Changes

  | part    = Critical elements of the petroleum system

  | part    = Critical elements of the petroleum system

  | chapter = Sedimentary basin analysis

  | chapter = Sedimentary basin analysis

  | frompg  = 4-1

  | frompg  = 4-103

  | topg    = 4-123

  | topg    = 4-105

  | author  = John M. Armentrout

  | author  = John M. Armentrout

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm

==Impact of growth-fault movement==

==Impact of growth-fault movement==

The multiple phases of petroleum charging the East Breaks 160-161 reservoirs and their accumulation within the anticlinal trap is interpreted to be controlled by the timing of [[Growth fault|growth-fault]] movement. Fault movement and fault-associated fracturing in the adjacent rocks could enhance the [[migration]] conduit. [[Migration]] up the fault would have provided petroleum charge into the intersected reservoir sandstones.

The multiple phases of petroleum charging the East Breaks 160-161 reservoirs and their [[accumulation]] within the anticlinal trap is interpreted to be controlled by the timing of [[Growth fault|growth-fault]] movement. Fault movement and fault-associated fracturing in the adjacent rocks could enhance the [[migration]] conduit. [[Migration]] up the fault would have provided [[Calculating charge volume|petroleum charge]] into the intersected reservoir sandstones.

==Fault movement and trap formation==

==Fault movement and trap formation==

[[File:Sedimentary-basin-analysis fig4-31.png|thumbnail|300px|{{figure number|1}}East Breaks, nine cycles between 1.2 Ma and the present. From Armentrout (1996); courtesy The Geological Society, London.]]

[[File:Sedimentary-basin-analysis fig4-31.png|thumbnail|300px|{{figure number|1}}East Breaks, nine cycles between 1.2 Ma and the present. From Armentrout;<ref name=Armentrout1996>Armentrout, J. M., 1996, High-resolution sequence biostratigraphy: examples from the Gulf of Mexico Plio–Pleistocene, in J. Howell and J. Aiken, eds., High Resolution Sequence Stratigraphy: Innovations and Applications: The Geological Society of London Special Publication 104, p. 65–86.</ref> courtesy The Geological Society, London.]]

Rollover into the [[Growth fault|growth-faul]]t-initiated trap formation occurred between about 1.2 Ma and the present. Fault movement occurred during each lowstand of sea level when differential loading from shelf-edge deltaic sedimentation and consequent salt withdrawal destabilized the upper slope system.<ref name=ch04r8>Armentrout, J., M., 1993, Relative seal-level variations and fault-salt response: offshore Texas examples: Proceedings, Gulf Coast Section SEPM 14th Annual Research Conference, p. 1–7.</ref> Given the sea-level fluctuation cycles documented within the East Breaks 160-161 minibasin<ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref><ref name=ch04r8 /> at least five and potentially nine lowstand events may have caused episodic movement of the north-bounding growth fault of the East Breaks 160-161 field ([[:File:Sedimentary-basin-analysis fig4-31.png|Figure 1]], nine cycles between 1.2 Ma and the present).

Rollover into the [[Growth fault|growth-faul]]t-initiated trap formation occurred between about 1.2 Ma and the present. Fault movement occurred during each lowstand of sea level when differential loading from shelf-edge deltaic sedimentation and consequent salt withdrawal destabilized the upper slope system.<ref name=ch04r8>Armentrout, J., M., 1993, Relative seal-level variations and fault-salt response: offshore Texas examples: Proceedings, Gulf Coast Section SEPM 14th Annual Research Conference, p. 1–7.</ref> Given the sea-level fluctuation cycles documented within the East Breaks 160-161 [[minibasin]]<ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref><ref name=ch04r8 /> at least five and potentially nine lowstand events may have caused episodic movement of the north-bounding growth fault of the East Breaks 160-161 field ([[:File:Sedimentary-basin-analysis fig4-31.png|Figure 1]], nine cycles between 1.2 Ma and the present).

