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Improving sub-salt imaging using 3D basin model derived velocities

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Title: Improving sub-salt imaging using 3D basin model derived velocities
Authors: Petmecky, R. Stephan1 petmecs@bp.com, Albertin, Martin L.2, Burke, Nick2
Source: Marine & Petroleum Geology. Apr2009, Vol. 26 Issue 4, p457-463. 7p.
Subjects: Salt deposits, Geological basins, Geological modeling, Three-dimensional imaging, Image quality analysis, Seismograms
Geographic Terms: Gulf of Mexico, Mexico
Abstract: Abstract: The quality of depth imaging is directly related to the accuracy of the underlying velocity model. In most sub-salt settings, lack of angular illumination severely degrades the resolution and accuracy of velocity information derived from the seismic data itself. A standard approach for building a starting velocity model uses more reliable velocity information outboard of salt which is subsequently extrapolated to populate the sub-salt regions. The shortcoming of this method lies in the assumption that the effective stress observed outboard of salt can be extrapolated beneath salt solely as a function of depth below mudline. Velocities derived from basin model effective stress data show excellent large-scale agreement to seismic velocities. 3D basin modeling represents the most rigorous approach for determining sub-salt effective stresses because it accounts for depositional history, sand distribution and connectivity, variable shale properties, timing of salt emplacement – all of which influence the magnitude and distribution of abnormal pore pressure. In the presented study a calibrated present day effective stress cube from a 3D basin model was used to calculate sub-salt velocities for an exploration well in the Central Gulf of Mexico. The comparison between basin modeling derived velocities and the original velocity field showed remarkable differences, particularly in that the former indicated a far more complex sub-salt velocity distribution than the latter. Utilizing basin model sediment velocities to re-migrate the seismic data set resulted in a more detailed image as well as changed source rock geometries. Where the original image showed a deep de-focus at the source rock level, the new geometry would focus hydrocarbons into the identified trap. Based on the results of the subsequently drilled exploration well, it has to be assumed that the re-migrated data, aided by basin modeling derived velocities, provide a more accurate image of the sub-salt geology. [Copyright &y& Elsevier]
Copyright of Marine & Petroleum Geology is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
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Header DbId: egs
DbLabel: Engineering Source
An: 37349646
AccessLevel: 6
PubType: Academic Journal
PubTypeId: academicJournal
PreciseRelevancyScore: 0
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  Data: Improving sub-salt imaging using 3D basin model derived velocities
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  Data: <searchLink fieldCode="AR" term="%22Petmecky%2C+R%2E+Stephan%22">Petmecky, R. Stephan</searchLink><relatesTo>1</relatesTo><i> petmecs@bp.com</i><br /><searchLink fieldCode="AR" term="%22Albertin%2C+Martin+L%2E%22">Albertin, Martin L.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Burke%2C+Nick%22">Burke, Nick</searchLink><relatesTo>2</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Marine+%26+Petroleum+Geology%22">Marine & Petroleum Geology</searchLink>. Apr2009, Vol. 26 Issue 4, p457-463. 7p.
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  Data: <searchLink fieldCode="DE" term="%22Salt+deposits%22">Salt deposits</searchLink><br /><searchLink fieldCode="DE" term="%22Geological+basins%22">Geological basins</searchLink><br /><searchLink fieldCode="DE" term="%22Geological+modeling%22">Geological modeling</searchLink><br /><searchLink fieldCode="DE" term="%22Three-dimensional+imaging%22">Three-dimensional imaging</searchLink><br /><searchLink fieldCode="DE" term="%22Image+quality+analysis%22">Image quality analysis</searchLink><br /><searchLink fieldCode="DE" term="%22Seismograms%22">Seismograms</searchLink>
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  Data: <searchLink fieldCode="DE" term="%22Gulf+of+Mexico%22">Gulf of Mexico</searchLink><br /><searchLink fieldCode="DE" term="%22Mexico%22">Mexico</searchLink>
– Name: Abstract
  Label: Abstract
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  Data: Abstract: The quality of depth imaging is directly related to the accuracy of the underlying velocity model. In most sub-salt settings, lack of angular illumination severely degrades the resolution and accuracy of velocity information derived from the seismic data itself. A standard approach for building a starting velocity model uses more reliable velocity information outboard of salt which is subsequently extrapolated to populate the sub-salt regions. The shortcoming of this method lies in the assumption that the effective stress observed outboard of salt can be extrapolated beneath salt solely as a function of depth below mudline. Velocities derived from basin model effective stress data show excellent large-scale agreement to seismic velocities. 3D basin modeling represents the most rigorous approach for determining sub-salt effective stresses because it accounts for depositional history, sand distribution and connectivity, variable shale properties, timing of salt emplacement – all of which influence the magnitude and distribution of abnormal pore pressure. In the presented study a calibrated present day effective stress cube from a 3D basin model was used to calculate sub-salt velocities for an exploration well in the Central Gulf of Mexico. The comparison between basin modeling derived velocities and the original velocity field showed remarkable differences, particularly in that the former indicated a far more complex sub-salt velocity distribution than the latter. Utilizing basin model sediment velocities to re-migrate the seismic data set resulted in a more detailed image as well as changed source rock geometries. Where the original image showed a deep de-focus at the source rock level, the new geometry would focus hydrocarbons into the identified trap. Based on the results of the subsequently drilled exploration well, it has to be assumed that the re-migrated data, aided by basin modeling derived velocities, provide a more accurate image of the sub-salt geology. [Copyright &y& Elsevier]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Marine & Petroleum Geology is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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    Identifiers:
      – Type: doi
        Value: 10.1016/j.marpetgeo.2009.01.011
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 7
        StartPage: 457
    Subjects:
      – SubjectFull: Salt deposits
        Type: general
      – SubjectFull: Geological basins
        Type: general
      – SubjectFull: Geological modeling
        Type: general
      – SubjectFull: Three-dimensional imaging
        Type: general
      – SubjectFull: Image quality analysis
        Type: general
      – SubjectFull: Seismograms
        Type: general
      – SubjectFull: Gulf of Mexico
        Type: general
      – SubjectFull: Mexico
        Type: general
    Titles:
      – TitleFull: Improving sub-salt imaging using 3D basin model derived velocities
        Type: main
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          Name:
            NameFull: Petmecky, R. Stephan
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            NameFull: Albertin, Martin L.
      – PersonEntity:
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            NameFull: Burke, Nick
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          Dates:
            – D: 01
              M: 04
              Text: Apr2009
              Type: published
              Y: 2009
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              Value: 02648172
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            – Type: volume
              Value: 26
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              Value: 4
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            – TitleFull: Marine & Petroleum Geology
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