong proponent of Open Access, especially after having spent more than four years as a researcher at an institution with a very limited number of journal subscriptions. For each entry below where I am legally allowed to share a full-text, you can find it as the first link of the entry.
2024
Wangensteen, Magnus; Johansen, Tonni Franke; Fatemi, Ali; Viggen, Erlend Magnus
Pipe wall thickness estimation by frequency–wavenumber analysis of circumferential guided waves Journal Article
In: Mechanical Systems and Signal Processing, vol. 1, pp. 111369, 2024.
Abstract | BibTeX | Tags: acoustics, guided waves | Links:
@article{wangensteen_pipe_2024,
title = {Pipe wall thickness estimation by frequency–wavenumber analysis of circumferential guided waves},
author = {Magnus Wangensteen and Tonni Franke Johansen and Ali Fatemi and Erlend Magnus Viggen},
doi = {https://doi.org/10.1016/j.ymssp.2024.111369},
year = {2024},
date = {2024-06-01},
urldate = {2022-12-19},
journal = {Mechanical Systems and Signal Processing},
volume = {1},
pages = {111369},
abstract = {Ultrasonic guided waves in pipes propagating in the circumferential direction carry information about the thickness of the pipe wall. This study proposes a method for estimating the pipe wall thickness based on measurements from circumferentially distributed sensors and a set of pre-computed theoretical dispersion curves. The recorded data are Fourier transformed into a frequency–wavenumber representation. The wall thickness is obtained by identifying the best fitting dispersion curve to the frequency–wavenumber data by determining the maximum stacking power. The thickness estimation method has demonstrated robustness against noise. Given the presence of significant noise (0.0 dB signal-to-noise ratio) and simulations where the thickness ranges from 6.0 to 10.0 mm, using eight sensors or more attain a mean absolute percentage error of less than 1%. The method is also supported by real laboratory measurements using eight sensor positions, where the error is less than 0.7%. Experimental measurements near the pipe end demonstrate that with appropriate positioning, end-reflections should not have a detrimental effect on the accuracy. The method estimates the mean thickness in cases where the pipe wall has near-uniform thickness but may not be as reliable when there are large shallow defects caused by metal loss, which is typically the case when the inner wall has suffered from erosion. In this case, monitoring of the stacking power curves could detect regional metal loss due to erosion and analysis of the local maxima could uncover information about individual thickness segments around the pipe circumference.},
keywords = {acoustics, guided waves},
pubstate = {published},
tppubtype = {article}
}
Ultrasonic guided waves in pipes propagating in the circumferential direction carry information about the thickness of the pipe wall. This study proposes a method for estimating the pipe wall thickness based on measurements from circumferentially distributed sensors and a set of pre-computed theoretical dispersion curves. The recorded data are Fourier transformed into a frequency–wavenumber representation. The wall thickness is obtained by identifying the best fitting dispersion curve to the frequency–wavenumber data by determining the maximum stacking power. The thickness estimation method has demonstrated robustness against noise. Given the presence of significant noise (0.0 dB signal-to-noise ratio) and simulations where the thickness ranges from 6.0 to 10.0 mm, using eight sensors or more attain a mean absolute percentage error of less than 1%. The method is also supported by real laboratory measurements using eight sensor positions, where the error is less than 0.7%. Experimental measurements near the pipe end demonstrate that with appropriate positioning, end-reflections should not have a detrimental effect on the accuracy. The method estimates the mean thickness in cases where the pipe wall has near-uniform thickness but may not be as reliable when there are large shallow defects caused by metal loss, which is typically the case when the inner wall has suffered from erosion. In this case, monitoring of the stacking power curves could detect regional metal loss due to erosion and analysis of the local maxima could uncover information about individual thickness segments around the pipe circumference.
Wangensteen, Magnus; Johansen, Tonni Franke; Fatemi, Ali; Viggen, Erlend Magnus; Haugan, Lars Eidissen
Pitting Detection and Characterization From Ultrasound Timelapse Images Using Convolutional Neural Networks Journal Article
In: IEEE Open Journal of Instrumentation and Measurement, 2024.
