The exploration of porphyry deposits in Greenland has become increasingly important due to their significant economic potential. We utilized total magnetic intensity (TMI) and mobile magnetotelluric (MobileMT) airborne data to delineate potential porphyry mineralization zones. The TMI method was employed to map variations in the Earth’s magnetic field caused by subsurface geological features, including mineral deposits. By analyzing anomalies in TMI data, potential porphyry targets were identified based on characteristic magnetic signatures associated with mineralized zones. Complementing TMI data, MT airborne surveys provided valuable insights into the electrical conductivity structure of the subsurface. Porphyry deposits exhibited distinct conductivity signatures due to the presence of disseminated sulfide minerals, aiding in their identification and delineation. Integration of the TMI and MobileMT datasets allowed for a comprehensive assessment of porphyry exploration targets in Flammefjeld. The combined approach facilitates the identification of prospective areas with enhanced geological potential, optimizing resource allocation and exploration efforts. Overall, this study demonstrates the efficacy of integrating TMI and MobileMT airborne data for porphyry exploration in Greenland, offering valuable insights for mineral exploration and resource development in the region.

This paper presents a new geophysical method of reservoir characterization and monitoring using the measurements of the controlled source time domain electromagnetic data by highly-sensitive SQUID (Superconducting Quantum Interference Device) magnetic sensors (SQUID-TEM). We have conducted a feasibility study of the SQUID-TEM survey for reservoir monitoring during CO2 sequestration in the Middle East test site. The SQUID-TEM measurements have been made before and after seawater/CO2 fluid injection into the subsurface reservoir. The goal was to produce 3D resistivity models around the injection borehole before and after the seawater/CO2 fluid injection and determine the injected fluid’s location after the injection. The results of the inversion of the post-injection survey data clearly showed the location of the conductive zone associated with the injected seawater/CO2 in the reservoir.

Summary The Western Superior region is part of the Canadian shield and is located north from the Superior Lake. The area has huge economic significance because several gold and base metal mineral deposits can be found there. Magnetotellurics is a useful tool to investigate the deep structure of the craton and find geological connections with the existing ore deposits. In this paper we present the results of magnetotelluric (MT) inversion of a subset of Lithoprobe and EartScope data collection covering this region. 92 MT stations were selected for 3D inversion, 79 from the Lithoprobe project and 13 from the EarthScope database. The regularized Gauss-Newton method was used applying data-space implementation. The algorithm inverts the full MT impedance and tipper data simultaneously. Based on the results, several conductive anomalies were identified in the Earth’s crust and upper mantle. Recovered 3D conductivity model was compared with known tectonic structures, earlier geoelectric studies and seismic measurements. The deepest conductor appeared below the depth of 300 km. Three elongated quasi-vertical conductive anomalies between 100 and 300 km depth may represent the zones of partially melted material rising through the upper mantle.

Geothermal energy has become an attractive renewable source of energy around the globe. Developing effective geophysical methods for geothermal exploration is vital for studying these resources. It is well known that electric conductivity is an important indicator of the location of geothermal sources. One of the most widely used geophysical techniques for analyzing the deep electrical conductivity structure is the magnetotelluric (MT) method. At the same time, the airborne electromagnetic (EM) surveys represent effective methods for the near-surface conductivity study. In this paper, we jointly analyze the Helicopter Transient Electromagnetic (HeliTEM) and magnetotelluric (MT) data acquired in some geothermal areas of Japan. The advantage of this approach over the analysis of the MT data alone is related to the fact that MT data are strongly affected by the near-surface inhomogeneities. Furthermore, the airborne HeliTEM data provide complementary information about the near-surface conductivity distribution, which we use to constrain the results of MT inversion. Thus, the joint interpretation of MT and HeliTEM data produces more reliable information about the deep conductivity model. This paper discusses the methods of 3D inversion of HeliTEM data and how to use these data in 3D MT inversion. The developed approach to the joint interpretation of the HeliTEM and MT data is illustrated by practical inversion of the HeliTEM and MT data collected over the geothermal field in Japan.