==Sandbody geometries==

==Sandbody geometries==

<gallery mode=packed heights=300px widths=300px>

<gallery mode=packed heights=300px widths=300px>

file:sedimentary-basin-analysis_fig4-40.png|{{figure number|2}}East Breaks 160-161 mini basin.

file:sedimentary-basin-analysis_fig4-40.png|{{figure number|2}}East Breaks 160-161 mini basin.

file:sedimentary-basin-analysis_fig4-49.png|{{figure number|3}}Elongate and lobate north-to-south geometries. From Armentrout et al. (1991); courtesy Springer-Verlag.

file:sedimentary-basin-analysis_fig4-49.png|{{figure number|3}}Elongate and lobate north-to-south geometries. From Armentrout et al.;<ref name=Armentroutetal1991>Armentrout, J. M., S. J. Malacek, P. Braithwaite, and C. R. Beeman, 1991, Seismic facies of slope basin turbidite reservoirs, East Breaks 160-161 field: Pliocene–Pleistocene, northwestern Gulf of Mexico, in P. Weimer and M. J. Link, eds., Seismic Facies and Sedimentary Processes of Submarine Fans and Turbidite Systems: New York, Springer-Verlag, p. 223–239.</ref> courtesy Springer-Verlag.

file:sedimentary-basin-analysis_fig4-57.png|{{figure number|4}}seismic reflection amplitude pattern that shows north-to-south flank structural downdip termination.

file:sedimentary-basin-analysis_fig4-57.png|{{figure number|4}}seismic reflection amplitude pattern that shows north-to-south flank structural downdip termination.

</gallery>

</gallery>

The gravity-flow sandstone reservoirs within the field were transported from the north, southward into the East Breaks 160-161 mini basin ([[:file:sedimentary-basin-analysis_fig4-40.png|Figure 2]]), where the mapped pattern of the ''Glob alt'' sandstones show elongate and lobate north-to-south geometries ([[:file:sedimentary-basin-analysis_fig4-49.png|Figure 3]]). These north-to-south depositional geometries are draped over the east–west down-to-the-north rollover anticline, resulting in a seismic reflection amplitude pattern that shows north-to-south flank structural downdip termination ([[:file:sedimentary-basin-analysis_fig4-57.png|Figure 4C]]). East-to-west reflection amplitude termination is stratigraphically controlled by sand distribution. This petroleum-associated reflection amplitude pattern is in contrast to that for sheet sands that would drape over the entire structure and show four-way downdip structural termination of seismic reflection ([[:file:sedimentary-basin-analysis_fig4-57.png|Figure 4D]]).

The [[gravity]]-flow sandstone reservoirs within the field were transported from the north, southward into the East Breaks 160-161 mini basin ([[:file:sedimentary-basin-analysis_fig4-40.png|Figure 2]]), where the mapped pattern of the ''Glob alt'' sandstones show elongate and lobate north-to-south geometries ([[:file:sedimentary-basin-analysis_fig4-49.png|Figure 3]]). These north-to-south depositional geometries are draped over the east–west down-to-the-north rollover anticline, resulting in a seismic reflection amplitude pattern that shows north-to-south flank structural downdip termination ([[:file:sedimentary-basin-analysis_fig4-57.png|Figure 4C]]). East-to-west reflection amplitude termination is stratigraphically controlled by sand distribution. This petroleum-associated reflection amplitude pattern is in contrast to that for sheet sands that would drape over the entire structure and show four-way downdip structural termination of seismic reflection ([[:file:sedimentary-basin-analysis_fig4-57.png|Figure 4D]]).

==Tying seismic to well data==

==Tying seismic to well data==

[[:File:Sedimentary-basin-analysis fig4-57.png|Figure 4]] is a seismic reflection profile across the East Breaks 160-161 field, showing the 160 No. 1 well SP log and [[synthetic seismogram]] and two schematic diagrams for interpreting possible seismic reflection amplitude anomaly maps, which could indicate hydrocarbon-charged sands. Bioevent horizons correlate with the top seal above each reservoir interval. Only the lower ''Trim A'' and ''Glob alt'' reservoir sandstones are well developed in this well. The depositional model for a delta-front sheet sand extending over the entire postdepositional anticline is likely to have four-way downdip termination of petroleum-associated seismic reflection amplitude anomalies ([[:File:Sedimentary-basin-analysis fig4-57.png|Figure 4C]]). The depositional model for a depositional dip-oriented gravity-flow sandstone draped over the postdepositional anticline is likely to have two-way structural termination of a petroleum-associated seismic reflection amplitude anomaly, with stratigraphic termination of reflectors along both depositional-strike directions ([[:File:Sedimentary-basin-analysis fig4-57.png|Figure 4D]]). The mapped amplitude pattern in both the ''Trim A'' and ''Glob alt'' intervals agrees with a channel-fed gravity-flow depositional system.

