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Seismic sequence analysis (view source)
Revision as of 18:50, 22 January 2014
, 18:50, 22 January 2014Initial import
{{publication
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Exploring for stratigraphic traps
| frompg = 21-1
| topg = 21-68
| author = John C. Dolson, Mike S. Bahorich, Rick C. Tobin, Edward A. Beaumont, Louis J. Terlikoski, Michael L. Hendricks
| link = http://archives.datapages.com/data/specpubs/beaumont/ch21/ch21.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
==Objective==
The objective of seismic sequence analysis is to identify depositional sequences and systems tracts on seismic sections by interpreting the location of their boundaries. Boundaries are manifested as discontinuities in seismic sections and are located mainly by finding reflection terminations.<ref name=ch21r44>Vail, P., R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A., W., ed., Atlas of Seismic Stratigraphy: AAPG Studies in Geology No. 27, p. 2.</ref>
==Procedure==
Follow the steps listed in the table below to perform a sequence analysis of a seismic section (adapted from <ref name=ch21r44 />).
{| class = "wikitable"
|-
! Step
! Action
|-
| 1
| Look for places where two reflectors converge. Where reflectors converge, there will be terminations.
|-
| 2
| Mark the reflection terminations with arrows.
|-
| 3
| Draw in the discontinuity surface between the onlapping and downlapping reflections above, and the truncating and toplapping reflectors above. If the discontinuity surface becomes conformable, trace its position across the section by reflection correlation.
|-
| 4
| Continue the process described in steps 1, 2, and 3 for all the seismic lines in the grid.
|-
| 5
| Close all seismic grid loops by checking the loop ties for each discontinuity or its correlative equivalent.
|-
| 6
| Categorize each discontinuity.
* <table-wrap id="ch21utbl8a" position="float"> <table frame="hsides"> <colgroup> <col align="left"></col> <col align="left"></col> </colgroup> <thead> <tr> <th align="center"> If </th> <th align="center"> Then... </th> </tr> </thead> <tbody> <tr> <td align="left"> It is characterized by regional onlap above and truncation below It is probably a sequence boundary </td></tr> <tr> It is characterized by regional downlap It is most likely a downlap surface </tr> </tbody> </table> </table-wrap>
|-
| <th align="center"> If</th>
| <th align="center"> Then...</th>
|-
| It is characterized by regional onlap above and truncation below
| It is probably a sequence boundary
|-
| It is characterized by regional downlap
| It is most likely a downlap surface
|}
==Marking a seismic section, marking==
The table below shows suggested colors for marking seismic sections during sequence analysis (after <ref name=ch21r44 />).
{| class = "wikitable"
|-
! Feature
! Color
|-
| Reflection terminations and reflection patterns
| Red
|-
| Downlap surfaces
| Green
|-
| Transgressive surfaces
| Blue
|-
| Sequence boundaries
| Miscellaneous
|}
==Reflection terminations==
The table below groups termination patterns by position with respect to a discontinuity.
{| class = "wikitable"
|-
! Reflection termination point
! Pattern
! Associated discontinuity
|-
| Above a discontinuity
| Onlap
| Sequence boundary (unconformity)
|-
| Downlap
| Downlap surface (condensed section)
|-
| Below a discontinuity
| Truncation
| Sequence boundary
|-
| Toplap
| Sequence boundary
|-
| Apparent truncation
| Downlap surface
|}
==Locating reflection terminations==
Locating reflection termination is a matter of finding the patterns described in the table above. The figure below shows these patterns and the associated discontinuity surfaces. HST is highstand systems tract, LST is lowstand systems tract, and TST is transgressive systems tract.
[[file:exploring-for-stratigraphic-traps_fig21-18.png|thumb|{{figure number|21-18}}.]]
