Structural/stratigraphic seismic images, obtained by seismic migrations applied in complex geological areas with restricted acquisition coverage and frequency band, are normally blurred, containing migration artifacts that limit the interpretation of target geological features. Data and Image-domains Least-Squares Migrations (LSM) (e.g., Fletcher et al., 2016) are routinely applied to overcome these challenges, yielding enhanced (de-blurred) images. Image-domain LSM methods are more efficient than data-domain methods, and they are normally based on the application of Point Spread Functions (PSFs) (e.g., Lecomte, 2008) computed on sparse spatial locations (avoiding interference among the PSFs). This work proposes an innovative PSF-driven LSM method based on the local angle domain (LAD) imaging system (Koren and Ravve, 2011). It inherently provides the (available) rich in-situ incident/scattered (I/S) illumination vectors which are further used to construct high-resolution PSF operators at each image grid point. The PSFs are then used as deconvolution operators to enhance the migration image. We demonstrate the imaging enhancements provided by the proposed LAD-PSF LSM approach on real data.

Using land seismic data from the Eagle Ford Play, we present an efficient workflow for accurately determining the subsurface Q-factor model, mainly accounting for local viscoelastic effects. The method is primarily based on an advanced Q seismic migration that makes it possible to create amplitude/phase preserved, full-azimuth, angle domain common image gathers. The obtained image gathers are then directly used as input to a novel Q-Tomography, formulated with a unique source consistency objective function that yields stable inverted parameters. We analyze the feasibility and plausibility of the inverted Q field and demonstrate its contribution for improving the quality of the seismic image gathers and the final seismic image.

One of the main challenges in seismic imaging, especially of land data, is building the near surface velocity model, as it is normally characterized by very low velocity values with different types of local anomalies. Resolving the near surface velocity model using only refraction data (e.g., refraction tomography) is insufficient, as it does not provide the required lateral resolution. Using only reflection data is equally insufficient, as it does not provide the required vertical resolution. We present a tomographic approach for simultaneously resolving the shallow and deep subsurface anisotropic velocity fields, where we jointly utilize both reflection and refraction data. By constructing a constrained joint reflection-refraction objective function, we show that this tomography can provide high-resolution anisotropic velocity models and subsequent accurate depth migration images. The method has been successfully applied to a 3D dataset from the Eagle Ford play in south central Texas. The results demonstrate that the method produces a very accurate near surface anisotropic velocity model.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2020Using principal component analysis to decouple seismic diffractions from specular reflectionsAuthors: Raanan DafniRina SchwartzRonit LevyZvi KorenRaanan DafniEmersonSearch for more papers by this author, Rina SchwartzEmersonSearch for more papers by this author, Ronit LevyEmersonSearch for more papers by this author, and Zvi KorenEmersonSearch for more papers by this authorhttps://doi.org/10.1190/segam2020-3421255.1 SectionsSupplemental MaterialAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail AbstractMethods developed for diffraction imaging are commonly based on a separation technique between continuous and discontinuous structural elements, based on their seismic response. Seismic imaging in the dip-angle domain decomposes direction-dependent images where the response of different structural elements is clearly distinguished. The subsurface structural geometry dictates a local dip-angle seismic signature of preferable scattering directions, accordingly. Assuming these signatures are uncorrelated, we propose a practical workflow for dip-angle domain principal component analysis as a comprehensive structural feature separator. Once the dip-angle images are transformed into their principal components, a back projection yields structural-specific images of the subsurface main building blocks. Our proposal emphasizes the strength of principal component analysis as a producer of probable geologic features from pre-stack dip-angle data. These should be incorporated as structural attributes to enhance seismic interpretation, reduce uncertainty and enable automation.Presentation Date: Wednesday, October 14, 2020Session Start Time: 1:50 PMPresentation Time: 3:55 PMLocation: 362DPresentation Type: OralKeywords: diffraction, common angle, interpretation, prestack, seismic attributesPermalink: https://doi.org/10.1190/segam2020-3421255.1FiguresReferencesRelatedDetailsCited bySeismic lineaments characterization using independent component analysisAbdulmohsen AlAli, Yazeed Altowairqi, Constantinos Tsingas, and Ali AlSultan15 August 2022 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 Raanan Dafni, Rina Schwartz, Ronit Levy, and Zvi Koren, (2020), "Using principal component analysis to decouple seismic diffractions from specular reflections," SEG Technical Program Expanded Abstracts : 2958-2962. https://doi.org/10.1190/segam2020-3421255.1 Plain-Language Summary Keywordsdiffractioncommon angleinterpretationprestackseismic attributesPDF DownloadLoading ...