Extensive geophysical surveys were conducted over the geothermal field by Japan Oil, Gas and Metals National Corporation (JOGMEC) and Idemitsu Kosan Co. Ltd. (Idemitsu), which included airborne gravity gradiometry (AGG) and magnetotelluric (MT) surveys. The goal of this project was to study the location and structure of geothermal energy sources in the surveys area. The observed AGG and MT data were analyzed separately and jointly using 3D inversion methods. For joint inversion, we used the approach based on Gramian constraints (Zhdanov et al., 2012; Zhdanov, 2015). The Gramian method enforces the correlation between the different physical parameters of the inverse models, or their transforms, thus ensuring that the inversion produces a consistent image of the subsurface geological formation. This paper summarizes the principles of the joint inversion algorithm used in the project. We also present the results of the standalone and joint inversions to demonstrate the effectiveness of the developed method for geothermal resource exploration.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2020Feasibility study of reservoir monitoring in an onshore oil field using SQUITEM systemAuthors: Michael ZhdanovLeif CoxAlex GribenkoHideaki BanHiroshi ChibaMichael ZhdanovTechnoImaging and University of UtahSearch for more papers by this author, Leif CoxTechnoImaging and University of UtahSearch for more papers by this author, Alex GribenkoTechnoImaging and University of UtahSearch for more papers by this author, Hideaki BanJOGMECSearch for more papers by this author, and Hiroshi ChibaJOGMECSearch for more papers by this authorhttps://doi.org/10.1190/segam2020-3427120.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail AbstractThe ability to understand and control the behavior of the hydrocarbon (HC) reservoir over the production allows for optimization of reservoir performance and production strategies. The use of seismic data for water flooding monitoring is very challenging because of the small variation of seismic velocities over time and because of the difficulty of survey repeatability. There is a growing interest in developing innovative geophysical methods for monitoring hydrocarbon reservoirs. This paper introduces a feasibility study of using the highly sensitive SQUID magnetometers for reservoir monitoring in an onshore oil field. The proposed approach is based on measuring the time domain electromagnetic response from a reservoir by a set of JOGMEC developed SQUID sensors, located on the ground. The EM field is generated by an electric bipole source, or a combination of electric bipoles sending the electric pulses in the ground. We identify this survey system as a SQUITEM. This paper describes the results of the feasibility study conducted by JOGMEC and TechnoImaging to optimize the SQUITEM survey parameters. We have performed 3D modeling on a variety of survey configurations with the reservoir geometry to optimize future surveys and to develop a recommendation for an optimal SQUITEM survey for HC reservoir monitoring in an onshore oil field. The modeling shows that creating a vertical flow of current will couple better with the resistive reservoir than the typically used horizontal electric bipole source. This can be achieved by a vertical bipole source or by a ground source configuration which simulates the vertical dipole, such as a circular, star, or cross bipole configuration.Presentation Date: Tuesday, October 13, 2020Session Start Time: 1:50 PMPresentation Time: 3:30 PMLocation: Poster Station 7Presentation Type: PosterKeywords: electromagnetics, reservoir characterization, 3D, modelingPermalink: https://doi.org/10.1190/segam2020-3427120.1FiguresReferencesRelatedDetails SEG Technical Program Expanded Abstracts 2020ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2020 Pages: 3887 publication data© 2020 Published in electronic format with permission by the Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 30 Sep 2020 CITATION INFORMATION Michael Zhdanov, Leif Cox, Alex Gribenko, Hideaki Ban, and Hiroshi Chiba, (2020), "Feasibility study of reservoir monitoring in an onshore oil field using SQUITEM system," SEG Technical Program Expanded Abstracts : 601-605. https://doi.org/10.1190/segam2020-3427120.1 Plain-Language Summary Keywordselectromagneticsreservoir characterization3DmodelingPDF DownloadLoading ...

Summary Exploration and development of geothermal fields requires quantitative interpretation of different geophysical data. In this paper, we introduce the novel approach to three-dimensional inversion and interpretation of multimodal geophysical data, which incorporates the known geological/geophysical constraints. In a general case, geophysical inverse problem is ill-posed, i.e., it is non-unique and unstable; however, appropriate a priori information can help reducing the nonuniqueness and increasing the stability of this ill-posed problem. The developed approach uses the principles of inversion “guided” by known information. In the framework of this approach, the 3D inversion itself is data driven, but a priori geological/geophysical model is used as the initial and reference model during the iterative inversion process. We have applied the developed method to the integrated interpretation of magnetotelluric, gravity, and magnetic data in Yamagawa geothermal field of Japan, using the constraints based on seismic and well-logging data acquired in the same area. The results have demonstrated that the developed method produces reliable 3D models of different physical properties, which provide a solid basis for geological interpretation of the complex subsurface structures in the survey area, critical for geothermal exploration.

