Changes

==Geometry==

==Geometry==

[[File:M91FG67.JPG|thumb|300px|{{figure number|2}}Shingled geometries are common in certain depositional environments and can result in a number of isolated reservoir segments. However, this type of geometry is easy to overlook, and a layer-cake geometry is often erroneously imposed (from Sneider and Sneider).<ref name=Sneider2>Sneider, R. M., and J. S. Sneider, 2001, [http://archives.datapages.com/data/specpubs/memoir74/m74ch06/m74ch06.htm New oil in old places: The value of mature-field development], in M. W. Downey, J. C. Threet, and W. A. Morgan, eds., Petroleum provinces of the twenty-first century: [http://store.aapg.org/detail.aspx?id=77 AAPG Memoir 74], p. 63–84.</ref> Reprinted with permission from the AAPG.]]

[[File:M91FG67.JPG|thumb|300px|{{figure number|2}}Shingled geometries are common in certain depositional environments and can result in a number of isolated reservoir segments. However, this type of geometry is easy to overlook, and a layer-cake geometry is often erroneously imposed (from Sneider and Sneider).<ref name=Sneider2>Sneider, R. M., and J. S. Sneider, 2001, [http://archives.datapages.com/data/specpubs/memoir74/m74ch06/m74ch06.htm New oil in old places: The value of mature-field development], in M. W. Downey, J. C. Threet, and W. A. Morgan, eds., Petroleum provinces of the twenty-first century: [http://store.aapg.org/detail.aspx?id=77 AAPG Memoir 74], p. 63–84.</ref> Reprinted with permission from the AAPG.]]

[[File:M91FG197.JPG|thumb|300px|{{figure number|3}}High-frequency carbonate cycle on a meter scale from the Mississippian Madison Formation in the Wind River Basin of Wyoming (after Westphal et al., 2004). Reprinted with permission from the AAPG.]]

[[File:M91FG197.JPG|thumb|300px|{{figure number|3}}High-frequency carbonate cycle on a meter scale from the Mississippian Madison Formation in the Wind River Basin of Wyoming (after Westphal et al.).<ref>Westphal, H., G. P. Eberli, L. B. Smith, G. M. Grammer, and J. Kislak, 2004, [http://archives.datapages.com/data/bulletns/2004/04apr/0405/0405.HTM Reservoir characterization of the Mississippian Madison Formation, Wind River basin, Wyoming]: AAPG Bulletin, v. 88, no. 4, p. 405–432</ref> Reprinted with permission from the AAPG.]]

Carbonate sediments tend to show a ribbon-like geometry and are less commonly developed as widespread sheets. Examples of both geometries are shown by two of the major carbonate reservoir intervals in the Middle East (Ehrenberg et al., 2007). Sediments of the Permian–Triassic Khuff Formation were deposited on a very low relief shelf, sheltered from the open ocean by a barrier reef. These show a layer-cake geometry consisting of interbedded mudstones and fine-grained grainstones (Alsharhan, 2006). By contrast, sedimentation in the Jurassic Arab Formation occurred on a shelf differentiated into shallow shoals and intrashelf basins. These exhibit a progradational geometry (Meyer and Price, 1992).

Carbonate sediments tend to show a ribbon-like geometry and are less commonly developed as widespread sheets. Examples of both geometries are shown by two of the major carbonate reservoir intervals in the Middle East (Ehrenberg et al., 2007). Sediments of the Permian–Triassic Khuff Formation were deposited on a very low relief shelf, sheltered from the open ocean by a barrier reef. These show a layer-cake geometry consisting of interbedded mudstones and fine-grained grainstones (Alsharhan, 2006). By contrast, sedimentation in the Jurassic Arab Formation occurred on a shelf differentiated into shallow shoals and intrashelf basins. These exhibit a progradational geometry (Meyer and Price, 1992).