Summary Over the years Shenzi field in deep-water Gulf of Mexico became a test bed for evaluation of new seismic acquisition and processing technologies. These include 3D narrow azimuth streamer data, 3D-rich azimuth streamer data, and recently 3D OBN data (Mifflin et al, 2021). On the processing side, many types of processing techniques were used to image the various data types recorded over Shenzi field, from 3D ray-based Kirchhoff summation PSDM to Acoustic RTM PSDM and Acoustic FWI imaging. In the work presented here we demonstrate the advantages of Full Elastic imaging using the OBN dataset acquired by Woodside Energy in 2019 to better image the sub-salt field.

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Seismic imaging has been continuously advancing since the early days of computer revolution in the 1970s. Practical imaging during this time was carried out only in two dimensions using simplified wave equations on poststack data. Subsequently, in the early 1980s algorithm improvements in wave equation migration after the introduction of one-way phase shift methods and two-way reverse time migration occurred. Concurrently, improvements in ray-based Kirchhoff migration emerged after the introduction of eikonal and wavefront reconstruction solvers for calculation of travel times. In the late 1980s, 3D prestack Kirchhoff migration began to be used.

With readily available wide-azimuth, onshore, 3D seismic data, the search for attributes utilizing the azimuthal information is ongoing. Theoretically, in the presence of ordered fracturing, the seismic wavefront shape changes from spherical to nonspherical with the propagation velocity being faster parallel to the fracturing and slower perpendicular to the fracture direction. This concept has been adopted and is used to map fracture direction and density within unconventional reservoirs. More specifically, azimuthal variations in normal moveout velocity or migration velocity are often used to infer natural fracture orientation. Analyses of recent results have called into question whether azimuthal velocity linked to intrinsic azimuthal velocity variations can actually be detected from seismic data. By use of 3D orthorhombic anisotropic elastic simulation, we test whether fracture orientation and intensity can be detected from seismic data. We construct two subsurface models based on interpreted subsurface layer structure of the Anadarko Basin in Oklahoma. For the first model, the material parameters in the layers are constant vertically transverse isotropic (VTI) in all intervals. The second model was constructed the same way as the base model for all layers above the Woodford Shale Formation. For the shale layer, orthorhombic properties were introduced. In addition, a thicker wedge layer was added below the shale layer. Using the constructed model, synthetic seismic data were produced by means of 3D anisotropic elastic simulation resulting in two data sets: VTI and orthorhombic. The simulated data set was depth migrated using the VTI subsurface model. After migration, the residual moveouts on the migrated gathers were analyzed. The analysis of the depth-migrated model data indicates that for the typical layer thicknesses of the Woodford Shale layer in the Anadarko Basin, observed and modeled percentage of anisotropy and target depth, the effect of intrinsic anisotropy is too small to be detected in real seismic data.

Depth imaging has long been a staple in offshore processing sequences; however, conventional wisdom often dictates that prestack depth migration is unnecessary in the onshore, geologically benign settings encountered in most unconventional shale reservoirs. Using examples from the Anadarko Basin, we demonstrate that careful depth imaging using updated processing flows yields significant benefits when compared to time imaging.

PreviousNext No Access15th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 31 July-3 August 2017Depth Imaging – More than PSDMAuthors: David KesslerDan KosloffJeff CoddAllon BartanaDavid KesslerSeismicCity Inc.Search for more papers by this author, Dan KosloffSeismicCity Inc.Search for more papers by this author, Jeff CoddSeismicCity Inc.Search for more papers by this author, and Allon BartanaSeismicCity Inc.Search for more papers by this authorhttps://doi.org/10.1190/sbgf2017-353 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract In principal, depth imaging refers to application of pre stack depth migration (i.e. PSDM). In practice, Depth Imaging grew to occupy a central role in almost all segments of seismic data processing and interpretation, both structural and quantitative. This presentation describes the various aspects of depth imaging technology. Today depth imaging covers the tasks of construction of anisotropic geological models, interpretation, final imaging, time to depth conversion, preparation of data for AVO analysis and impedance inversion, and simulation to assist geologists in the understanding of seismic data and in the design of seismic data acquisition. The evolution of depth imaging has erased the traditional distinction between data processing and interpretation. Today, the construction of a subsurface depth model involves the interpretation and success depends on constant and consistent geological input. Thus upon completion of a model building project, a large portion of the interpretation has been completed. Keywords: prestack, depth migration, imaging, inversionPermalink: https://doi.org/10.1190/sbgf2017-353FiguresReferencesRelatedDetailsCited bySeismic Modelling and Inversion25 June 2021 15th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 31 July-3 August 2017ISSN (online):2159-6832Copyright: 2017 Pages: 1876 publication data© 2017 Published in electronic format with permission by the Brazilian Geophysical SocietyPublisher:Society of Exploration Geophysicists HistoryPublished Online: 03 Aug 2017 CITATION INFORMATION David Kessler, Dan Kosloff, Jeff Codd, and Allon Bartana, (2017), "Depth Imaging – More than PSDM," SEG Global Meeting Abstracts : 1793-1795. https://doi.org/10.1190/sbgf2017-353 Plain-Language Summary Keywordsprestackdepth migrationimaginginversionPDF DownloadLoading ...