Abstract | BibTeX | Tags: acoustics, guided waves | Links:
@article{wangensteen_pitting_2024,
title = {Pitting Detection and Characterization From Ultrasound Timelapse Images Using Convolutional Neural Networks},
author = {Magnus Wangensteen and Tonni Franke Johansen and Ali Fatemi and Erlend Magnus Viggen and Lars Eidissen Haugan},
doi = {10.1109/OJIM.2024.3396829},
year = {2024},
date = {2024-05-06},
journal = {IEEE Open Journal of Instrumentation and Measurement},
abstract = {Pitting corrosion, a localized form of corrosion leading to cavities and structural failure in metallic materials, requires early detection for effective mitigation. While ultrasonic inspection techniques can readily detect uniform wall thinning, they often struggle to identify pitting corrosion. This study proposes a time-lapse ultrasound inspection method to detect early-stage pitting using pulse-echo sensors. By recording multiple ultrasonic traces over time, 2D timelapse images of ultrasonic reflectivity can be generated and fed into a trained neural network for pitting diagnostics. In general, training a machine learning model requires a large training dataset. This work used data from a drilling experiment to generate a suitable dataset. Dataset construction by random time-ordered combinations of ultrasonic measurements was conducted to create a diverse set of time-lapse image samples to generalize the resulting machine-learning model adequately. A classification neural network was trained to detect the presence of drilled holes, and a separate regression network was trained to estimate the hole depth. Based on drilling data from an independently acquired test dataset, results demonstrate a mean absolute error of 0.163 mm for hole depth estimations. All holes are successfully detected when 0.1 mm deeper than the defined pitting threshold of 0.5 mm. This suggests that the proposed method generalizes well and can be deployed to any similar acquisition system.},
keywords = {acoustics, guided waves},
pubstate = {published},
tppubtype = {article}
}
Pitting corrosion, a localized form of corrosion leading to cavities and structural failure in metallic materials, requires early detection for effective mitigation. While ultrasonic inspection techniques can readily detect uniform wall thinning, they often struggle to identify pitting corrosion. This study proposes a time-lapse ultrasound inspection method to detect early-stage pitting using pulse-echo sensors. By recording multiple ultrasonic traces over time, 2D timelapse images of ultrasonic reflectivity can be generated and fed into a trained neural network for pitting diagnostics. In general, training a machine learning model requires a large training dataset. This work used data from a drilling experiment to generate a suitable dataset. Dataset construction by random time-ordered combinations of ultrasonic measurements was conducted to create a diverse set of time-lapse image samples to generalize the resulting machine-learning model adequately. A classification neural network was trained to detect the presence of drilled holes, and a separate regression network was trained to estimate the hole depth. Based on drilling data from an independently acquired test dataset, results demonstrate a mean absolute error of 0.163 mm for hole depth estimations. All holes are successfully detected when 0.1 mm deeper than the defined pitting threshold of 0.5 mm. This suggests that the proposed method generalizes well and can be deployed to any similar acquisition system.
2023
Viggen, Erlend Magnus; Arnestad, Håvard Kjellmo
Modelling acoustic radiation from vibrating surfaces around coincidence: Radiation into fluids Journal Article
In: Journal of Sound and Vibration, vol. 560, pp. 20, 2023, ISBN: 0022-460X.
