Dixie Valley, located in west-central Nevada within the Basin and Range Province, is one of the most important geothermal systems in the western United States and an increasingly attractive target for critical-mineral exploration. The valley combines active extensional tectonics, major range-front and intrabasin fault systems, high heat flow, hydrothermal alteration, and thick sedimentary basins that may provide favorable conditions for the development of geothermal reservoirs and lithium-bearing brines or clays. This paper presents an integrated multiphysics interpretation of gravity, magnetic, helicopter-borne time-domain electromagnetic (HeliTEM), and magnetotelluric (MT) data from Dixie Valley, with emphasis on the Grover Point area investigated by the Basin and Range Investigation for Developing Geothermal Energy (BRIDGE) program. We apply joint Gramian inversion of gravity and magnetic data to recover mutually consistent density and magnetization models, including separate induced and remanent magnetization components. We also perform rigorous 3D inversion of HeliTEM data and cooperative 3D inversion of HeliTEM and MT data to obtain a resistivity model extending from the shallow basin fill to deeper fault-controlled geothermal structures. The integrated interpretation identifies low-density sedimentary basins, induced magnetization highs related to magnetic basement or intrusive rocks, remanent magnetization variations associated with basement architecture and hydrothermal alteration, and conductive corridors interpreted as clay-rich alteration zones and possible hydrothermal pathways. These results demonstrate that integrated gravity, magnetic, HeliTEM, and MT inversion can substantially reduce interpretation ambiguity and improve targeting of concealed geothermal systems and associated lithium resources in extensional terranes.

We present an integrated methodology for three-dimensional inversion of large-scale airborne electromagnetic (AEM) and magnetic survey data that simultaneously recovers electrical conductivity, chargeability, and both induced and remanent magnetizations. A central feature of the AEM component is the explicit incorporation of induced polarization (IP) effects. Neglecting IP responses can lead to biased conductivity models, particularly in mineralized systems where disseminated sulfides contribute strongly to chargeability. Using the Generalized Effective-Medium Theory of Induced Polarization (GEMTIP), the inversion produces physically consistent 3D distributions of conductivity and chargeability. To enhance magnetic interpretation, we also implement a vector magnetic inversion that resolves both induced and remanent magnetization from Total Magnetic Intensity (TMI) data, enabling geologically realistic magnetization models in terranes with significant remanence. This integrated workflow was applied to airborne AEM and TMI datasets collected over the Asankrangwa Gold Belt in central Ghana. The inversion results delineate a key exploration target defined by coincident magnetic low and elevated chargeability, interpreted as sulfide-rich gold mineralization and subsequently confirmed by drilling. These results demonstrate that jointly accounting for IP and remanent magnetization in 3D inversion substantially improves subsurface characterization and provides a powerful tool for mineral exploration in structurally and lithologically complex environments.

The ability to monitor reservoir behavior over the course of production is necessary for optimization of production performance and the development of production strategies. This goal can be achieved by geophysical monitoring of the fluid propagation within the reservoir. Electromagnetic methods represent an important technique for geophysical monitoring of reservoirs, because they can distinguish between hydrocarbons and saline water based on their differing resistivities. The induced polarization (IP) method can be used to detect additional electrical property contrasts between the fluids and thus can increase the method's sensitivity to the differing fluids. This chapter considers an application of nanoparticles for reservoir monitoring in order to enhance the electrical conductivity contrast and the IP responses associated with the oil–water interface within the reservoir.

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.

This paper introduces an original approach to the joint inversion of airborne electromagnetic (EM) data for three-dimensional (3D) conductivity and chargeability models using hybrid finite difference (FD) and integral equation (IE) methods. The inversion produces a 3D model of physical parameters, which includes conductivity, chargeability, time constant, and relaxation coefficients. We present the underlying principles of this approach and an example of a high-resolution inversion of the data acquired by a new active time domain airborne EM system, TargetEM, in Ontario, Canada. The new TargetEM system collects high-quality multicomponent data with low noise, high power, and a small transmitter–receiver offset. This airborne system and the developed advanced inversion methodology represent a new effective method for mineral resource exploration.

This paper discusses the physical and mathematical principles of the airborne induced polarization (IP) method. The possibility of extracting information about the IP properties of rocks from airborne survey data has become a subject of active research recently. We introduce a method for the joint inversion of the airborne EM data into the electrical conductivity and IP parameters based on the generalized effective-medium theory of induced polarization (GEMTIP). We also present the results of the inversion of the airborne EM data collected over the Echum Project Area, in Northwestern Ontario, Canada, into 3D conductivity and chargeability models. Obtaining IP physical property models from an airborne geophysical survey may result in a paradigm change in mineral exploration by pulling more information and value from airborne EM surveys.

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.