Drilling up-dip wells, in close proximity to salt bodies is common practice in exploration for oil and gas. Imaging of sand layers close to salt however is difficult in many cases owing to the complex geometrical shape of the salt body as well as the rapid change in material properties between the sedimentary section and the salt body. In many cases this results in either drilling into the salt body by mistake, or too low in the target formations. This difficulty is very well known in the Gulf of Mexico shelf which has been a prolific oil and gas producing region for more than 70 years. Over the years, seismic data used for interpretation and prospect generation in this area has been sub-optimal in many cases. Many of the producing fields in the Gulf of Mexico shelf consist of steeply dipping hydrocarbon-bearing sands truncated against salt domes. Unfortunately, in many cases the salt bodies defining the reservoir edges are not well imaged on associated seismic data, making the accurate mapping of the producing reservoir very difficult (Foley et. al., 1991). One solution to the seismic imaging problem can be achieved by design and acquisition of new seismic data. In the past few years, more effort has taken place to acquire new data on the Gulf of Mexico shelf, but dense spacing of surface platforms makes acquiring new surface streamer data difficult. The newer data is mainly acquired using ocean bottom node technology which results in wide azimuth seismic data. The new data has the potential to have much better seismic resolution than the older narrow azimuth streamer data used by the industry for many years. In addition, nodes can be placed much closer to surface installations creating better illumination in these areas. However, because of the complexity of the geology in close proximity to salt bodies, the clear imaging of sedimentary layers near salt remains challenging even when the newest seismic data is used.

The Gulf of Mexico shelf has been a prolific oil and gas production region for over seventy years. With limited ability to acquire new seismic streamer data due to dense surface platforms, seismic data used for interpretation and prospect generation has been in many cases sub-optimal. However, much advancement has been made in imaging technology that has enabled us to improve the interpretation and understanding of old producing fields.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2015GPU implementation of minimal dispersion recursive operators for reverse time migrationAuthors: Allon Bartana*Dan KosloffBrandon WarnellChris ConnorJeff CoddDavid KesslerPaulius MicikeviciusTy MckercherPeng WangPaul HolzhauerAllon Bartana*SeismicCity Inc.Search for more papers by this author, Dan KosloffSeismicCity Inc.Search for more papers by this author, Brandon WarnellSeismicCity Inc.Search for more papers by this author, Chris ConnorSeismicCity Inc.Search for more papers by this author, Jeff CoddSeismicCity Inc.Search for more papers by this author, David KesslerSeismicCity Inc.Search for more papers by this author, Paulius MicikeviciusNvidia CorporationSearch for more papers by this author, Ty MckercherNvidia CorporationSearch for more papers by this author, Peng WangNvidia CorporationSearch for more papers by this author, and Paul HolzhauerNvidia CorporationSearch for more papers by this authorhttps://doi.org/10.1190/segam2015-5754164.1 SectionsSupplemental MaterialAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract The implementation of new recursive operators for computation of numerical derivatives results in minimal dispersion in Reverse Time Migration Prestack Depth Migration (i.e. RTM PSDM). Compared to the more commonly used finite difference operators, the presented new method enables imaging of higher frequencies in RTM PSDM. Since RTM PSDM is the modern method of choice for imaging many exploration targets, computer optimization is an integral part of code development. We present here details of the GPU implementation for newly developed spatial derivative operators which enable routine use in industrial settings. Keywords: programming, parallel, optimization, algorithm, reverse time migrationPermalink: https://doi.org/10.1190/segam2015-5754164.1FiguresReferencesRelatedDetailsCited byUse of prestack depth migration for improving the accuracy of horizontal drilling in unconventional reservoirsMarianne Rauch-Davies, Scott Sutherland, Michael Bradshaw, Jeff Codd, and David Kessler29 December 2017 | The Leading Edge, Vol. 37, No. 1Accelerating Pre-stack Kirchhoff Time Migration by Manual Vectorization16 September 2016 | Concurrency and Computation: Practice and Experience, Vol. 29, No. 22A new time-space domain dispersion-relation-based implicit staggered-grid finite-difference scheme for scalar wave-equation modelingYaning Liu*, Wen Hu, and Chaoshun Hu1 September 2016Seismic Modeling 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 Allon Bartana*, Dan Kosloff, Brandon Warnell, Chris Connor, Jeff Codd, David Kessler, Paulius Micikevicius, Ty Mckercher, Peng Wang, and Paul Holzhauer, (2015), "GPU implementation of minimal dispersion recursive operators for reverse time migration," SEG Technical Program Expanded Abstracts : 4116-4120. https://doi.org/10.1190/segam2015-5754164.1 Plain-Language Summary Keywordsprogrammingparalleloptimizationalgorithmreverse time migrationPDF DownloadLoading ...