In this paper, we have developed a novel approach to three-dimensional inversion and interpretation of multimodal geophysical data, which incorporates known geological/geophysical constraints. In a general case, the geophysical inverse problem is ill posed, i.e., it is non-unique and unstable. However, appropriate a priori information can help reduce the non-uniqueness and increase the stability of the ill-posed problem. The developed approach uses the principles of inversion “guided” by known information. In the framework of this approach, the 3D inversion itself is data driven, but a priori geological/geophysical model is used as the initial and reference model during the iterative inversion process. We have applied the developed method to the integrated interpretation of magnetotelluric, gravity, and magnetic acquired in Yamagawa geothermal field of Japan, using constraints based on seismic and well-log data acquired in the same area. The results have demonstrated that the developed method produces reliable 3D models of different physical properties, which provides a solid basis for geological interpretation of the complex subsurface structures in the survey area, critical for geothermal exploration. Presentation Date: Wednesday, October 17, 2018 Start Time: 8:30:00 AM Location: 213A (Anaheim Convention Center) Presentation Type: Oral

独立行政法人石油天然ガス・金属資源機構（JOGMEC）が地熱発電技術研究開発事業として実施する地熱貯留層探査技術開発では，地熱開発での掘削成功率やフィールドの長期経済性の向上において求められる地熱貯留層構造の3次元的詳細把握の課題に対し，電磁探査，重力探査，磁気探査，及び弾性波探査の統合物理探査技術の開発を行ってきた。平成27年度には阿多カルデラ内部に位置する鹿児島県山川地熱地域において，第1回実証試験として3次元弾性波探査実証試験が実施され，平成28年度には既存のMTデータ，重力データ，磁気データを用いた3次元逆解析が実施された。物理探査データの3次元逆問題は，一般的にill-posedであることが知られている。一方で，複雑な地質構造を解釈するためには，信頼性の高い3次元モデルを得る必要がある。地下の地質構造を反映したモデルを初期モデルとして与えた3次元逆解析手法がこの問題を解決する手助けとなることが期待される。本研究では，山川地熱地域における弾性波探査データや坑井データ等の既知情報を統合した先験的モデルを初期モデルとし，MTデータ，重力データ，磁気データの3次元逆解析を実施した。本稿では，先験的モデルの構築において，弾性波探査データからの情報を加味することの利点を探るとともに，RMSミスフィットや坑井データと比較することで弾性波探査データからの寄与の度合いによる3次元逆解析結果の違いを検証する。

We have developed a multi-level parallel magnetotelluric (MT) integral equation based inversion program which uses variable sensitivity domain. The limited sensitivity of the data, which decreases with increasing frequency, is exploited by a receiver sensitivity domain, which also varies with frequency. We assess the effect of inverting principal, full impedance tensor, and full tensor with magnetovariational data (tipper). We first apply this method to several models and then invert the EarthScope MT data. We recover well the prominent features in the area including resistive structure associated with the Juan de Fuca slab subducting beneath the northwestern United States, the conductive zone of partially melted material above the subducting slab at the Cascade volcanic arc, conductive features in the Great Basin resulting from prior subduction and in the area of Yellowstone associated with the hot spot, and resistive areas to the east corresponding to the older and more stable cratons. Our results agree well with other publications which furthers the confidence in the inversion of the EarthScope MT project.

The magnetotelluric (MT) data collected as a part of the EarthScope project provided a unique opportunity to study the conductivity structure of the deep interior of the North American continent. Besides the scientific value of the recovered subsurface models, the data also allowed inversion practitioners to test the robustness of their algorithms applied to regional long-period data. In this paper, we present the results of MT inversion of a subset of the second footprint of the MT data collection covering the East Central United States. Our inversion algorithm implements simultaneous inversion of the full MT impedance data both for the 3-D conductivity distribution and for the distortion matrix. The distortion matrix provides the means to account for the effect of the near-surface geoelectrical inhomogeneities on the MT data. The long-period data do not have the resolution for the small near-surface conductivity anomalies, which makes an application of the distortion matrix especially appropriate. The determined conductivity model of the region agrees well with the known geologic and tectonic features of the East Central United States. The conductivity anomalies recovered by our inversion indicate a possible presence of the hot spot track in the area.