The Saudi Arabian Glass Earth Pilot Project is a geophysical exploration program to explore the upper crust of the Kingdom for minerals, groundwater, and geothermal resources as well as strictly academic investigations. The project began with over 8000 km2 of green-field area. Airborne geophysics including electromagnetic (EM), magnetics, and gravity were used to develop several high priority targets for ground follow-up. Based on the results of airborne survey, a spectral induced polarization (SIP) survey was completed over one of the prospective targets. The field data were collected with a distributed array system, which has the potential for strong inductive coupling. This was examined in a synthetic study, and it was determined that with the geometries and conductivities in the field survey, the inductive coupling effect may be visible in the data. In this study, we also confirmed that time domain is vastly superior to frequency domain for avoiding inductive coupling, that measuring decays from 50 ms to 2 s allow discrimination of time constants from 1 ms to 5 s, and the relaxation parameter C is strongly coupled to intrinsic chargeability. We developed a method to fully include all 3D EM effects in the inversion of induced polarization (IP) data. The field SIP data were inverted using the generalized effective-medium theory of induced polarization (GEMTIP) in conjunction with an integral equation-based modeling and inversion methods. These methods can replicate all inductive coupling and EM effects, which removes one significant barrier to inversion of large bandwidth spectral IP data. The results of this inversion were interpreted and compared with results of drill hole set up in the survey area. The drill hole intersected significant mineralization which is currently being further investigated. The project can be considered a technical success, validating the methods and effective-medium inversion technique used for the project.

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 ...

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2020Joint inversion of airborne electromagnetic and total magnetic intensity data using Gramian structural constraints: Case study of the Reid-Mahaffy test site in Ontario, CanadaAuthors: Michael JorgensenLeif CoxMichael S. ZhdanovMichael JorgensenUniversity of Utah, and TechnoImagingSearch for more papers by this author, Leif CoxUniversity of Utah, and TechnoImagingSearch for more papers by this author, and Michael S. ZhdanovUniversity of Utah, and TechnoImagingSearch for more papers by this authorhttps://doi.org/10.1190/segam2020-3427220.1 SectionsSupplemental MaterialAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail AbstractAcquisition of airborne electromagnetic (AEM) data is usually combined with the total magnetic intensity (TMI) surveying, making these two geophysical methods a natural choice for joint inversion. In this paper, we present an algorithm for joint inversion of the frequency or time domain airborne electromagnetic (AEM) and TMI data producing structurally similar 3D conductivity and susceptibility models. The method is based on the structural Gramian constraints (Zhdanov et al., 2012; Zhdanov, 2015), which enforce structural correlations of the gradients of different physical property models. The method is illustrated by the results of inverting the frequency-domain DIGHEM AEM and airborne magnetic data collected over the Reid-Mahaffy test site in Ontario, Canada. By combining these complementary datasets, we produce subsurface images of geological structures with the sharper boundaries, stronger structural correlations, and with the same level of data misfit as the standalone inversions.Presentation Date: Wednesday, October 14, 2020Session Start Time: 9:20 AMPresentation Time: 9:20 AMLocation: Poster Station 7Presentation Type: PosterKeywords: airborne survey, electromagnetics, magnetics, inversionPermalink: https://doi.org/10.1190/segam2020-3427220.1FiguresReferencesRelatedDetails 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 Jorgensen, Leif Cox, and Michael S. Zhdanov, (2020), "Joint inversion of airborne electromagnetic and total magnetic intensity data using Gramian structural constraints: Case study of the Reid-Mahaffy test site in Ontario, Canada," SEG Technical Program Expanded Abstracts : 611-615. https://doi.org/10.1190/segam2020-3427220.1 Plain-Language Summary Keywordsairborne surveyelectromagneticsmagneticsinversionPDF DownloadLoading ...

Modern distributed DC/IP survey arrays can collect large amounts of broadband electrical data. These arrays are no longer limited to simple in-line dipole-dipole or pole-dipole surveys as they were in the past. This allows geophysicists to apply true 3D geometries and use arbitrary transmitter and receiver positions, which opens the door to high resolution 3D information about the spectral complex resistivity response of the earth and possibly mineral discrimination. However, these arrays also increase the computational complexity of solving the inverse problem for earth’s parameters. In addition, the increase in the frequency range of the collected data along with the complex wire paths raises the chances of incurring inductive coupling, which can hide the complex resistivity response. This paper examines the problems of inductive coupling in broadband, complex wire path surveys and finds that it can indeed affect the IP response. By using the full EM solution and known geometry of the wire paths, we can increase the usable IP data by about one decade of frequency or time measurements. We have modified an existing modeling and inversion code to handle the explicit geometry of the wire paths and to include the full EM effects, all in an efficient manner, which makes it possible to conduct a rigorous inversion of these 3D survey data. An inversion of the field data compares well with other information, demonstrating the effectiveness of the developed method. Presentation Date: Wednesday, September 18, 2019 Session Start Time: 1:50 PM Presentation Time: 3:30 PM Location: Poster Station 10 Presentation Type: Poster

