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The Norphlet Formation (Upper Jurassic) of the central and eastern Gulf of Mexico regions accumulated under arid climatic conditions. Norphlet paleogeography in southwestern and offshore Alabama and the Florida Panhandle was dominated by a broad desert plain rimmed to the north and east by the Appalachian Mountains and to the south by a developing shallow sea. The desert plain extended westward into eastern and central Mississippi. Quartzose sandstones were deposited as dune and interdune sediments. The source of the sand was adjacent and updip alluvial-fan, plain, and wadi deposits. Wadi and playa-lake sediments also accumulated in the interdune areas. A marine transgression was initiated during upper Norphlet deposition resulting in the reworking of previously deposited sediments.
Petroleum reservoir rocks consist primarily of quartzose sandstones that are eolian dune, wadi, and marine in origin. The high-angle (up to 30°) cross-bedded eolian sandstones are moderately well-sorted to well-sorted
subarkoses having subrounded to rounded quartz grains. The dune and interdune sandstones are interbedded with wadi and playa-lake deposits having wavy discontinuous laminae. These water-deposited sandstones are not as texturally mature as the dune sandstones. The upper part of the Norphlet includes massively bedded to horizontal laminated marine sandstones. Porosity is principally secondary dissolution with some intergranular porosity. The secondary porosity is a result of decementation of anhydrite and/or calcite and by grain dissolution. Porosity in the marine sandstones is reduced through calcite cementation in downdip areas. The Permian eolian dune and wadi sandstone reservoirs in the Viking field, North Sea, can be used as analogs for anticipating reservoir performance for the No phlet sandstones.
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