Abstract | BibTeX | Tags: acoustics, guided waves | Links:
@article{viggen_modelling_2023,
title = {Modelling acoustic radiation from vibrating surfaces around coincidence: Radiation into fluids},
author = {Erlend Magnus Viggen and Håvard Kjellmo Arnestad},
doi = {10.1016/j.jsv.2023.117787},
isbn = {0022-460X},
year = {2023},
date = {2023-09-15},
urldate = {2023-09-15},
journal = {Journal of Sound and Vibration},
volume = {560},
pages = {20},
abstract = {It is well-known that vibrating surfaces generate sound waves in adjacent fluids. According to the classical radiation model, the nature of these waves depends on whether the vibration’s phase speed cv is above (supersonic) or below (subsonic) the fluid sound speed cf. The transition between these two domains is known as coincidence. In the supersonic domain, the sound wave radiates into the fluid. In the subsonic domain, the classical model states that the wave becomes evanescent and clings to the surface. In the last 30 years, however, several articles on leaky guided waves have reported radiating waves in the subsonic domain, which is at odds with the classical model. In this article, we investigate an enhanced model for sound radiation near and below coincidence. Unlike the classical model, this model fully respects conservation of energy by balancing the radiated power with power lost from the guided wave underlying the vibration. The model takes into account that this power loss and the consequent attenuation of the surface vibration result in an inhomogeneous radiated sound wave — an effect that cannot be neglected near coincidence. We successfully validate the model against exact solutions for leaky A0 Lamb waves around coincidence. The model can also be used as a perturbation method to predict the attenuation of leaky A0 waves from the properties of free A0 waves, giving more accurate estimates than existing perturbation methods. We further investigate subsonic leaky A0 waves using the enhanced model. Thereby we, for example, explain the peculiar reappearance or persistence of the leaky A0 wave at lower frequencies, an effect brought to attention by previous theoretical studies.},
keywords = {acoustics, guided waves},
pubstate = {published},
tppubtype = {article}
}
It is well-known that vibrating surfaces generate sound waves in adjacent fluids. According to the classical radiation model, the nature of these waves depends on whether the vibration’s phase speed cv is above (supersonic) or below (subsonic) the fluid sound speed cf. The transition between these two domains is known as coincidence. In the supersonic domain, the sound wave radiates into the fluid. In the subsonic domain, the classical model states that the wave becomes evanescent and clings to the surface. In the last 30 years, however, several articles on leaky guided waves have reported radiating waves in the subsonic domain, which is at odds with the classical model. In this article, we investigate an enhanced model for sound radiation near and below coincidence. Unlike the classical model, this model fully respects conservation of energy by balancing the radiated power with power lost from the guided wave underlying the vibration. The model takes into account that this power loss and the consequent attenuation of the surface vibration result in an inhomogeneous radiated sound wave — an effect that cannot be neglected near coincidence. We successfully validate the model against exact solutions for leaky A0 Lamb waves around coincidence. The model can also be used as a perturbation method to predict the attenuation of leaky A0 waves from the properties of free A0 waves, giving more accurate estimates than existing perturbation methods. We further investigate subsonic leaky A0 waves using the enhanced model. Thereby we, for example, explain the peculiar reappearance or persistence of the leaky A0 wave at lower frequencies, an effect brought to attention by previous theoretical studies.
Johansen, Tonni Franke; Buschmann, Philip Erik; Røsberg, Knut Marius; Diez, Anja; Viggen, Erlend Magnus
Ultrasonic well integrity logging using phased array technology Proceedings Article
In: Proceedings of the ASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering, pp. 9, American Society of Mechanical Engineers, 2023, ISBN: 978-0-7918-8691-5.
