We have developed a feasibility study on the application of time-lapse gravity as a monitoring tool for a proposed [Formula: see text] sequestration test site. The results are a component of a larger geotechnical suitability study to evaluate a specific field’s potential for [Formula: see text] storage and to evaluate viable techniques for effective monitoring there. The reservoir model for this study was constructed from detailed reservoir data available through separate reservoir characterization studies of the field. The gravity inversion used was a highly constrained binary approach that incorporated reservoir geometry from seismic data and the internal 3D distributions of density change predicted from the reservoir engineering database. Incorporating borehole data for joint surface/borehole monitoring further improved the potential of time-lapse gravity to define [Formula: see text] movement during sequestration. In this paper, we present a subset of the entire study. Our results indicate that the site likely has a favorable combination of geometry, depth, thickness, and predicted density change from [Formula: see text] movement to be effectively monitored with surface time-lapse gravity.

Analysis of a current offshore prospect employed 3D numerical modeling of a controlled-source electromagnetic (CSEM) exploration system. The analysis considers the sensitivity of data presentations to assumptions about the background model. The numerical simulations show that false anomalies and significant distortion to anomaly magnitude can be caused by normalization of the observed electric fields by reference fields calculated from an incorrect or oversimplified background model. Bathymetry effects on the measured electric fields, if not accounted for, can produce anomalies as large as those of target sands. The maximum sensitivity to oil-water contacts or other strong lateral variations within the modeled channel sands is achieved by profiling along the length of the channel. Profiles run offset from a simulated oil-water contact by as little as [Formula: see text] show a response below the expected noise levels. Good background models can be constructed by taking advantage of the magnetotelluric data recorded by marine receivers during times when the CSEM transmitter is not in operation. The effects of electrical anisotropy can produce anomalies as large as target responses, although the spatial pattern of sheetlike anisotropic zones can be distinguished from the spatial pattern of sand-channel anomalies.

We describe the application of a 2D-constrained grid Euler deconvolution method which is able to determine for each solution window whether the source structure is two dimensional, three dimensional, or poorly defined and to estimate the source location and depth. In each solution window, eigenvalues and eigenvectors are derived from the Euler equations and compared to threshold levels. A single eigenvalue below the given threshold and lying in the x–y-plane is shown to indicate a 2D source, while the absence of such an eigenvalue indicates a 3D source geometry. Two small eigenvalues indicate the field in the window has no distinct source. Applying these criteria to each solution window allows us to generate a map of source-geometry distribution. We evaluate the effectiveness of 2D-constrained grid Euler deconvolution using synthetic magnetic data generated from a 3D basement model based on real topography from an area with surface-exposed faulting. This modeling strategy provides a complex, nonidealized data set that compares Euler depth estimates directly to the known basement surface depth. Our results indicate that noninteger structural indices can be the most appropriate choice for some data sets, and the 2D-constrained grid Euler method images magnetic basement structure more clearly and unambiguously than the conventional grid Euler method.

