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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.
A force balance equation known as Washburn's equation for the above material having cylindrical pores is given as: [1] ... Porosity; Wood's metal, ...
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.
Web-based porosity and permeability calculator given flow characteristics; Multiphase fluid flow in porous media; Florida Method of Test For Concrete Resistivity as an Electrical Indicator of its Permeability Archived 2011-06-16 at the Wayback Machine
where is the void ratio, is the porosity, V V is the volume of void-space (gases and liquids), V S is the volume of solids, and V T is the total (or bulk) volume. This figure is relevant in composites , in mining (particular with regard to the properties of tailings ), and in soil science .
Specific yield, also known as the drainable porosity, is a ratio, less than or equal to the effective porosity, indicating the volumetric fraction of the bulk aquifer volume that a given aquifer will yield when all the water is allowed to drain out of it under the forces of gravity: = where
For this reason, hydrocarbon-in-place can be expressed as a percentage of the total (gross) rock volume thereby bypassing the issue of porosity altogether. However, since current logging tools cannot directly sense hydrocarbon alone, the intermediate step of porosity calculation is still a basic necessity.
Gassmann fluid substitution requires that the porosity remain constant. The assumption being that, all other things being equal, different saturating fluids should not affect the porosity of the rock. This does not take into account diagenetic processes, such as cementation or dissolution, that vary with changing geochemical conditions in the ...