Well-sorted

Poorly sorted sediments comprise very different particle sizes, resulting in a dense rock fabric wifh low porosify. As a resulf the connate water saturation is high, leaving little space for the storage of hydrocarbons. Conversely, a very well sorted sediment will have a large volume of space between the evenly sized components, a lower connate water saturation and hence a larger capacity to store hydrocarbons. Connate water is the water which remains in the pore space after the entry of hydrocarbons. 

Shelf (elastics) Sheet-like sandbodies resulting from storms or transgression. Usually thin but very continuous sands, well sorted and coarse between marine clays. Very high productivity but high quality sands may act as thief zones during water or gas injection. Action of sediment burrowing organisms may impact on reservoir quality. 

The area of actual erg and dune formation is delimited by the 150 mm/yr isohyet. This precipitation boundary appears to have shifted strongly in the recent past. Between 20,000 and 13,000 yr BP, the southern limit of active dune formation in the Sahara desert was 800 km south of its present position and most of the now sparely vegetated Sahelian zone was an area of active dune formation at that time. These dunes, mostly of the longitudinal type, are now fixed by vegetation, but their aeolian parentage is still obvious from their well-sorted material. A similar story can be told for the Kalahari sands. Overgrazing in recent times has reactivated aeolian transport in many regions with sands. 

Loess is a well-sorted, usually calcareous, non-stratified, yellowish-grey, aeolian clastic sediment. It consists predominantly of silt-sized particles (2-50 mm), and contains normally less than 20 percent clay and less than 15 percent sand. It covers the land surface as a blanket, which is less than 8 meters thick in the Netherlands (exceptionally 17 meters) but can reach up to 40 meters in Eastern Europe and 330 meters in China. 

Fine to medium grained sandstone,well sorted... 

Relatively high permeability, coarse-grained, and well-sorted sandy soils with occasional shells. These soils were interpreted to be deposited in a fluvial tidal channel axis or deltaic reworked distributary mouth bar deposits. 

Well-sorted sediments Sediments composed of one size class of particles, e.g., a deep-sea clay. 

The detrital material is most frequently semi rounded and well sorted. It is rather loosely arranged in the arenites - the indicator of grain contacts in the sediment may be estimated at about 2.0. Point contacts are few, or absent in the wackes. 

The aquifer material was a silica beach sand from the Columbia River basin in Oregon. The well-sorted sand had less than 1% by weight of... 

The term sorting describes the relative amounts of different grain sizes in a rock. A well-sorted sandstone will contain only sand-sized grains, while a poorly sorted sandstone will include a large percentage of silt, clay or larger grains. 

There are a few other terms commonly used to describe sandstones. A wacke is a poorly sorted sandstone containing more than 10% argillaceous material (clay). Arenites are well-sorted sandstones having little or no clay in them. An arkose is a sandstone whose particles are derived from plutonic rocks and so consist largely of quartz and feldspar. 

Below Unit B a silty sand layer (Unit C) was encountered in the cores taken between the mouth of the Great Wadi and the center of the Kom el Ahmr. Unit C contained a sequence of Old Kingdom to late Predynastic artifacts dating from about 2500 B.C. to 3200 B.C. Below Unit C, a very compact, well-sorted thick layer of Nile clay and sand was encountered (Unit N). No cores or trenches reached below this sedimentary deposit. Unit N contained occasional Predynastic ceramic and flint artifacts. Samples were collected from each 10-15-cm auger cut within each sedimentary unit in each core or trench. In addition, numerous samples of the Neonile deposits and other sediments from the nearby low desert and Great Wadi were taken for analysis. 

Coarse, well-sorted (i.e., the soil grains are all about the same size) sands and gravels are easier for water to flow through and hence form the most highly water-conductive materials (Fig. 3-3). The ease with which water is conducted through porous material is described by the parameter hydraulic conductivity, K, discussed further in Section 3.2.1. Hydraulic conductivity is primarily dependent on the characteristics of the porous material, but also is influenced by changes in the viscosity of water, which varies slightly with temperature. 

FIGURE 3-3 Particle size, size distribution, and hydraulic conductivity in soil. In a well-sorted soil, all the particles are similar in size, giving the soil a relatively high hydraulic conductivity compared with an otherwise similar but poorly sorted soil, in which small soil particles block the pore spaces between larger particles, thereby decreasing the hydraulic conductivity. 

In Fig. 11 three categories of sandstones ( clean , calcareous and biogenic ) are separated depending on their original composition. The term clean sandstone is used for well sorted quartz sandstones with a phyllosilicate content below ca. 20%. Calcareous has been used for sandstones with similar textures in which carbonate grains dominate above, for instance,... 

The Red Wildmoor sandstone is a Lower-Triassic, fine-grained and well sorted sandstone. The mineralogy is dominated by 74% quartz with some feldspar (14%) and 12% clay minerals. The average porosity... 

Well-sorted sands -3 to -5 Poorly-sorted sand gravel 25 to 40... 

EC Cross-stratified aeolian dune bodies Trough cross-bedded sand (Ste) planar laminated sand (Spe) low angle cross-bedded sand (Sle) horizontally laminated sand (She) ripple cross-laminated sand (Sre) massive sand (Sme) Tabular, lenticular and wedge-shaped 1-3 m thick > 1 km lateral extent Fine to lower coarse, moderately to well sorted sand/sandstone Scattered ovoid to elongate concretions and small type 1 and type 3 phreatic tabular units... 

The sandstones are well sorted and have a variable carbonate grain content (0-45% of the framework grains). The grain size decreases from medium... 

The Namorado Sandstone is composed of fine- to medium-grained, moderately to well sorted arkoses and subarkoses (Fig. 5). The main framework constituents are quartz, potassium feldspar, plagioclase and quartz-feldspar rich rock fragments, most of Plutonic origin. Although previous work indicated the predominance of K-feldspars (Carvalho, 1990 ... 

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