Changes

==Seal geometry==

==Seal geometry==

[[file:exploring-for-stratigraphic-traps_fig21-1.png|300px|thumb|{{figure number|1}}See text for explanation.]]

[[file:exploring-for-stratigraphic-traps_fig21-1.png|300px|thumb|{{figure number|1}}Comparison of typical structural and stratigraphic traps and shows why bottom seals are more important to stratigraphic traps in determining accumulation size.]]

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

Most [[Stratigraphic trap|stratigraphic]] and [[combination trap]]s require top, lateral, and bottom [[seal]]s to retain a hydrocarbon [[accumulation]]. [[:file:exploring-for-stratigraphic-traps_fig21-1.png|Figure 1]] compares typical [[Structural trap system|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|300px|{{figure number|2}}See text for explanation.]]

[[file:exploring-for-stratigraphic-traps_fig21-2.png|thumb|300px|{{figure number|2}}How dip rate affects stratigraphic trap size.]]

==Seal quality and dip rate==

==Seal quality and dip rate==

==Example==

==Example==

[[file:exploring-for-stratigraphic-traps_fig21-3.png|300px|thumb|{{figure number|3}}See text for explanation.]]

[[file:exploring-for-stratigraphic-traps_fig21-3.png|300px|thumb|{{figure number|3}}Map and cross section of Raven Creek field.]]

Raven Creek field (with 40 million BOE) illustrates the importance of a bottom seal. It is a paleotopographic trap in the [[Powder River basin]] of Wyoming. An [[unconformity]] overlying the “A” sandstone of the [[Permian]] [[Minnelusa Formation]] determines the primary trap geometry. This unconformity has paleotopographic relief, and the [[Opeche Shale]] [[red beds]] are [[sabkha]] deposits that infill an erosional valley forming the top and lateral seals to the “A” sandstone reservoir. The [[dolostone]] bed separating reservoir sandstones “A” and “B” provides the bottom seal.

Raven Creek field (with 40 million BOE) illustrates the importance of a bottom seal. It is a paleotopographic trap in the [[Powder River basin]] of Wyoming. An [[unconformity]] overlying the “A” sandstone of the [[Permian]] [[Minnelusa Formation]] determines the primary trap geometry. This unconformity has paleotopographic relief, and the [[Opeche Shale]] [[red beds]] are [[sabkha]] deposits that infill an erosional valley forming the top and lateral seals to the “A” sandstone reservoir. The [[dolostone]] bed separating reservoir sandstones “A” and “B” provides the bottom seal.