Abstract | BibTeX | Tags: guided waves, well logging | Links:
@inproceedings{johansen_ultrasonic_2023,
title = {Ultrasonic well integrity logging using phased array technology},
author = {Tonni Franke Johansen and Philip Erik Buschmann and Knut Marius Røsberg and Anja Diez and Erlend Magnus Viggen},
url = {https://hdl.handle.net/11250/3102191, Full-text on NTNU Open},
doi = {10.1115/OMAE2023-108101},
isbn = {978-0-7918-8691-5},
year = {2023},
date = {2023-06-11},
urldate = {2023-06-11},
booktitle = {Proceedings of the ASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering},
volume = {9},
pages = {9},
publisher = {American Society of Mechanical Engineers},
abstract = {Ultrasonic well integrity logging is an important and common procedure for well completion and plug-and-abandonment operations. Typical logging tools employ single-element ultrasound transducers. In medical ultrasound imaging, however, more flexible phased arrays are the standard. This paper presents a first set of experimental results obtained with up to two linear 32-element phased arrays that are specifically designed for plug-and-abandonment operations in terms of their centre frequency. The experiments encompass pulse-echo and pitch-catch studies for different incidence angles and aperture sizes on plates and pipes with wall thickness as encountered in the offshore industry. The pulse-echo experiment is backed up by simulations, and shows that effect of the incidence angle on the pipe resonance’s frequency and strength is weak and more strong, respectively, and that the effect depends on the frequency response and directivity of the transducer. The pitch-catch experiment demonstrates the importance of carefully choosing the right angle of incidence to excite the intended wave modes.},
keywords = {guided waves, well logging},
pubstate = {published},
tppubtype = {inproceedings}
}
Ultrasonic well integrity logging is an important and common procedure for well completion and plug-and-abandonment operations. Typical logging tools employ single-element ultrasound transducers. In medical ultrasound imaging, however, more flexible phased arrays are the standard. This paper presents a first set of experimental results obtained with up to two linear 32-element phased arrays that are specifically designed for plug-and-abandonment operations in terms of their centre frequency. The experiments encompass pulse-echo and pitch-catch studies for different incidence angles and aperture sizes on plates and pipes with wall thickness as encountered in the offshore industry. The pulse-echo experiment is backed up by simulations, and shows that effect of the incidence angle on the pipe resonance’s frequency and strength is weak and more strong, respectively, and that the effect depends on the frequency response and directivity of the transducer. The pitch-catch experiment demonstrates the importance of carefully choosing the right angle of incidence to excite the intended wave modes.
Wangensteen, Magnus; Johansen, Tonni Franke; Fatemi, Ali; Viggen, Erlend Magnus
Ultrasonic Guided Waves and Machine Learning for Corrosion Monitoring in Steel Pipes Proceedings Article
In: AMPP Annual Conference + Expo, pp. 12, Association for Materials Protection and Performance, 2023.
Abstract | BibTeX | Tags: acoustics, guided waves | Links:
@inproceedings{wangensteen_ultrasonic_2023,
title = {Ultrasonic Guided Waves and Machine Learning for Corrosion Monitoring in Steel Pipes},
author = {Magnus Wangensteen and Tonni Franke Johansen and Ali Fatemi and Erlend Magnus Viggen},
url = {https://onepetro.org/amppcorr/proceedings/AMPP23/All-AMPP23/AMPP-2023-19289/527075, Paper on OnePetro},
year = {2023},
date = {2023-03-19},
urldate = {2023-03-19},
booktitle = {AMPP Annual Conference + Expo},
pages = {12},
publisher = {Association for Materials Protection and Performance},
abstract = {In a pipe, a circumferentially travelling ultrasonic wave will gather information about the properties and boundaries of the propagation medium. However, the compounded effects of diagnostic features like mean pipe wall thinning, surface roughness, regional depressions, and pit developments are difficult to separate using traditional methods. Therefore, this study proposes an approach using artificial neural networks to estimate the diagnostic features of interest.
This study is based on ultrasound simulations and synthetic data. The synthetic data is recorded at a set of transducer positions at the outer pipe wall. The resulting traces are then combined into 2D images where each vertical line represents the waveform recorded at a specific transducer location. The resulting images are used to train a neural network to extract relevant features.
Diagnostic features for mean and minimum thickness, as well as standard deviation of the wall thickness, are quite accurately estimated. The neural network-based estimation for mean thickness is more accurate than a conventional reference method. This is observed especially for non-uniform wall thickness, which is typically the case if the pipe wall has been exposed to erosion and corrosion. Features for depth and location of depressions are also informative but less accurate. Data decimation experiments have also been conducted, even down to one single remaining trace. Also in this case, the neural network is able to make good estimates of some features, especially the mean wall thickness.},
keywords = {acoustics, guided waves},
pubstate = {published},
tppubtype = {inproceedings}
}
In a pipe, a circumferentially travelling ultrasonic wave will gather information about the properties and boundaries of the propagation medium. However, the compounded effects of diagnostic features like mean pipe wall thinning, surface roughness, regional depressions, and pit developments are difficult to separate using traditional methods. Therefore, this study proposes an approach using artificial neural networks to estimate the diagnostic features of interest.