We propose an improved magnetic basement depth estimator using a hybrid of two Extended Euler methods. We test the method on the realistic Bishop model. In a significant advance on previous practice, we estimate basement depths independent of any structural index assumptions. We derive structural indices separately. The derived depths follow the general depth trends of the model with some discrepancies which are beyond the capabilities of magnetic depth estimation methods.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2004Testing magnetic local wavenumber depth estimation methods using a complex 3D test modelAuthors: J. D. FairheadS. E. WilliamsG. FlanaganJ. D. Fairhead, S. E. WilliamsSchool of Earth Sciences, University of Leeds, LS2 9JT, UK, and G. FlanaganRegional Gravity and Magnetics, ConocoPhillips, 3020 Permian Building, 600 North Dairy Ashford, Houston, TX 77079https://doi.org/10.1190/1.1851313 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Permalink: https://doi.org/10.1190/1.1851313FiguresReferencesRelatedDetailsCited byEuler solution selecting method based on the damping factor30 May 2022 | Acta Geophysica, Vol. 70, No. 4Transformation of magnetic data to the pole and vertical dip and a related apparent susceptibility transform: Exact and approximate approachesRichard S. Smith, Eric A. Roots, and Rajesh Vavavur24 January 2022 | GEOPHYSICS, Vol. 87, No. 2Multiscale 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. 6Use of the airborne magnetic data for edge basalt detection in Qaret Had El Bahr area, Northeastern Bahariya Oasis, Egypt24 May 2020 | Bulletin of Engineering Geology and the Environment, Vol. 79, No. 9Delineating flood hazards using the interpreted structural setting and GIS in Attaif, western Saudi Arabia28 February 2020 | Arabian Journal of Geosciences, Vol. 13, No. 5Geophysical study of Ubiaja and Illushi area in northern Anambra basin, Nigeria, using combined interpretation methods of aeromagnetic data6 April 2019 | Modeling Earth Systems and Environment, Vol. 5, No. 32D discrete wavelet transform for denoising aeromagnetic dataFelipe F. Melo, Valéria C. F. Barbosa, and Yolanda Jiménez-Teja27 August 2018Inferring the Subsurface Basement Depth and the Contact Locations from Aeromagnetic Data over Loum-Minta Area (Centre-East Cameroon)International Journal of Geosciences, Vol. 09, No. 07Practical considerations in the use of edge detectors for geologic mapping using magnetic dataMark Pilkington and Victoria Tschirhart27 February 2017 | GEOPHYSICS, Vol. 82, No. 3Self-Constrained Euler Deconvolution Using Potential Field Data of Different Altitudes19 February 2016 | Pure and Applied Geophysics, Vol. 173, No. 6Mapping the depth to magnetic basement using inversion of pseudogravity: Application to the Bishop model and the Stord Basin, northern North SeaAhmed Salem, Chris Green, Samuel Cheyney, J. Derek Fairhead, Essam Aboud, and Simon Campbell21 March 2014 | Interpretation, Vol. 2, No. 2Interpretation of magnetic data using tilt-angle derivativesAhmed Salem, Simon Williams, Derek Fairhead, Richard Smith, and Dhananjay Ravat16 November 2007 | GEOPHYSICS, Vol. 73, No. 1Generalized magnetic tilt‐Euler deconvolutionAhmed Salem, Richard Smith, Simon Williams, Dhananjay Ravat, and Derek Fairhead14 September 2007Evaluating normalized magnetic derivatives for structural mappingJ. D. Fairhead and S. E. Williams6 October 2006Hybrid Euler magnetic basement depth estimation: Bishop 3D testsAlan Reid, Desmond FitzGerald, and Guy Flanagan7 December 2005 SEG Technical Program Expanded Abstracts 2004ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2004 Pages: 2586 publication data© 2004 Copyright © 2004 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 03 Jan 2005 CITATION INFORMATION J. D. Fairhead, S. E. Williams, and G. Flanagan, (2004), "Testing magnetic local wavenumber depth estimation methods using a complex 3D test model," SEG Technical Program Expanded Abstracts : 742-745. https://doi.org/10.1190/1.1851313 Plain-Language Summary PDF DownloadLoading ...

PreviousNext No AccessSEG Technical Program Expanded Abstracts 20043D numerical simulation of a deepwater EM exploration surveyAuthors: G. Michael HoverstenGregory A. NewmanNathan GeierGuy FlanaganG. Michael HoverstenLawrence Berkeley National LaboratorySearch for more papers by this author, Gregory A. NewmanLawrence Berkeley National LaboratorySearch for more papers by this author, Nathan GeierConocoPhillipsSearch for more papers by this author, and Guy FlanaganConocoPhillipsSearch for more papers by this authorhttps://doi.org/10.1190/1.1851304 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract An analysis of a current offshore prospect has been carried out using three‐dimensional numerical modeling of a controlled source electromagnetic (CSEM) exploration system. The analysis considers the sensitivity of data presentations to assumptions about the background model. The numerical simulations show that false anomalies and significant distortion to anomaly magnitude can be caused by normalization of the observed electric fields by fields calculated from an incorrect or oversimplified background model. Bathymetry effects on the measured electric fields can, if not accounted for, produce anomalies as large as those of target sands. Good background models can be constructed by taking advantage of the magnetotelluric data recorded by marine receivers during times when the CSEM transmitter is not in operation.Permalink: https://doi.org/10.1190/1.1851304FiguresReferencesRelatedDetailsCited By2.5-D modeling of cross-hole electromagnetic measurement by finite element method29 May 2008 | Petroleum Science, Vol. 5, No. 2MMT forward modeling for a layered earth with arbitrary anisotropyGEOPHYSICS, Vol. 71, No. 3 SEG Technical Program Expanded Abstracts 2004ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2004 Pages: 2586 publication data© 2004 Copyright © 2004 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished: 03 Jan 2005 CITATION INFORMATION G. Michael Hoversten, Gregory A. Newman, Nathan Geier, and Guy Flanagan, (2004), "3D numerical simulation of a deepwater EM exploration survey," SEG Technical Program Expanded Abstracts : 672-675. https://doi.org/10.1190/1.1851304 Plain-Language Summary PDF DownloadLoading ...

