Changes

==Shoreface sands form layer-cake geometries==

==Shoreface sands form layer-cake geometries==

Shoreface sands prograde by lateral accretion with a tendency to produce layer-cake tabular geometries. Depositional dead ends are rare within individual shoreface sandstones, and sweep efficiencies are generally high as a result; for example, Tyler and Ambrose<ref>Tyler, N., and W. A. Ambrose, 1986, Facies architecture and production characteristics of strand-plain reservoirs in North Markham-North Bay City field, Frio Formation, Texas: AAPG Bulletin, v. 70, no. 7, p. 809–829.</ref> described excellent continuity and efficient simple sweep in the Carlson shoreface reservoir of the North Markham-North City Bay field of Texas. The large size and excellent lateral continuity of shoreface reservoirs give a reasonable chance that these systems will be in contact with an aquifer (Table 29).

Shoreface sands prograde by lateral accretion with a tendency to produce layer-cake tabular geometries. Depositional dead ends are rare within individual shoreface sandstones, and sweep efficiencies are generally high as a result; for example, Tyler and Ambrose<ref name=TA1986>Tyler, N., and W. A. Ambrose, 1986, Facies architecture and production characteristics of strand-plain reservoirs in North Markham-North Bay City field, Frio Formation, Texas: AAPG Bulletin, v. 70, no. 7, p. 809–829.</ref> described excellent continuity and efficient simple sweep in the Carlson shoreface reservoir of the North Markham-North City Bay field of Texas. The large size and excellent lateral continuity of shoreface reservoirs give a reasonable chance that these systems will be in contact with an aquifer (Table 29).

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==Beach sandstones==

==Beach sandstones==

[[File:M91FG117.JPG|thumb|300px|{{figure number|6}}Time series of water cut maps from the West Cornelius reservoir, North Markham-North Bay City field, Texas. In this strand-plain reservoir, east-northeastndashwest-southwest-oriented beach ridge macroforms are fairways for water ingress. Tidal mud flat deposits south of the field restrict water influx from this direction (from Tyler and Ambrose, 1986). Reprinted with permission from the AAPG.]]

[[File:M91FG117.JPG|thumb|300px|{{figure number|6}}Time series of water cut maps from the West Cornelius reservoir, North Markham-North Bay City field, Texas. In this strand-plain reservoir, east-northeastndashwest-southwest-oriented beach ridge macroforms are fairways for water ingress. Tidal mud flat deposits south of the field restrict water influx from this direction (from Tyler and Ambrose, reprinted with permission from the AAPG.<ref name=TA1986 />)]]

Beach sandstones form as single belts or accrete laterally to form strand plains many kilometers long and several kilometers wide. Modern strand plains such as the Nayarit strand plain of western Mexico show a ridge and swale topography on their surfaces (McCubbin, 1982). Mud fills in the interridge swales can act as permeability barriers to lateral flow in the subsurface. One example in the Frio Formation of south Texas is known to have caused the compartmentalization of a beach ridge interval containing several million barrels of recoverable oil (Reistroffer and Tyler, 1991). Water ingress may preferentially occur along the low-lying swales (Tyler and Ambrose, 1986) (see also [[:File:M91FG117.JPG|Figure 6]]).

Beach sandstones form as single belts or accrete laterally to form strand plains many kilometers long and several kilometers wide. Modern strand plains such as the Nayarit strand plain of western Mexico show a ridge and swale topography on their surfaces (McCubbin, 1982). Mud fills in the interridge swales can act as permeability barriers to lateral flow in the subsurface. One example in the Frio Formation of south Texas is known to have caused the compartmentalization of a beach ridge interval containing several million barrels of recoverable oil (Reistroffer and Tyler, 1991). Water ingress may preferentially occur along the low-lying swales<ref name=TA1986 /> ([[:File:M91FG117.JPG|Figure 6]]).

==Tidal channels==

==Tidal channels==