This study is based on ultrasound simulations and synthetic data. The synthetic data is recorded at a set of transducer positions at the outer pipe wall. The resulting traces are then combined into 2D images where each vertical line represents the waveform recorded at a specific transducer location. The resulting images are used to train a neural network to extract relevant features.
Diagnostic features for mean and minimum thickness, as well as standard deviation of the wall thickness, are quite accurately estimated. The neural network-based estimation for mean thickness is more accurate than a conventional reference method. This is observed especially for non-uniform wall thickness, which is typically the case if the pipe wall has been exposed to erosion and corrosion. Features for depth and location of depressions are also informative but less accurate. Data decimation experiments have also been conducted, even down to one single remaining trace. Also in this case, the neural network is able to make good estimates of some features, especially the mean wall thickness.
This study is based on ultrasound simulations and synthetic data. The synthetic data is recorded at a set of transducer positions at the outer pipe wall. The resulting traces are then combined into 2D images where each vertical line represents the waveform recorded at a specific transducer location. The resulting images are used to train a neural network to extract relevant features.
Diagnostic features for mean and minimum thickness, as well as standard deviation of the wall thickness, are quite accurately estimated. The neural network-based estimation for mean thickness is more accurate than a conventional reference method. This is observed especially for non-uniform wall thickness, which is typically the case if the pipe wall has been exposed to erosion and corrosion. Features for depth and location of depressions are also informative but less accurate. Data decimation experiments have also been conducted, even down to one single remaining trace. Also in this case, the neural network is able to make good estimates of some features, especially the mean wall thickness.
2022
Arnestad, Håvard Kjellmo; Viggen, Erlend Magnus
A fast simulation method for Lamb wave propagation in coupled non-parallel plates Presentation
Poster presented at the IEEE International Ultrasonics Symposium 2022, 12.10.2022.
Abstract | BibTeX | Tags: acoustics, guided waves, well logging | Links:
@misc{nokey,
title = {A fast simulation method for Lamb wave propagation in coupled non-parallel plates},
author = {Håvard Kjellmo Arnestad and Erlend Magnus Viggen},
url = {https://www.researchgate.net/publication/364359505_A_fast_simulation_method_for_Lamb_wave_propagation_in_coupled_non-parallel_plates, Poster on ResearchGate},
year = {2022},
date = {2022-10-12},
urldate = {2022-10-12},
abstract = {Some systems in ultrasonic testing can be approximated as two non-parallel plates coupled by a fluid, where leaky Lamb waves propagate in each plate. This work develops a fast and accurate simulation method for such systems by extending methods based on the theory of layered media to non-parallel surfaces. The aim is to determine the presence of cement through two steel plates via inversion. The method runs roughly 10 000 times faster than equivalent simulations in COMSOL. Three-dimensional propagation is also shown, and a mechanism based on Lamb mode conversion between tilted plates is explained.},
howpublished = {Poster presented at the IEEE International Ultrasonics Symposium 2022},
keywords = {acoustics, guided waves, well logging},
pubstate = {published},
tppubtype = {presentation}
}
Some systems in ultrasonic testing can be approximated as two non-parallel plates coupled by a fluid, where leaky Lamb waves propagate in each plate. This work develops a fast and accurate simulation method for such systems by extending methods based on the theory of layered media to non-parallel surfaces. The aim is to determine the presence of cement through two steel plates via inversion. The method runs roughly 10 000 times faster than equivalent simulations in COMSOL. Three-dimensional propagation is also shown, and a mechanism based on Lamb mode conversion between tilted plates is explained.