Mushayandebvu et al. (2001) introduced a second equation, described as a rotational constraint. The profile based method is known as profile ‘extended Euler’ where is assumed zero in the above equation. For each operator window along a profile the solution location derived from the second equation is compared to that derived from conventional Euler and only solutions having similar locations are accepted, The accepted solutions are well resolved 2D source structures and give spatially more consistent results than conventional 2D Euler. A further advantage of this method is that dip and susceptibility contrast can be determined for contacts and dyke models. Extended Euler was then applied to grid data by Mushayandebvu et al. (2000). y T/∂ ∂

One of the hottest topics in seismic depth imaging these days is gravity modeling. What? That's right, most major oil companies and many smaller ones routinely integrate rigorous gravity models with their seismic depth migration workflow. If you think about it, it makes sense. Gravity data have always been effective at predicting the distribution of mass in the subsurface. Although once thought limited in resolution, gravity has gained new respect in the last five years due to careful modeling and thoughtful integration into the workflow of seismic depth migration.

A concerted effort is underway to prepare a substantially upgraded digital gravity anomaly database for the United States and to make this data set and associated usage tools available on the internet. This joint effort, spearheaded by the geophysics groups at the National Imagery and Mapping Agency (NIMA), University of Texas at El Paso (UTEP), U.S. Geological Survey (USGS), and National Oceanic and Atmospheric Administration (NOAA), is an outgrowth of the new geoscientific community initiative called Geoinformatics (www.geoinformaticsnetwork.org). This dominantly geospatial initiative reflects the realization by Earth scientists that existing information systems and techniques are inadequate to address the many complex scientific and societal issues. Currently, inadequate standardization and chaotic distribution of geoscience data, inadequate accompanying documentation, and the lack of easy-to-use access tools and computer codes for analysis are major obstacles for scientists, government agencies, and educators. An example of the type of activities envisioned, within the context of Geoinformatics, is the construction, maintenance, and growth of a public domain gravity database and development of the software tools needed to access, implement, and expand it. This product is far more than a high quality database; it is a complete data system for a specific type of geophysical measurement that includes, for example, tools to manipulate the data and tutorials to understand and properly utilize the data. On August 9, 2002, twenty-one scientists from the federal, private and academic sectors met at a workshop to discuss the rationale for upgrading both the United States and North American gravity databases (including offshore regions) and, more importantly, to begin developing an operational plan to effectively create a new gravity data system. We encourage anyone interested in contributing data or participating in this effort to contact G.R. Keller or T.G. Hildenbrand. This workshop was the first step in building a web-based data system for sharing quality gravity data and methodology, and it builds on existing collaborative efforts. This compilation effort will result in significant additions to and major refinement of the U.S. database that is currently released publicly by NOAA's National Geophysical Data Center and will also include an additional objective to substantially upgrade the North American database, released over 15 years ago (Committee for the Gravity Anomaly Map of North America, 1987).

Aeromagnetic data over the Mount Hood area of Oregon are dominated by the topographic expression of highly magnetized Cenozoic volcanics. Three‐dimensional magnetic modeling of the Mount Hood volcanic cone indicates that the bulk of the cone, above approximately 1650 m elevation, is composed of magnetically similar andesites. The andesites are magnetized in a normally polarized direction (I = 80.0°, D = 28.3°) and with a magnetization of 2.9 A/m. The chief exception to this is the possible remains of an old cone which underlies the northwest slope of the Mount Hood cone. Calculations show that this old cone is magnetized with a direction approximately opposite to the earth's present field and with a magnitude of magnetization of 3.9 A/m.