Three-dimensional time-lapse inversion of transient electromagnetic data, with application at an Icelandic geothermal site

Longying Xiao; Gianluca Fiandaca; Pradip K. Maurya; Anders Vest Christiansen; Léa Lévy

doi:10.1093/gji/ggac206

Three-dimensional time-lapse inversion of transient electromagnetic data, with application at an Icelandic geothermal site

Longying Xiao^*, Gianluca Fiandaca, Pradip K. Maurya, Anders Vest Christiansen, Léa Lévy

^*Corresponding author for this work

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Abstract

Transient electromagnetic (TEM) is an efficient non-invasive method to map electrical conductivity distribution in the subsurface. This paper presents an inversion scheme for 3-D TEM time-lapse (TL) data using a generalized minimum support (MS) norm and its application to monitoring conductivity changes over time. In particular, two challenges for TL TEM applications are addressed: (i) the survey repetition with slightly different acquisition position, that is, because systems are not installed and (ii) non-optimal data coverage above the TL anomalies, for instance, due to the presence of infrastructure that limits the acquisition layout because of coupling. To address these issues, we developed a new TEM TL inversion scheme with the following features: (1) a multimesh approach for model definition and forward computations, which allows for seamless integration of data sets with different acquisition layouts; (2) 3-D sensitivity calculation during the inversion, which allows retrieving conductivity changes in-between TEM soundings and (3) simultaneous inversion of two data sets at once, imposing TL constraints defined in terms of a generalized MS norm, which ensures compact TL changes. We assess the relevance of our implementations through a synthetic example and a field example. In the synthetic example, we study the capability of the inversion scheme to retrieve compact time-lapse changes despite slight changes in the acquisition layout and the effect of data coverage on the retrieval of TL changes. Results from the synthetic tests are used for interpreting field data, which consists of two TEM data sets collected in 2019 and 2020 at the Nesjavellir high-temperature geothermal site (Iceland) within a monitoring project of H2S sequestration. Furthermore, the field example illustrates the effect of the trade-off between data misfit and TL constraints in the inversion objective function, using the tuning settings of the generalized MS norm. Based on the results from both the synthetic and field cases, we show that our implementation of 3-D TL inversion has a robust performance for TEM monitoring.

Original language	English
Journal	Geophysical Journal International
Volume	231
Issue	1
Pages (from-to)	584-596
Number of pages	13
ISSN	0956-540X
DOIs	https://doi.org/10.1093/gji/ggac206
Publication status	Published - Oct 2022

Keywords

Controlled source electromagnetics (CSEM)
Hydrogeophysics
Inverse theory
Time-domain electromagnetic
Time-lapse inversion

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10.1093/gji/ggac206

Three-dimensional time-lapse inversion of transient electromagnetic data, with application at an Icelandic geothermal siteFinal published version, 4.35 MB

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title = "Three-dimensional time-lapse inversion of transient electromagnetic data, with application at an Icelandic geothermal site",

abstract = "Transient electromagnetic (TEM) is an efficient non-invasive method to map electrical conductivity distribution in the subsurface. This paper presents an inversion scheme for 3-D TEM time-lapse (TL) data using a generalized minimum support (MS) norm and its application to monitoring conductivity changes over time. In particular, two challenges for TL TEM applications are addressed: (i) the survey repetition with slightly different acquisition position, that is, because systems are not installed and (ii) non-optimal data coverage above the TL anomalies, for instance, due to the presence of infrastructure that limits the acquisition layout because of coupling. To address these issues, we developed a new TEM TL inversion scheme with the following features: (1) a multimesh approach for model definition and forward computations, which allows for seamless integration of data sets with different acquisition layouts; (2) 3-D sensitivity calculation during the inversion, which allows retrieving conductivity changes in-between TEM soundings and (3) simultaneous inversion of two data sets at once, imposing TL constraints defined in terms of a generalized MS norm, which ensures compact TL changes. We assess the relevance of our implementations through a synthetic example and a field example. In the synthetic example, we study the capability of the inversion scheme to retrieve compact time-lapse changes despite slight changes in the acquisition layout and the effect of data coverage on the retrieval of TL changes. Results from the synthetic tests are used for interpreting field data, which consists of two TEM data sets collected in 2019 and 2020 at the Nesjavellir high-temperature geothermal site (Iceland) within a monitoring project of H2S sequestration. Furthermore, the field example illustrates the effect of the trade-off between data misfit and TL constraints in the inversion objective function, using the tuning settings of the generalized MS norm. Based on the results from both the synthetic and field cases, we show that our implementation of 3-D TL inversion has a robust performance for TEM monitoring. ",

keywords = "Controlled source electromagnetics (CSEM), Hydrogeophysics, Inverse theory, Time-domain electromagnetic, Time-lapse inversion",

author = "Longying Xiao and Gianluca Fiandaca and Maurya, {Pradip K.} and Christiansen, {Anders Vest} and L{\'e}a L{\'e}vy",

note = "Publisher Copyright: {\textcopyright} 2022 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society.",

year = "2022",

month = oct,

doi = "10.1093/gji/ggac206",

language = "English",

volume = "231",

pages = "584--596",

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issn = "0956-540X",

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Three-dimensional time-lapse inversion of transient electromagnetic data, with application at an Icelandic geothermal site. / Xiao, Longying; Fiandaca, Gianluca; Maurya, Pradip K. et al.
In: Geophysical Journal International, Vol. 231, No. 1, 10.2022, p. 584-596.