2021
Arnestad, Håvard Kjellmo; Viggen, Erlend Magnus
A fast semi-analytical method for propagating leaky Lamb wavefields Proceedings Article
In: Proceedings of the 44th Scandinavian Symposium on Physical Acoustics, pp. 22, Norwegian Physical Society, Online, 2021, ISBN: 978-82-8123-021-71.
Abstract | BibTeX | Tags: acoustics, guided waves | Links:
@inproceedings{arnestad_fast_2021,
title = {A fast semi-analytical method for propagating leaky Lamb wavefields},
author = {Håvard Kjellmo Arnestad and Erlend Magnus Viggen},
url = {https://www.researchgate.net/publication/351005828_A_fast_semi-analytical_method_for_propagating_leaky_Lamb_wavefields, Full-text on ResearchGate},
isbn = {978-82-8123-021-71},
year = {2021},
date = {2021-04-01},
urldate = {2021-04-01},
booktitle = {Proceedings of the 44th Scandinavian Symposium on Physical Acoustics},
pages = {22},
publisher = {Norwegian Physical Society},
address = {Online},
abstract = {A fast method is presented for calculating the wavefields from initialized leaky Lamb waves on plates immersed in sufficiently light fluids. The method works by precomputing the dispersion relation and attenuation, and propagating the wavefields in the frequency domain. An angular spectrum approach is used to include leakage into surrounding fluid. Compared to matching FEM simulations, the computations are performed in the order of seconds, rather than hours. The method also benefits from being much easier to set up correctly, but is on the other hand less general in that it cannot handle e.g. scattering from defects. The correspondence is shown to be good for the case of interest.},
keywords = {acoustics, guided waves},
pubstate = {published},
tppubtype = {inproceedings}
}
A fast method is presented for calculating the wavefields from initialized leaky Lamb waves on plates immersed in sufficiently light fluids. The method works by precomputing the dispersion relation and attenuation, and propagating the wavefields in the frequency domain. An angular spectrum approach is used to include leakage into surrounding fluid. Compared to matching FEM simulations, the computations are performed in the order of seconds, rather than hours. The method also benefits from being much easier to set up correctly, but is on the other hand less general in that it cannot handle e.g. scattering from defects. The correspondence is shown to be good for the case of interest.
2017
Viggen, Erlend Magnus; Johansen, Tonni Franke; Merciu, Ioan-Alexandru
Simulation and inversion of ultrasonic pitch-catch through-tubing well logging with an array of receivers Journal Article
In: NDT & E International, vol. 85, pp. 72–75, 2017, ISSN: 09638695.
Abstract | BibTeX | Tags: acoustics, guided waves, well logging | Links:
@article{viggen_simulation_2017,
title = {Simulation and inversion of ultrasonic pitch-catch through-tubing well logging with an array of receivers},
author = {Erlend Magnus Viggen and Tonni Franke Johansen and Ioan-Alexandru Merciu},
url = {https://erlend-viggen.no/wp-content/uploads/2018/04/viggen_simulation_2017_post-print.pdf, Full-text},
doi = {10.1016/j.ndteint.2016.10.008},
issn = {09638695},
year = {2017},
date = {2017-01-01},
urldate = {2017-01-01},
journal = {NDT & E International},
volume = {85},
pages = {72--75},
abstract = {Current methods for ultrasonic pitch-catch well logging use two receivers to log the bonded material outside a single casing. For two casings separated by a fluid, we find by simulation that increasing the number of receivers provides a better picture of the effect of the bonded material outside the second casing. Inverting simulated measurements with five receivers, using a simulated annealing algorithm and a simple forward model, we find for a subset of simulations that we can estimate the impedance of the material outside the outer casing.},
keywords = {acoustics, guided waves, well logging},
pubstate = {published},
tppubtype = {article}
}
Current methods for ultrasonic pitch-catch well logging use two receivers to log the bonded material outside a single casing. For two casings separated by a fluid, we find by simulation that increasing the number of receivers provides a better picture of the effect of the bonded material outside the second casing. Inverting simulated measurements with five receivers, using a simulated annealing algorithm and a simple forward model, we find for a subset of simulations that we can estimate the impedance of the material outside the outer casing.
