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Subsalt pressure prediction in the Miocene Mad Dog field, Gulf of Mexico.

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Title: Subsalt pressure prediction in the Miocene Mad Dog field, Gulf of Mexico.
Authors: Merrell, Michael P.1 michael.p.merrell@conocophillips.com, Flemings, Peter B.2 pflemings@jsg.utexas.edu, Bowers, Glenn L.3 glbowers-amt@comcast.net
Source: AAPG Bulletin. Feb2014, Vol. 98 Issue 2, p315-340. 26p.
Subjects: Sandstone, Hydrostatics, Mudstone, Boreholes, Porosity
Abstract: Sandstone pressures follow the hydrostatic gradient in Miocene strata of the Mad Dog field, deep-water Gulf of Mexico, whereas pore pressures in the adjacent mudstones track a trend from well to well that can be approximated by the total vertical stress gradient. The sandstone pressures within these strata are everywhere less than the bounding mudstone pore pressures, and the difference between them is proportional to the total vertical stress. The mudstone pressure is predicted from its porosity with an exponential porosity-versus-vertical effective stress relationship, where porosity is interpreted from wireline velocity. Sonic velocities in mudstones bounding the regional sandstones fall within a narrow range throughout the field from which we interpret their vertical effective stresses can be approximated as constant. We show how to predict sandstone and mudstone pore pressure in any offset well at Mad Dog given knowledge of the local total vertical stress. At Mad Dog, the approach is complicated by the extraordinary lateral changes in total vertical stress that are caused by changing bathymetry and the presence or absence of salt. A similar approach can be used in other subsalt fields. We suggest that pore pressures within mudstones can be systematically different from those of the nearby sandstones, and that this difference can be predicted. Well programs must ensure that the borehole pressure is not too low, which results in borehole closure in the mudstone intervals, and not too high, which can result in lost circulation to the reservoir intervals. [ABSTRACT FROM AUTHOR]
Copyright of AAPG Bulletin is the property of American Association of Petroleum Geologists 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.)
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  Data: Subsalt pressure prediction in the Miocene Mad Dog field, Gulf of Mexico.
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  Data: <searchLink fieldCode="AR" term="%22Merrell%2C+Michael+P%2E%22">Merrell, Michael P.</searchLink><relatesTo>1</relatesTo><i> michael.p.merrell@conocophillips.com</i><br /><searchLink fieldCode="AR" term="%22Flemings%2C+Peter+B%2E%22">Flemings, Peter B.</searchLink><relatesTo>2</relatesTo><i> pflemings@jsg.utexas.edu</i><br /><searchLink fieldCode="AR" term="%22Bowers%2C+Glenn+L%2E%22">Bowers, Glenn L.</searchLink><relatesTo>3</relatesTo><i> glbowers-amt@comcast.net</i>
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  Data: <searchLink fieldCode="JN" term="%22AAPG+Bulletin%22">AAPG Bulletin</searchLink>. Feb2014, Vol. 98 Issue 2, p315-340. 26p.
– Name: Subject
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  Data: <searchLink fieldCode="DE" term="%22Sandstone%22">Sandstone</searchLink><br /><searchLink fieldCode="DE" term="%22Hydrostatics%22">Hydrostatics</searchLink><br /><searchLink fieldCode="DE" term="%22Mudstone%22">Mudstone</searchLink><br /><searchLink fieldCode="DE" term="%22Boreholes%22">Boreholes</searchLink><br /><searchLink fieldCode="DE" term="%22Porosity%22">Porosity</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Sandstone pressures follow the hydrostatic gradient in Miocene strata of the Mad Dog field, deep-water Gulf of Mexico, whereas pore pressures in the adjacent mudstones track a trend from well to well that can be approximated by the total vertical stress gradient. The sandstone pressures within these strata are everywhere less than the bounding mudstone pore pressures, and the difference between them is proportional to the total vertical stress. The mudstone pressure is predicted from its porosity with an exponential porosity-versus-vertical effective stress relationship, where porosity is interpreted from wireline velocity. Sonic velocities in mudstones bounding the regional sandstones fall within a narrow range throughout the field from which we interpret their vertical effective stresses can be approximated as constant. We show how to predict sandstone and mudstone pore pressure in any offset well at Mad Dog given knowledge of the local total vertical stress. At Mad Dog, the approach is complicated by the extraordinary lateral changes in total vertical stress that are caused by changing bathymetry and the presence or absence of salt. A similar approach can be used in other subsalt fields. We suggest that pore pressures within mudstones can be systematically different from those of the nearby sandstones, and that this difference can be predicted. Well programs must ensure that the borehole pressure is not too low, which results in borehole closure in the mudstone intervals, and not too high, which can result in lost circulation to the reservoir intervals. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of AAPG Bulletin is the property of American Association of Petroleum Geologists 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: 10.1306/06251312156
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 26
        StartPage: 315
    Subjects:
      – SubjectFull: Sandstone
        Type: general
      – SubjectFull: Hydrostatics
        Type: general
      – SubjectFull: Mudstone
        Type: general
      – SubjectFull: Boreholes
        Type: general
      – SubjectFull: Porosity
        Type: general
    Titles:
      – TitleFull: Subsalt pressure prediction in the Miocene Mad Dog field, Gulf of Mexico.
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            NameFull: Merrell, Michael P.
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            NameFull: Flemings, Peter B.
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            NameFull: Bowers, Glenn L.
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            – D: 01
              M: 02
              Text: Feb2014
              Type: published
              Y: 2014
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              Value: 98
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