[[:File:Sedimentary-basin-analysis fig4-57.png|Figure 4]] is a seismic reflection profile across the East Breaks 160-161 field, showing the 160 No. 1 well SP log and [[synthetic seismogram]] and two schematic diagrams for interpreting possible seismic reflection amplitude anomaly maps, which could indicate hydrocarbon-charged sands. Bioevent horizons correlate with the top seal above each reservoir interval. Only the lower ''Trim A'' and ''Glob alt'' reservoir sandstones are well developed in this well. The depositional model for a delta-front sheet sand extending over the entire postdepositional anticline is likely to have four-way downdip termination of petroleum-associated seismic reflection amplitude anomalies ([[:File:Sedimentary-basin-analysis fig4-57.png|Figure 4C]]). The depositional model for a depositional [[dip]]-oriented gravity-flow sandstone draped over the postdepositional anticline is likely to have two-way structural termination of a petroleum-associated seismic reflection amplitude anomaly, with stratigraphic termination of reflectors along both depositional-strike directions ([[:File:Sedimentary-basin-analysis fig4-57.png|Figure 4D]]). The mapped amplitude pattern in both the ''Trim A'' and ''Glob alt'' intervals agrees with a channel-fed gravity-flow depositional system.

==Recharging of reservoirs==

==Recharging of reservoirs==

Preserving these petroleum resources has been discussed in reference to biodegradation, which has produced much of the gas in the reservoirs—especially at the ''Trim A'' horizon. Burial of the reservoirs to depths with temperatures in excess of [[temperature::140&deg;F]] ([[temperature::60&deg;C]]) prevents further microbial degradation of the oil. Late episodes of fault movement facilitates recharging the reservoirs with higher maturity oil, migrating upward from the deeply buried active [[source rock]] that is not yet specifically identified (see Anderson<ref name=ch04r1>Anderson, R., N., 1993, [http://www.ogj.com/articles/print/volume-91/issue-17/in-this-issue/exploration/recovering-dynamic-gulf-of-mexico-reserves-and-the-us-energy-future.html Recovering dynamic Gulf of Mexico reserves and the U., S. energy future]: Oil & Gas Journal, 26 April 1993, p. 85–88, 90–92.</ref><ref name=ch04r2>Anderson, R., N., Flemings, P., Losh, S., Austin, J., Woodhams, R., 1994, [http://www.ogj.com/articles/print/volume-92/issue-23/in-this-issue/exploration/gulf-of-mexico-growth-fault-drilled-seen-as-oil-gas-migration-pathway.html Gulf of Mexico growth fault drilled, seen as oil, gas migration pathway]: Oil & Gas Journal, 6 June 1994, p. 97–104.</ref>).

Preserving these petroleum resources has been discussed in reference to [[biodegradation]], which has produced much of the gas in the reservoirs—especially at the ''Trim A'' horizon. Burial of the reservoirs to depths with temperatures in excess of [[temperature::140&deg;F]] ([[temperature::60&deg;C]]) prevents further microbial degradation of the oil. Late episodes of fault movement facilitates recharging the reservoirs with higher maturity oil, migrating upward from the deeply buried active [[source rock]] that is not yet specifically identified (see Anderson<ref name=ch04r1>Anderson, R., N., 1993, [http://www.ogj.com/articles/print/volume-91/issue-17/in-this-issue/exploration/recovering-dynamic-gulf-of-mexico-reserves-and-the-us-energy-future.html Recovering dynamic Gulf of Mexico reserves and the U., S. energy future]: Oil & Gas Journal, 26 April 1993, p. 85–88, 90–92.</ref><ref name=ch04r2>Anderson, R., N., Flemings, P., Losh, S., Austin, J., Woodhams, R., 1994, [http://www.ogj.com/articles/print/volume-92/issue-23/in-this-issue/exploration/gulf-of-mexico-growth-fault-drilled-seen-as-oil-gas-migration-pathway.html Gulf of Mexico growth fault drilled, seen as oil, gas migration pathway]: Oil & Gas Journal, 6 June 1994, p. 97–104.</ref>).

==See also==

==See also==

[[Category:Sedimentary basin analysis]]

[[Category:Sedimentary basin analysis]]

[[Category:East Breaks]]

[[Category:East Breaks]]