Changes

==Seal geometry==

==Seal geometry==

Most stratigraphic and combination traps require top, lateral, and bottom seals to retain a hydrocarbon accumulation. The figure below compares typical structural and stratigraphic traps and shows why bottom seals are more important to stratigraphic traps in determining accumulation size.

[[file:exploring-for-stratigraphic-traps_fig21-1.png|left|thumb|{{figure number|21}}See text for explanation.]]

[[file:exploring-for-stratigraphic-traps_fig21-1.png|thumb|{{figure number|21-1}}See text for explanation.]]

Most stratigraphic and combination traps require top, lateral, and bottom seals to retain a hydrocarbon accumulation. [[:file:exploring-for-stratigraphic-traps_fig21-1.png|Figure 1]] compares typical structural and stratigraphic traps and shows why bottom seals are more important to stratigraphic traps in determining accumulation size.

 

[[file:exploring-for-stratigraphic-traps_fig21-2.png|thumb|{{figure number|2}}See text for explanation.]]

==Seal quality and dip rate==

==Seal quality and dip rate==

Large stratigraphic traps are most common in basins with gentle structural dip, where small hydrocarbon columns can be areally extensive. As structural dip steepens, the need for high-quality seals increases, raising the probability of trap failure (e.g., .<ref name=ch21r19>Gries, R., Dolson, J., C., Reynolds, R., G., H., 1993, Structural and stratigraphic evolution and hydrocarbon distribution, Rocky Mountain Foreland, in Macqueen, R., W., Leckie, D., A., eds., Foreland Basins and Fold Belts: AAPG Memoir 55, p. 395–425.</ref> That is why large stratigraphic traps are most common in basins with gentle structural dip, where small hydrocarbon columns can be areally extensive. The figure below illustrates in map view how dip rate affects stratigraphic trap size.

Large stratigraphic traps are most common in basins with gentle structural dip, where small hydrocarbon columns can be areally extensive. As structural dip steepens, the need for high-quality seals increases, raising the probability of trap failure (e.g., .<ref name=ch21r19>Gries, R., Dolson, J., C., Reynolds, R., G., H., 1993, Structural and stratigraphic evolution and hydrocarbon distribution, Rocky Mountain Foreland, in Macqueen, R., W., Leckie, D., A., eds., Foreland Basins and Fold Belts: AAPG Memoir 55, p. 395–425.</ref> That is why large stratigraphic traps are most common in basins with gentle structural dip, where small hydrocarbon columns can be areally extensive. [[:file:exploring-for-stratigraphic-traps_fig21-2.png|Figure 2]] illustrates in map view how dip rate affects stratigraphic trap size.

[[file:exploring-for-stratigraphic-traps_fig21-2.png|thumb|{{figure number|21-2}}See text for explanation.]]

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

==Example==

==Example==

A trap would not form if the valley fill were composed of porous sand or if the bottom-sealing dolostone were absent (from unpublished data by Ralph Thompson, 1986).

A trap would not form if the valley fill were composed of porous sand or if the bottom-sealing dolostone were absent (from unpublished data by Ralph Thompson, 1986).

[[:file:exploring-for-stratigraphic-traps_fig21-3.png|Figure 3]] shows a map and cross section of Raven Creek field.

 

[[file:exploring-for-stratigraphic-traps_fig21-3.png|thumb|{{figure number|21-3}}See text for explanation.]]

==[[Reservoir quality]] and column height==

==[[Reservoir quality]] and column height==