One of the most widely used inversion methods in geophysics is a Gauss-Newton algorithm. However, storage and inversion of the Hessian matrix in the model space is computationally expensive. At the same time, the size of the Hessian matrix in the data space can be managed on a workstation for a typical geophysical inverse problem. We have derived a regularized Gauss-Newton (RGN) algorithm in the data space and applied it to a magnetotelluric inverse problem. RGN inversion method was also compared with the preconditioned regularized conjugate gradient (RCG) algorithm. The results of the RGN inversion of MT data collected in the Pavant Butte hydrothermal area indicate that MT sounding represents a valuable method in hydrothermal exploration. Presentation Date: Tuesday, September 26, 2017 Start Time: 1:50 PM Location: 362A Presentation Type: ORAL

One of the major problems in the modeling and inversion of marine controlled-source electromagnetic (CSEM) data is related to the need for accurate representation of very complex geoelectrical models typical for marine environment. At the same time, the corresponding forward-modeling algorithms should be powerful and fast enough to be suitable for repeated use in hundreds of iterations of the inversion and for multiple transmitter/receiver positions. To this end, we have developed a novel 3D modeling and inversion approach, which combines the advantages of the finite-difference (FD) and integral-equation (IE) methods. In the framework of this approach, we have solved Maxwell’s equations for anomalous electric fields using the FD approximation on a staggered grid. Once the unknown electric fields in the computation domain of the FD method are computed, the electric and magnetic fields at the receivers are calculated using the IE method with the corresponding Green’s tensor for the background conductivity model. This approach makes it possible to compute the fields at the receivers accurately without the need of very fine FD discretization in the vicinity of the receivers and sources and without the need for numerical differentiation and interpolation. We have also developed an algorithm for 3D inversion based on the hybrid FD-IE method. In the case of the marine CSEM problem with multiple transmitters and receivers, the forward modeling and the Fréchet derivative calculations are very time consuming and require using large memory to store the intermediate results. To overcome those problems, we have applied the moving sensitivity domain approach to our inversion. A case study for the 3D inversion of towed streamer EM data collected by PGS over the Troll field in the North Sea demonstrated the effectiveness of the developed hybrid method.

Summary This paper demonstrates that the generalized effective-medium theory of induced polarization (GEMTIP) can properly represent the induced polarization (IP) phenomenon in the rock samples collected from submarine hydrothermal deposit. The QEMSCAN mineralogical analysis is deployed in order to clarify the contents of minerals in the rock samples. The results of complex resistivity (CR) measurements show that the rock samples can produce strong IP effect, as expected from QEMSCAN results. The CR data are inverted for GEMTIP model parameters taking into account the results of the QEMSCAN analysis. The inversion algorithm is based on the hybrid method using the genetic algorithm with simulated annealing and the regularized conjugate gradient method (SAAGA-CG). The inversion results demonstrate that the GEMTIP model describes the measured CR data well, and represents the IP effect properly. These results open a possibility to discriminate the minerals by GEMTIP model parameters, because GEMTIP model parameters recovered from the inversion are different for different minerals. It is recommended that the IP effect has to be taken into account in interpretation of the marine electromagnetic data.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2015GEMTIP inversion of complex resistivity data using a hybrid method based on a genetic algorithm with simulated annealing and regularized conjugate gradient methodAuthors: Wei Lin*Michael S. ZhdanovVladimir BurtmanAlex GribenkoWei Lin*University of Utah and TechnoImagingSearch for more papers by this author, Michael S. ZhdanovUniversity of Utah and TechnoImagingSearch for more papers by this author, Vladimir BurtmanUniversity of Utah and TechnoImagingSearch for more papers by this author, and Alex GribenkoUniversity of Utah and TechnoImagingSearch for more papers by this authorhttps://doi.org/10.1190/segam2015-5849506.1 SectionsSupplemental MaterialAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract This paper demonstrates that an ellipsoidal model of the generalized effective-medium theory of induced polarization (GEMTIP) can be used to effectively invert complex resistivity (CR) data into petrophysical parameters of rocks, including matrix resistivity, volume fraction, etc. The inversion of the CR data has proven to be very challenging due to the nonuniqueness and instability of this problem. This paper introduces a new hybrid method based on a genetic algorithm with simulated annealing and regularized conjugate gradient minimization (SAAGARCG). This fast and effective approach combines the advantages of both the SAAGA and RCG methods and converges into the global minimum. The case study presents the results of inversion of the observed CR data and their comparison with a QEMSCAN analysis for representative mineral rock samples. Keywords: algorithm, inversion, induced polarizationPermalink: https://doi.org/10.1190/segam2015-5849506.1FiguresReferencesRelatedDetailsCited byMultiscale nonlinear inversion of gravity data for depth-to-basement estimation via coupled stochastic-deterministic optimizationAli Jamasb, Seyed-Hani Motavalli-Anbaran, Vahid Entezar-Saadat, and Hermann Zeyen29 September 2021 | GEOPHYSICS, Vol. 86, No. 6Modifying the generalized effective-medium theory of induced polarization model in compacted rocksTong Xiaolong, Yan Liangjun, and Xiang Kui15 June 2020 | GEOPHYSICS, Vol. 85, No. 4Complex resistivity of mineral rocks in the context of the generalised effective-medium theory of the induced polarisation effect8 February 2018 | Geophysical Prospecting, Vol. 66, No. 4Effective-medium modeling of the induced-polarization effect in multiphase artificial mineral rocksWei Lin, Vladimir Burtman, Michael Zhdanov, Masashi Endo, and Shinichi Takakura1 September 2016Complex resistivity of mineral rocks in the context of the generalized effective-medium theory of the IP effectVladimir Burtman, Michael Zhdanov, Wei Lin, and Masashi Endo1 September 2016Mining and Geothermal Complete Session1 September 2016 SEG Technical Program Expanded Abstracts 2015ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2015 Pages: 5634 publication data© 2015 Published in electronic format with permission by the Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 19 Aug 2015 CITATION INFORMATION Wei Lin*, Michael S. Zhdanov, Vladimir Burtman, and Alex Gribenko, (2015), "GEMTIP inversion of complex resistivity data using a hybrid method based on a genetic algorithm with simulated annealing and regularized conjugate gradient method," SEG Technical Program Expanded Abstracts : 952-956. https://doi.org/10.1190/segam2015-5849506.1 Plain-Language Summary Keywordsalgorithminversioninduced polarizationPDF DownloadLoading ...