Summary We present an efficient and stable procedure for estimating second- and fourth-order azimuthally-dependent effective parameters from full-azimuth residual moveouts. The residual moveouts are automatically picked at depth image points along full-azimuth angle domain reflection angle gathers. It is assumed that the azimuthally varying residual moveouts are due to fracture systems within compacted sand/shale sediment layers which were not accounted for in the seismic migration. The extracted (up to eight) effective parameters can then be used to obtain local (layer) effective parameters, characterizing the intensity and orientation of the fracture systems at each layer. Finally, the local effective parameters can be inverted to obtain interval anisotropic (e.g., orthorhombic) model parameters to be used in orthorhombic seismic migration.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2013Conversion of background VTI depth model and full azimuth reflection angle moveouts into interval orthorhombic and/or TTI layered parametersAuthors: Zvi KorenIgor RavveRonit LevyZvi KorenParadigm GeophysicalSearch for more papers by this author, Igor RavveParadigm GeophysicalSearch for more papers by this author, and Ronit LevyParadigm GeophysicalSearch for more papers by this authorhttps://doi.org/10.1190/segam2013-0172.1 SectionsSupplemental MaterialAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract We consider a case where full-azimuth reflection angle gathers were generated using a background VTI depth model. Residual moveouts (RMO) which were automatically picked on these 3D gathers along major horizons indicate considerable periodic azimuthal variations. Our aim is to use the azimuthally dependent RMOs in order to convert the background VTI model into interval TTI and/or orthorhombic layer parameters. Our method is based on a newly derived generalized Dix-based theory, assuming a locally varying 1D TTI, orthorhombic or mixed model, where at each location the vertical orthorhombic axis is the same for all layers but the azimuthal orientations of TTI and orthorhombic layers are different. An effective model for such a layered structure represents a single layer with identical vertical time, effective fast and slow NMO velocities and effective azimuthal orientation of the slow NMO velocity. The NMO velocity and the surface offset azimuth of the effective model coincide with the parameters of the original package of layers for any azimuth of the phase velocity. Our approach starts with a Fourier-based conversion of the RMOs into azimuthally dependent NMO velocities, which are then inverted into three local effective parameters. Finally, we apply a generalized Dix-based inversion approach to estimate the interval orthorhombic or TTI parameters within each layer. Permalink: https://doi.org/10.1190/segam2013-0172.1FiguresReferencesRelatedDetailsCited ByFourth-order NMO velocity for P-waves in layered orthorhombic media vs phase azimuthIgor Ravve and Zvi Koren1 September 2016Azimuthally dependent anisotropic velocity model updateGEOPHYSICS, Vol. 79, No. 2 SEG Technical Program Expanded Abstracts 2013ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2013 Pages: 5258 Publisher:Society of Exploration Geophysicists HistoryPublished: 19 Aug 2013 CITATION INFORMATION Zvi Koren, Igor Ravve, and Ronit Levy, (2013), "Conversion of background VTI depth model and full azimuth reflection angle moveouts into interval orthorhombic and/or TTI layered parameters," SEG Technical Program Expanded Abstracts : 3068-3072. https://doi.org/10.1190/segam2013-0172.1 Plain-Language Summary PDF DownloadLoading ...

