Changes

==Transgressive and highstand systems tracts==

==Transgressive and highstand systems tracts==

Accommodation rates are high during transgressive–early highstand episodes of sea level, forming thick reservoirs of excellent quality. Shales in the upper transgressive systems tract and lower highstand systems tract are generally high-quality seals. Updip and bottom seals can be a problem for stratigraphic traps. Unconformity truncations, onlapping sands, and mounded shoreline sands form stratigraphic traps. Siliciclastics of the late highstand generally are poor reservoirs. Excellent source rocks are associated with the starved portion of the transgressive and early highstand systems tracts. Coals and terrestrial source rocks also are associated with the transgressive and early highstand systems tracts.

Accommodation rates are high during transgressive–early highstand episodes of sea level, forming thick reservoirs of excellent quality. Shales in the upper transgressive systems tract and lower highstand systems tract are generally high-quality seals. Updip and bottom seals can be a problem for stratigraphic traps. Unconformity truncations, onlapping sands, and mounded shoreline sands form stratigraphic traps. Siliciclastics of the late highstand generally are poor reservoirs. Excellent source rocks are associated with the starved portion of the transgressive and early highstand systems tracts. Coals and terrestrial source rocks also are associated with the transgressive and early highstand systems tracts.

==Lowstand systems tracts==

==Lowstand systems tracts==

==Lowstand systems tract traps==

==Lowstand systems tract traps==

The diagrammatic cross section that follows and the corresponding table describe six potential trap types associated with the lowstand systems tract.

The diagrammatic cross section ([[:file:exploring-for-stratigraphic-traps_fig21-37.png|Figure 1]] and the corresponding table describe six potential trap types associated with the lowstand systems tract.

 

[[file:exploring-for-stratigraphic-traps_fig21-37.png|thumb|{{figure number|21-37}}.]]

{| class = "wikitable"

{| class = "wikitable"

| Good reservoirs. In sandy systems, basin floor fans are shingled and pinch out between the shale toes of lowstand prograding wedge.

| Good reservoirs. In sandy systems, basin floor fans are shingled and pinch out between the shale toes of lowstand prograding wedge.

|}

|}

==Plays in different margin types==

==Plays in different margin types==

Different margin types in basins have different play types determined by the geometry and history of the margin. The figure below shows play types for shelf-edge and ramp margins.

Different margin types in basins have different play types determined by the geometry and history of the margin. [[:file:exploring-for-stratigraphic-traps_fig21-38.png|Figure 2]] shows play types for shelf-edge and ramp margins.

[[file:exploring-for-stratigraphic-traps_fig21-38.png|thumb|{{figure number|21-38}}.]]

[[file:exploring-for-stratigraphic-traps_fig21-39.png|left|thumb|{{figure number|3}}See text for explanation.]]

==Example: integrating petrophysics and geology==

==Example: integrating petrophysics and geology==

Unpublished data (courtesy Amoco Production Company) derived from cores and [[seismic data]] were used to build an integrated lithofacies map. The figure below is a cross section representing the reservoir properties from representative [[capillary pressure]] data. The facies belts shown in the map above the cross section were deposited during maximum highstand of the Ismay (Pennsylvanian) carbonates. The fades are superimposed on an isopach map of the highstand systems tract. Test and show data overlain on the map show that significant reservoirs are restricted generally in the ''Ivanovia'' algal mound buildups, which flank a highstand basin shown in gray.

Unpublished data (courtesy Amoco Production Company) derived from cores and [[seismic data]] were used to build an integrated lithofacies map. [[:file:exploring-for-stratigraphic-traps_fig21-39.png|Figure 3]] is a cross section representing the reservoir properties from representative [[capillary pressure]] data. The facies belts shown in the map above the cross section were deposited during maximum highstand of the Ismay (Pennsylvanian) carbonates. The fades are superimposed on an isopach map of the highstand systems tract. Test and show data overlain on the map show that significant reservoirs are restricted generally in the ''Ivanovia'' algal mound buildups, which flank a highstand basin shown in gray.

 

==See also==

==See also==