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The porosity is a measure of the total pore space in the soil. This is defined as a fraction of volume often given in percent. The amount of porosity in a soil depends on the minerals that make up the soil and on the amount of sorting occurring within the soil structure.
The SI unit for permeability is the square metre (m 2).A practical unit for permeability is the darcy (d), or more commonly the millidarcy (md) (1 d ≈ 10 −12 m 2). The name honors the French Engineer Henry Darcy who first described the flow of water through sand filters for potable water supply.
Porosity is a fraction between 0 and 1, typically ranging from less than 0.005 for solid granite to more than 0.5 for peat and clay. The porosity of a rock, or sedimentary layer, is an important consideration when attempting to evaluate the potential volume of water or hydrocarbons it may contain.
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Porosity that is not considered "effective porosity" includes water bound to clay particles (known as bound water) and isolated "vuggy" porosity (vugs not connected to other pores, or dead-end pores). The effective porosity is of great importance in considering the suitability of rocks or sediments as oil or gas reservoirs, or as aquifers.
The porosity of a soil is an important factor that determines the amount of water a soil can hold, how much air it can hold, and subsequently how well plant roots can grow within the soil. [14] Soil porosity is complex. Traditional models regard porosity as continuous. This fails to account for anomalous features and produces only approximate ...
Comparing this distance to the straight-line distance shows that the tortuosity is about 1.5 for this sample. It has been demonstrated that the tortuosity increases when the porosity decreases. [10] Usually subjective estimation is used. However, several ways to adapt methods estimating tortuosity in 2-D have also been tried.
Many relationships between travel time and porosity have been proposed, the most commonly accepted is the Wyllie time-average equation. The equation basically holds that the total travel time recorded on the log is the sum of the time the sonic wave spends travelling the solid part of the rock, called the rock matrix and the time spent travelling through the fluids in the pores.