==See also==
* [[Geometrical analysis]]
* [[Procedure for geometrical analysis]]
* [[Other correlation features]]
* [[Well log sequence analysis]]
* [[Combining well log with seismic sequence analysis]]
==References==
{{reflist}}
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch21/ch21.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Exploring for stratigraphic traps]]
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Exploring for stratigraphic traps
| frompg = 21-1
| topg = 21-68
| author = John C. Dolson, Mike S. Bahorich, Rick C. Tobin, Edward A. Beaumont, Louis J. Terlikoski, Michael L. Hendricks
| link = http://archives.datapages.com/data/specpubs/beaumont/ch21/ch21.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
==Objective==
The objective of seismic sequence analysis is to identify depositional sequences and systems tracts on seismic sections by interpreting the location of their boundaries. Boundaries are manifested as discontinuities in seismic sections and are located mainly by finding reflection terminations.<ref name=ch21r44>Vail, P., R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A., W., ed., Atlas of Seismic Stratigraphy: AAPG Studies in Geology No. 27, p. 2.</ref>
==Procedure==
Follow the steps listed in the table below to perform a sequence analysis of a seismic section (adapted from <ref name=ch21r44 />).
{| class = "wikitable"
|-
! Step
! Action
|-
| 1
| Look for places where two reflectors converge. Where reflectors converge, there will be terminations.
|-
| 2
| Mark the reflection terminations with arrows.
|-
| 3
| Draw in the discontinuity surface between the onlapping and downlapping reflections above, and the truncating and toplapping reflectors above. If the discontinuity surface becomes conformable, trace its position across the section by reflection correlation.
|-
| 4
| Continue the process described in steps 1, 2, and 3 for all the seismic lines in the grid.
|-
| 5
| Close all seismic grid loops by checking the loop ties for each discontinuity or its correlative equivalent.
|-
| 6
| Categorize each discontinuity.
* <table-wrap id="ch21utbl8a" position="float"> <table frame="hsides"> <colgroup> <col align="left"></col> <col align="left"></col> </colgroup> <thead> <tr> <th align="center"> If </th> <th align="center"> Then... </th> </tr> </thead> <tbody> <tr> <td align="left"> It is characterized by regional onlap above and truncation below It is probably a sequence boundary </td></tr> <tr> It is characterized by regional downlap It is most likely a downlap surface </tr> </tbody> </table> </table-wrap>
|-
| <th align="center"> If</th>
| <th align="center"> Then...</th>
|-
| It is characterized by regional onlap above and truncation below
| It is probably a sequence boundary
|-
| It is characterized by regional downlap
| It is most likely a downlap surface
|}
==Marking a seismic section, marking==
The table below shows suggested colors for marking seismic sections during sequence analysis (after <ref name=ch21r44 />).
{| class = "wikitable"
|-
! Feature
! Color
|-
| Reflection terminations and reflection patterns
| Red
|-
| Downlap surfaces
| Green
|-
| Transgressive surfaces
| Blue
|-
| Sequence boundaries
| Miscellaneous
|}
==Reflection terminations==
The table below groups termination patterns by position with respect to a discontinuity.
{| class = "wikitable"
|-
! Reflection termination point
! Pattern
! Associated discontinuity
|-
| Above a discontinuity
| Onlap
| Sequence boundary (unconformity)
|-
| Downlap
| Downlap surface (condensed section)
|-
| Below a discontinuity
| Truncation
| Sequence boundary
|-
| Toplap
| Sequence boundary
|-
| Apparent truncation
| Downlap surface
|}
==Locating reflection terminations==
Locating reflection termination is a matter of finding the patterns described in the table above. The figure below shows these patterns and the associated discontinuity surfaces. HST is highstand systems tract, LST is lowstand systems tract, and TST is transgressive systems tract.
[[file:exploring-for-stratigraphic-traps_fig21-18.png|thumb|{{figure number|21-18}}.]]
==See also==
* [[Geometrical analysis]]
* [[Procedure for geometrical analysis]]
* [[Other correlation features]]
* [[Well log sequence analysis]]
* [[Combining well log with seismic sequence analysis]]
==References==
{{reflist}}
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch21/ch21.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Exploring for stratigraphic traps]]