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

TY - JOUR

T1 - Three-dimensional time-lapse inversion of transient electromagnetic data, with application at an Icelandic geothermal site

AU - Xiao, Longying

AU - Fiandaca, Gianluca

AU - Maurya, Pradip K.

AU - Christiansen, Anders Vest

AU - Lévy, Léa

PY - 2022/10

Y1 - 2022/10

N2 - Transient electromagnetic (TEM) is an efficient non-invasive method to map electrical conductivity distribution in the subsurface. This paper presents an inversion scheme for 3-D TEM time-lapse (TL) data using a generalized minimum support (MS) norm and its application to monitoring conductivity changes over time. In particular, two challenges for TL TEM applications are addressed: (i) the survey repetition with slightly different acquisition position, that is, because systems are not installed and (ii) non-optimal data coverage above the TL anomalies, for instance, due to the presence of infrastructure that limits the acquisition layout because of coupling. To address these issues, we developed a new TEM TL inversion scheme with the following features: (1) a multimesh approach for model definition and forward computations, which allows for seamless integration of data sets with different acquisition layouts; (2) 3-D sensitivity calculation during the inversion, which allows retrieving conductivity changes in-between TEM soundings and (3) simultaneous inversion of two data sets at once, imposing TL constraints defined in terms of a generalized MS norm, which ensures compact TL changes. We assess the relevance of our implementations through a synthetic example and a field example. In the synthetic example, we study the capability of the inversion scheme to retrieve compact time-lapse changes despite slight changes in the acquisition layout and the effect of data coverage on the retrieval of TL changes. Results from the synthetic tests are used for interpreting field data, which consists of two TEM data sets collected in 2019 and 2020 at the Nesjavellir high-temperature geothermal site (Iceland) within a monitoring project of H2S sequestration. Furthermore, the field example illustrates the effect of the trade-off between data misfit and TL constraints in the inversion objective function, using the tuning settings of the generalized MS norm. Based on the results from both the synthetic and field cases, we show that our implementation of 3-D TL inversion has a robust performance for TEM monitoring.

AB - Transient electromagnetic (TEM) is an efficient non-invasive method to map electrical conductivity distribution in the subsurface. This paper presents an inversion scheme for 3-D TEM time-lapse (TL) data using a generalized minimum support (MS) norm and its application to monitoring conductivity changes over time. In particular, two challenges for TL TEM applications are addressed: (i) the survey repetition with slightly different acquisition position, that is, because systems are not installed and (ii) non-optimal data coverage above the TL anomalies, for instance, due to the presence of infrastructure that limits the acquisition layout because of coupling. To address these issues, we developed a new TEM TL inversion scheme with the following features: (1) a multimesh approach for model definition and forward computations, which allows for seamless integration of data sets with different acquisition layouts; (2) 3-D sensitivity calculation during the inversion, which allows retrieving conductivity changes in-between TEM soundings and (3) simultaneous inversion of two data sets at once, imposing TL constraints defined in terms of a generalized MS norm, which ensures compact TL changes. We assess the relevance of our implementations through a synthetic example and a field example. In the synthetic example, we study the capability of the inversion scheme to retrieve compact time-lapse changes despite slight changes in the acquisition layout and the effect of data coverage on the retrieval of TL changes. Results from the synthetic tests are used for interpreting field data, which consists of two TEM data sets collected in 2019 and 2020 at the Nesjavellir high-temperature geothermal site (Iceland) within a monitoring project of H2S sequestration. Furthermore, the field example illustrates the effect of the trade-off between data misfit and TL constraints in the inversion objective function, using the tuning settings of the generalized MS norm. Based on the results from both the synthetic and field cases, we show that our implementation of 3-D TL inversion has a robust performance for TEM monitoring.

KW - Controlled source electromagnetics (CSEM)

KW - Hydrogeophysics

KW - Inverse theory

KW - Time-domain electromagnetic

KW - Time-lapse inversion

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U2 - 10.1093/gji/ggac206

DO - 10.1093/gji/ggac206

M3 - Journal article

AN - SCOPUS:85134391325

SN - 0956-540X

VL - 231

SP - 584

EP - 596

JO - Geophysical Journal International

JF - Geophysical Journal International

IS - 1

ER -

Three-dimensional time-lapse inversion of transient electromagnetic data, with application at an Icelandic geothermal site

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