ABSTRACTWe use residual moveouts measured along continuous full azimuth reflection angle gathers, in order to obtain effective horizontal transversely isotropic model parameters. The angle gathers are generated through a special angle domain imaging system, for a wide range of reflection angles and full range of phase velocity azimuths. The estimation of the effective model parameters is performed in two stages. First, the background horizontal transversely isotropic (HTI)/vertical transversely isotropic (VTI) layered model is used, along with the values of reflection angles, for converting the measured residual moveouts (or traveltime errors) into azimuthally dependent normal moveout (NMO) velocities. Then we apply a digital Fourier transform to convert the NMO velocities into azimuthal wavenumber domain, in order to obtain the effective HTI model parameters: vertical time, vertical compression velocity, Thomsen parameter delta and the azimuth of the medium axis of symmetry. The method also provides a reliability criterion of the HTI assumption. The criterion shows whether the medium possesses the HTI type of symmetry, or whether the azimuthal dependence of the residual traveltime indicates to a more complex azimuthal anisotropy. The effective model used in this approach is defined for a 1D structure with a set of HTI, VTI and isotropic layers (with at least one HTI layer). We describe and analyse the reduction of a multi‐layer structure into an equivalent effective HTI model. The equivalent model yields the same NMO velocity and the same offset azimuth on the Earth's surface as the original layered structure, for any azimuth of the phase velocity. The effective model approximates the kinematics of an HTI/VTI layered structure using only a few parameters. Under the hyperbolic approximation, the proposed effective model is exact.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2009Effective model for HTI / VTI layered mediaAuthors: Zvi KorenIgor RaweRonit LevyZvi KorenParadigm Geophysical SummarySearch for more papers by this author, Igor RaweParadigm Geophysical SummarySearch for more papers by this author, and Ronit LevyParadigm Geophysical SummarySearch for more papers by this authorhttps://doi.org/10.1190/1.3255447 SectionsSupplemental MaterialAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract The simplest assumption on an anisotropic medium with azimuthally dependent traveltime is an HTI. We use residual moveouts measured along continuous full azimuth reflection angle gathers, in order to obtain effective HTI model parameters. The angle gathers are generated through a special angle domain imaging system, for a wide range of reflection angles and full range of phase velocity azimuths. The estimation of the effective model parameters is performed in two stages. First, the background HTI/VTI layered model is used, along with the values of reflection angles, for converting the measured residual moveouts (or traveltime errors) into azimuthally dependent NMO velocities. Then, we apply a Fourier transform to convert the NMO velocities into azimuthal wavenumber domain, in order to obtain the effective HTI model parameters: vertical time, vertical compression velocity, Thomsen parameter delta, and the azimuth of the medium axis of symmetry. The method also provides a reliability criterion of the HTI assumption. The effective model used in this approach is defined for a 1D model with a set of HTI, VTI, and isotropic layers. We describe and analyze the reduction of a multi‐layer structure into an equivalent effective HTI model. The equivalent model yields the same NMO velocity and the same offset azimuth on the earth surface as the original layered structure, for any azimuth of the phase velocity. The effective model approximates the kinematics of an HTI/VTI layered structure using only a few parameters. Under the hyperbolic approximation, the proposed effective model is exact.Permalink: https://doi.org/10.1190/1.3255447FiguresReferencesRelatedDetails SEG Technical Program Expanded Abstracts 2009ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2009 Pages: 4338 publication data© 2009 Copyright © 2009 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished: 14 Oct 2009 CITATION INFORMATION Zvi Koren, Igor Rawe, and Ronit Levy, (2009), "Effective model for HTI / VTI layered media," SEG Technical Program Expanded Abstracts : 286-290. https://doi.org/10.1190/1.3255447 Plain-Language Summary PDF DownloadLoading ...