Performing accurate depth-imaging is an essential part of deep-water Gulf of Mexico exploration and development. Over the years, depth-imaging technology has provided reliable seismic images below complicated salt bodies, and has been implemented in workflows for both prospect generation as well as reservoir development. These workflows include time domain preprocessing using various multiple elimination techniques, anisotropic model building, and depth-imaging using anisotropic reverse time migration (RTM). However, the accuracy of the depth-migrated volumes is basically unknown because they are tested only in the locations where a well is drilled. In order to learn about the accuracy of anisotropic deep water Gulf of Mexico model building, and depth-imaging tools which are used for processing and imaging of field acquired data, we created a 3D vertical transverse isotropic (VTI) anisotropic earth model and a 3D seismic data set representing subsalt Gulf of Mexico geology. The model and data set are referred to as the Tempest data set, the original being created several years ago. The recent model and data set were created incorporating upgraded technology to reflect recent developments in data acquisition, model building and depth-imaging. Our paper presents the new Tempest anisotropic model, data set, and RTM prestack depth-migration (PSDM) results. The Tempest RTM PSDM is being used to learn about the differences between the exact geological model and the RTM PSDM image, helping in the interpretation of real RTM prestack depth-migrated data.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2009Multiples attenuation using WAZ data in VTI anisotropic media.Authors: Fatmir HoxhaDavid KesslerMike FrismanisJeff CoddFatmir HoxhaSeismicCity Inc.Search for more papers by this author, David KesslerSeismicCity Inc.Search for more papers by this author, Mike FrismanisSeismicCity Inc.Search for more papers by this author, and Jeff CoddSeismicCity Inc.Search for more papers by this authorhttps://doi.org/10.1190/1.3255063 SectionsSupplemental MaterialAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InReddit Abstract The work presented here illustrates the advantages of multiple attenuation when migrating wide‐azimuth (WAZ) data rather than narrow‐azimuth (NAZ) data. The multiple attenuation is demonstrated through a 3D anisotropic wave simulation and anisotropic Reverse time migration (RTM) of a salt related model case typical of the Gulf of Mexico (GOM) geology. The process includes construction of an anisotropic model followed by VTI wave equation simulation done with free‐surface boundary condition for recording of surface related multiples. One of the advantages of using a WAZ dataset for multiple attenuation is the fact that in this case the multiples are better spatially sampled than in the case of NAZ dataset. Of particular interest is not only in the influence of the input data (i.e. the specific type of WAZ dataset) but also the influence of the techniques used for the depth imaging. We investigate how the process of the multiple attenuation works when the geological model is anisotropic (Vertically Transversely Isotropy) rather than isotropic, and how prestack RTM handles the free‐surface generated multiples. Our conclusion is that depth migration of a WAZ dataset strongly attenuates multiples, and at the same time the use of prestack RTM can help in attenuation of multiples even when a NAZ dataset is used.Permalink: https://doi.org/10.1190/1.3255063FiguresReferencesRelatedDetails 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 Online: 14 Oct 2009 CITATION INFORMATION Fatmir Hoxha, David Kessler, Mike Frismanis, and Jeff Codd, (2009), "Multiples attenuation using WAZ data in VTI anisotropic media.," SEG Technical Program Expanded Abstracts : 1182-1186. https://doi.org/10.1190/1.3255063 Plain-Language Summary PDF DownloadLoading ...

