Changes

===Shoreline deposits===

===Shoreline deposits===

In shoreline systems adjacent to active deltas, the geometry and internal anatomy of sandstone bodies are controlled by an interplay of tidal and wave processes. Clastic, nondeltaic shorelines with a tidal range of 0–2 m (microtidal) tend to be wave-dominated. Resulting sand bodies are elongate barrier islands and strandplains. A tidal range of 2–4 m (mesotidal) tends to produce short (“drum stick”) barrier islands with extensive tidal flats and ebb tidal deltas. A tidal range of 4–6 m (macrotidal) tends to produce estuarine linear tidal sand ridges that are perpendicular to shoreline with associated extensive tidal flats.

In shoreline systems adjacent to active deltas, the geometry and internal anatomy of sandstone bodies are controlled by an interplay of tidal and wave processes. Clastic, nondeltaic shorelines with a tidal range of 0–2 m (microtidal) tend to be wave-dominated. Resulting sand bodies are elongate [[barrier islands]] and [[strandplain]]. A tidal range of 2–4 m (mesotidal) tends to produce short (“drum stick”) barrier islands with extensive [[tidal flats]] and [[ebb tidal deltas]]. A tidal range of 4–6 m (macrotidal) tends to produce [[Estuaries|estuarine]] linear tidal sand ridges that are perpendicular to shoreline with associated extensive [[tidal flat]]s.

Barrier islands (Figure 3f) illustrate the spatial variability in facies that affect reservoir properties. Sands in the beach or foreshore are very well sorted, lack interstratified clay, and exhibit excellent reservoir properties where not cemented. Tidal inlet and flood tidal delta deposits comprise another important grouping of reservoir quality rocks, particularly because they are most often preserved in the rock record.

Barrier islands (Figure 3f) illustrate the spatial variability in facies that affect reservoir properties. Sands in the beach or foreshore are very well sorted, lack interstratified clay, and exhibit excellent reservoir properties where not cemented. [[Tidal inlets|Tidal inle]]t and [[Flood tidal deltas|flood tidal delta]] deposits comprise another important grouping of reservoir quality rocks, particularly because they are most often preserved in the rock record.

Wireline log shapes through barrier island sequences vary depending on exactly where a well intersects the barrier island complex. [[Basic open hole tools#Gamma ray|Gamma ray]], [[Basic open hole tools#Spontaneous potential|SP]], and [[Basic open hole tools#Resistivity|resistivity]] logs through the barrier core have an upward-coarsening motif (Figure 3f). Logs through the back barrier and lower shoreface are typically highly serrate and often lack a well-defined upward-coarsening motif. Logs through the barrier inlet may exhibit upward fining.

Wireline log shapes through barrier island sequences vary depending on exactly where a well intersects the barrier island complex. [[Basic open hole tools#Gamma ray|Gamma ray]], [[Basic open hole tools#Spontaneous potential|SP]], and [[Basic open hole tools#Resistivity|resistivity]] logs through the barrier core have an upward-coarsening motif (Figure 3f). Logs through the [[back barrier]] and [[lower shoreface]] are typically highly serrate and often lack a well-defined upward-coarsening motif. Logs through the [[barrier inlet]] may exhibit upward fining.

In general, barrier islands have the best reservoir quality rocks at the top of the sequence. [[Reservoir quality]] drops off as one moves either seaward down the foreshore and shoreface into muds of the marine shelf or landward into the lagoon. High reservoir quality is also developed within the tidal inlet sandstones. Two major trends in directional permeability are suggested by (1) the shore-parallel nature of foreshore and shoreface sandstones and (2) shore-perpendicular tidal inlet and delta sandstones. In coastlines dominated by tidal processes, extensive interbedded mud and sand “flats” occur in the intertidal area of the coast and sand bars in estuarine channels in the subtidal area. The reservoir quality of tidal flat environments varies as a function of sand to mud ratio of the deposits. Reservoir quality of estuarine channel deposits also varies as a function of sand to mud ratio and degree of [[bioturbation]].

In general, barrier islands have the best reservoir quality rocks at the top of the sequence. [[Reservoir quality]] drops off as one moves either seaward down the [[foreshore]] and [[shoreface]] into muds of the marine [[shelf]] or landward into the [Lagoons|[lagoon]]. High reservoir quality is also developed within the tidal inlet sandstones. Two major trends in directional permeability are suggested by (1) the shore-parallel nature of foreshore and shoreface sandstones and (2) shore-perpendicular tidal inlet and delta sandstones. In coastlines dominated by tidal processes, extensive interbedded mud and sand “flats” occur in the intertidal area of the coast and sand bars in estuarine channels in the [[subtidal]] area. The reservoir quality of tidal flat environments varies as a function of sand to mud ratio of the deposits. Reservoir quality of estuarine channel deposits also varies as a function of sand to mud ratio and degree of [[bioturbation]].

===Shallow marine clastic deposits===

===Shallow marine clastic deposits===