Changes

==Beach sandstones==

==Beach sandstones==

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 [[Figure 117]]).

[[File:M91FG117.JPG|thumb|300px|{{file 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|117]]

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]]).

==Tidal channels==

==Tidal channels==