Changes

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.

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 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.

Barrier islands (Figure 3f) illustrate the spatial variability in facies that affect reservoir properties. Sands in the beach or foreshore are [[Core_description#Maturity|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.