Performing depth imaging is an essential part of deepwater Gulf of Mexico (GOM) exploration. Over the years, depth-imaging technology has provided the most reliable seismic images below salt and has been implemented in the workflows of the prospect generation process. But how accurate are these images? Since model building for depth imaging is partially an interpretative process, and depth imaging involves resolving seismic propagation through complicated geologic features, it is easy for the resulting prestack depth-migrated images to include imaging and positioning errors.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2008A realistic deep water Gulf of Mexico 3D simulation and imaging — The Tempest simulation, datasets and imagingAuthors: David KesslerJeff CoddFatmir HoxhaClaude PignolAlex BridgeRichard BrietzkeAdam SeitchikDana JurickDavid KesslerSeismicCity CorporationSearch for more papers by this author, Jeff CoddSeismicCity CorporationSearch for more papers by this author, Fatmir HoxhaSeismicCity CorporationSearch for more papers by this author, Claude PignolSeismicCity CorporationSearch for more papers by this author, Alex BridgeDevon Energy CorporationSearch for more papers by this author, Richard BrietzkeDevon Energy CorporationSearch for more papers by this author, Adam SeitchikDevon Energy CorporationSearch for more papers by this author, and Dana JurickDevon Energy CorporationSearch for more papers by this authorhttps://doi.org/10.1190/1.3054827 SectionsSupplemental MaterialAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract The Tempest 3D model and dataset were generated to test industry's ability to correctly image deep water Gulf of Mexico subsalt structures. The project included four steps: (a) design of a 3‐dimensional model based on real Gulf of Mexico geology; (b) acquisition design that included narrow azimuth, mid (range) azimuth and wide azimuth geometries; (c) numerical simulation using two‐ way wave equation algorithm and construction of three synthetic datasets; (d) application of various prestack depth migration algorithms for testing of subsalt imaging quality. The project parameters acquisition design and prestack depth migration algorithm parameters were all selected based on a single guideline: to be done as close as possible to field data acquisition and imaging. By following this guideline we obtained a dataset which realistically represents our ability to resolve subsalt imaging challenges. In this paper we present the project steps and demonstrate its main results.Permalink: https://doi.org/10.1190/1.3054827FiguresReferencesRelatedDetailsCited ByInvestigation of deep-water Gulf of Mexico subsalt imaging using anisotropic model, data set and RTM — TempestGEOPHYSICS, Vol. 76, No. 5 SEG Technical Program Expanded Abstracts 2008ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2008 Pages: 3713 publication data© 2008 Copyright © 2008 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished: 15 Dec 2008 CITATION INFORMATION David Kessler, Jeff Codd, Fatmir Hoxha, Claude Pignol, Alex Bridge, Richard Brietzke, Adam Seitchik, and Dana Jurick, (2008), "A realistic deep water Gulf of Mexico 3D simulation and imaging — The Tempest simulation, datasets and imaging," SEG Technical Program Expanded Abstracts : 378-382. https://doi.org/10.1190/1.3054827 Plain-Language Summary PDF DownloadLoading ...

The operational condition that dominates the survey planning and implementation is the presence of major shipping transit fairway to and from the Suez Canal. This shipping thoroughfare covers about 70% of the survey area. Operational considerations necessitate a shooting orientation that closely parallels the shipping lanes, which approximates the strike direction of the subsurface target. Shooting in the dip direction, across the shipping lanes, was not considered to be operationally feasible for a 3D spread or operation. A 3D seismic acquisition program took place in the northern Gulf of Suez, Egypt during early 2003 (figure 1). The marine towed streamer survey was preceded by an acquisition feasibility, design and modeling study that used a variety of techniques. The primary goal of the 3D survey design work was to specify and assess a set of key acquisition parameters that could be implemented in the field which, critically, had to support the successful implementation of modern demultiple, noise attenuation and 3D image processing techniques and technology. It was important to look for a solution that integrated operational realities and specific processing requirements. Previous 2D seismic acquisition programs in the area have utilized a limited offset streamer, presumably to accommodate dip and strike shooting through the shipping lanes. The 2D results typically suffer from marginal to very poor demultiple results and very poor imaging of the target structures. It was estimated that poor results were probably due to a combination of high residual noise levels related to limited demultiple technology and 2D imaging limitations. Exploration drilling results, based at least partially on the 2D datasets, have been disappointing to date. As a primary design tool on this project, we used 2D and 3D wave equation simulation. The aim of the wave equation simulation was to generate realistic synthetic seismograms that could be used to assess the effect of different field design parameters on exploration objectives. The goal was to design an economic and operationally feasible 3D survey that met the exploration objectives of our staff. This presentation will demonstrate how the wavefield simulation work was utilized and found to be useful for 3D seismic survey planning. Wave equation simulation was used in preparation of the acquisition program specifications. The technique was utilized to produce synthetic seismogram shot records that were in turn examined, interpreted and processed to assess the impact of various parameter combinations on meeting technical, operational and economic requirements set by the exploration staff. Introduction

Summary Despite improvements in 3-D imaging capabilities through the use of Pre-stack Depth Migration (PreSDM), interpretation of the resultant images in the areas of complex salt bodies is confused by additional events that are not primary PP reflections. This paper analyzes the results of seismic imaging underneath steeply dipping salt flanks using real and synthetic datasets. Based on real data problems, imaging of acoustic and elastic synthetic data sets show that some of the sub-salt sedimentary section may include converted waves. A practical way to correctly image these sub-salt converted waves is introduced.