2016
Viggen, Erlend Magnus; Johansen, Tonni Franke; Merciu, Ioan-Alexandru
Simulation and modeling of ultrasonic pitch-catch through-tubing logging Journal Article
In: Geophysics, vol. 81, no. 4, pp. D383-D393, 2016.
Abstract | BibTeX | Tags: acoustics, guided waves, well logging | Links:
@article{viggen_simulation_2016,
title = {Simulation and modeling of ultrasonic pitch-catch through-tubing logging},
author = {Erlend Magnus Viggen and Tonni Franke Johansen and Ioan-Alexandru Merciu},
url = {https://erlend-viggen.no/wp-content/uploads/2018/04/viggen_simulation_2016.pdf, Full-text},
doi = {10.1190/geo2015-0251.1},
year = {2016},
date = {2016-07-01},
urldate = {2016-07-01},
journal = {Geophysics},
volume = {81},
number = {4},
pages = {D383-D393},
abstract = {Cased petroleum wells must be logged to determine the bonding and hydraulic isolation properties of the sealing material and to determine the structural integrity status. Although ultrasonic pitch-catch logging in single-casing geometries has been widely studied and is commercially available, this is not the case for logging in double-casing geometries despite its increasing importance in plug and abandonment operations. It is therefore important to investigate whether existing logging tools can be used in such geometries. Using a finite-element model of a double-casing geometry with a two-receiver pitch-catch setup, we have simulated through-tubing logging, with fluid between the two casings. We found that there appears a cascade of leaky Lamb wave packets on both casings, linked by leaked wavefronts. By varying the geometry and materials in the model, we have examined the effect on the pulse received from the second wave packet on the inner casing, sometimes known as the third interface echo. The amplitude of this pulse was found to contain information on the bonded material in the outer annulus. Much stronger amplitude variations were found with two equally thick casings than with a significant thickness difference; relative thickness differences of up to one-third were simulated. Finally, we have developed a simple mathematical model of the wave packets’ time evolution to encapsulate and validate our understanding of the wave packet cascade. This model shows a more complex time evolution in the later wave packets than the exponentially attenuated primary packet, which is currently used for single-casing logging. This indicates that tools with more than two receivers, which could measure wave packets’ amplitude at more than two points along their time evolution, would be able to draw more information from these later packets. The model was validated against simulations, finding good agreement when the underlying assumptions of the model were satisfied.},
keywords = {acoustics, guided waves, well logging},
pubstate = {published},
tppubtype = {article}
}
Cased petroleum wells must be logged to determine the bonding and hydraulic isolation properties of the sealing material and to determine the structural integrity status. Although ultrasonic pitch-catch logging in single-casing geometries has been widely studied and is commercially available, this is not the case for logging in double-casing geometries despite its increasing importance in plug and abandonment operations. It is therefore important to investigate whether existing logging tools can be used in such geometries. Using a finite-element model of a double-casing geometry with a two-receiver pitch-catch setup, we have simulated through-tubing logging, with fluid between the two casings. We found that there appears a cascade of leaky Lamb wave packets on both casings, linked by leaked wavefronts. By varying the geometry and materials in the model, we have examined the effect on the pulse received from the second wave packet on the inner casing, sometimes known as the third interface echo. The amplitude of this pulse was found to contain information on the bonded material in the outer annulus. Much stronger amplitude variations were found with two equally thick casings than with a significant thickness difference; relative thickness differences of up to one-third were simulated. Finally, we have developed a simple mathematical model of the wave packets’ time evolution to encapsulate and validate our understanding of the wave packet cascade. This model shows a more complex time evolution in the later wave packets than the exponentially attenuated primary packet, which is currently used for single-casing logging. This indicates that tools with more than two receivers, which could measure wave packets’ amplitude at more than two points along their time evolution, would be able to draw more information from these later packets. The model was validated against simulations, finding good agreement when the underlying assumptions of the model were satisfied.
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