The Saudi Arabian Glass Earth (Pilot) project is a geophysical exploration project to explore the upper crust of the Kingdom for minerals, groundwater, and geothermal resources as well as strictly academic investigations. The project began with over 8000 km2 of green fields area. Airborne geophysics including EM, magnetics, and gravity were used to develop several high priority targets for ground follow-up. Based on the results of airborne survey, a spectral induced polarization (SIP) survey was completed over one of the prospective targets. The field SIP data were inverted using the GEMTIP model in conjunction with an integral equation-based modeling and inversion code. This code can replicate all inductive coupling and EM effects, which removes one large barrier to inversion of large bandwidth spectral IP data. The results of this inversion were interpreted, and several drill holes sited. The drill holes intersected significant mineralization which is currently being further investigated. The project can be considered a technical success, validating the methods and effective-medium inversion technique used for the project. Presentation Date: Wednesday, September 18, 2019 Session Start Time: 1:50 PM Presentation Time: 3:05 PM Location: Poster Station 10 Presentation Type: Poster

Recent developments in large-scale geophysical inversions made it possible to invert the results of entire airborne geophysical surveys over large areas into 3D models of the subsurface. This paper presents the methods for and results of the interpretation of the data acquired by a multiphysics airborne geophysical survey in Saudi Arabia. The project involved the acquisition, processing, and interpretation of airborne electromagnetic, gravity, and magnetic geophysical data over an 8000 square kilometer area. All the collected data were carefully analyzed and inverted in 3D models of the corresponding physical properties of the subsurface, including 3D density, magnetization vector, and conductivity models. This paper summarizes the interpretation of all geophysical data sets collected during the field airborne survey. The goal of the paper is to demonstrate how the advanced 3D modeling and inversion methods can be effectively used for interpretation of multiphysics airborne survey data and to study and analyze the potential of the survey area for natural resource exploration in Saudi Arabia.

This paper develops a novel method of 3D inversion of induced polarization (IP) survey data, based on a generalized effective-medium model of the IP effect (GEMTIP). The electrical parameters of the effective-conductivity model are determined by the intrinsic petrophysical and geometrical characteristics of composite media, such as the mineralization and/or fluid content of rocks and the matrix composition, porosity, anisotropy, and polarizability of formations. The GEMTIP model of multiphase conductive media provides a quantitative tool for evaluation of the type of mineralization, and the volume content of different minerals using electromagnetic (EM) data. The developed method takes into account the nonlinear nature of both electromagnetic induction and IP phenomena and inverts the EM data in the parameters of the GEMTIP model. The goal of the inversion is to determine the electrical conductivity and the intrinsic chargeability distributions, as well as the other parameters of the relaxation model simultaneously. The recovered parameters of the relaxation model can be used for the discrimination of different rocks, and in this way may provide an ability to distinguish between uneconomic mineral deposits and zones of economic mineralization using geophysical remote sensing technology.

This paper presents the results of an application of the time domain electromagnetic (TDEM) method for the exploration of submarine hydrothermal deposits using the generalized effective-medium relaxation model of the IP effect (GEMTIP). The TDEM data were acquired by a specially developed marine TDEM data acquisition system. It is known that the hydrothermal deposits consist of massive sulfides and can produce strong IP effect. In order to take this effect into account in interpretation of the observed data, we assume that the resistivity is frequency dependent and can be characterized by the GEMTIP relaxation model, including the chargeability, the time constant, and the relaxation parameter. The high chargeability anomaly determined by the 3D GEMTIP inversion coincides with the known submarine hydrothermal deposit. This opens a possibility to explore the submarine hydrothermal deposits effectively by marine TDEM method with 3D GEMTIP inversion. Presentation Date: Wednesday, September 27, 2017 Start Time: 9:45 AM Location: 362A Presentation Type: ORAL

3D inversion of airborne electromagnetic data is a challenging task due to the large amounts of data collected over relatively large areas. In this paper we detail an inversion algorithm based on a moving sensitivity domain approach using the integral equation method coupled with a multistep regularized conjugate gradient inversion. To tackle the computational demands, along with the reduction of the problem due to the moving sensitivity domain approach, we also parallelize the problem over the data using Message Passing Interface (MPI) and OpenMP. The workflow of the interpretation includes 1D inversion to obtain a background structure that serves as an input to the 3D inversion. The background is either a half-space, unique under each data point, in the case of frequency domain, or layered background in the case of time domain inversion. We demonstrate the effectiveness of the developed method and computer software by 3D inversion examples of frequency and time domain airborne EM surveys. Presentation Date: Tuesday, October 18, 2016 Start Time: 1:25:00 PM Location: 174 Presentation Type: ORAL