PreviousNext No AccessSEG Technical Program Expanded Abstracts 20153D inversion of regional MT data distorted by near-surface inhomogeneities using a complex distortion matrixAuthors: Alexander Gribenko*Michael S. ZhdanovAlexander Gribenko*University of Utah, TechnoImaging, and MIPTSearch for more papers by this author and Michael S. ZhdanovUniversity of Utah, TechnoImaging, and MIPTSearch for more papers by this authorhttps://doi.org/10.1190/segam2015-5821800.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract The distortion of regional electric fields by local structures represents one of the major problems facing three-dimensional magnetotelluric (MT) interpretation. The effect of 3D local inhomogeneities on MT data can be described by a distortion matrix. In this paper, we develop a method for simultaneous inversion of the full MT impedance data for 3D conductivity distribution and for a distortion matrix with complex components. We use integral equations method for forward modeling. Tikhonov regularization is employed to solve the resulting inverse problem. Minimization of the parametric functional is achieved via a conjugate gradient method. The inversion algorithm was tested on the synthetic data from Dublin Secret Model II (DSM 2), for which multiple inversion solutions are available for comparison. We also investigate a possibility of using the developed approach for corrections to the effect of topography on the MT data. Finally, the results are presented of an application of the inversion to a regional MT dataset acquired as part of the EarthScope project over the Great Basin region of the Western United States. Keywords: 3D, magnetotelluric, inversionPermalink: https://doi.org/10.1190/segam2015-5821800.1FiguresReferencesRelatedDetailsCited byLarge-Scale Inversion of Magnetotelluric Data Using Regularized Gauss–Newton Method in the Data Space21 September 2022 | Pure and Applied Geophysics, Vol. 179, No. 103D inversion of magnetotelluric data by using a hybrid forward-modeling approach and mesh decouplingDeniz Varılsüha11 September 2020 | GEOPHYSICS, Vol. 85, No. 5Joint 3D inversion of gravity and MT data using Gramian constraints: A case study from YellowstoneMichael Jorgensen and Michael S. Zhdanov27 August 20183-D Inversion of the MT EarthScope Data, Collected Over the East Central United States8 December 2017 | Geophysical Research Letters, Vol. 44, No. 23Regularized Gauss-Newton method of nonlinear geophysical inversion in the data space: Applications to 3D magnetotelluric inversionAlexander Gribenko and Michael Zhdanov17 August 2017EM Exploration Complete Session17 August 2017 SEG Technical Program Expanded Abstracts 2015ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2015 Pages: 5634 publication data© 2015 Published in electronic format with permission by the Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 19 Aug 2015 CITATION INFORMATION Alexander Gribenko* and Michael S. Zhdanov, (2015), "3D inversion of regional MT data distorted by near-surface inhomogeneities using a complex distortion matrix," SEG Technical Program Expanded Abstracts : 984-989. https://doi.org/10.1190/segam2015-5821800.1 Plain-Language Summary Keywords3DmagnetotelluricinversionPDF DownloadLoading ...