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The permeability of a medium is related to the porosity, but also to the shapes of the pores in the medium and their level of connectedness. [2] Fluid flows can also be influenced in different lithological settings by brittle deformation of rocks in fault zones ; the mechanisms by which this occurs are the subject of fault zone hydrogeology . [ 3 ]
The movement of a fluid through porous media is described by the combination of Darcy's law with the principle of conservation of mass in order to express the capillary force or fluid velocity as a function of various other parameters including the effective pore radius, liquid viscosity or permeability. [3]
Connected porosity is more easily measured through the volume of gas or liquid that can flow into the rock, whereas fluids cannot access unconnected pores. Porosity is the ratio of pore volume to its total volume. Porosity is controlled by: rock type, pore distribution, cementation, diagenetic history and composition. Porosity is not controlled ...
Micro CT of porous medium: Pores of the porous medium shown as purple color and impermeable porous matrix shown as green-yellow color. Pore structure is a common term employed to characterize the porosity, pore size, pore size distribution, and pore morphology (such as pore shape, surface roughness, and tortuosity of pore channels) of a porous medium.
A porous medium is most often characterised by its porosity. Other properties of the medium (e.g. permeability , tensile strength , electrical conductivity , tortuosity ) can sometimes be derived from the respective properties of its constituents (solid matrix and fluid) and the media porosity and pores structure, but such a derivation is ...
With reference to the diagram to the right, the flow velocity is in SI units (/), and since the porosity φ is a nondimensional number, the Darcy flux , or discharge per unit area, is also defined in units (/); the permeability in units (), the dynamic viscosity in units () and the hydraulic gradient is in units (/).
In physics and engineering, permeation (also called imbuing) is the penetration of a permeate (a fluid such as a liquid, gas, or vapor) through a solid.It is directly related to the concentration gradient of the permeate, a material's intrinsic permeability, and the materials' mass diffusivity. [1]
In case of its absence, which is common in most cases, an estimate for permeability can be derived from empirical relationships with other measurements such as porosity, NMR and sonic logging. Darcy's law [10] is applied in the laboratory to measure the core plug permeability with an inert gas or liquid (i.e. that does not react with the rock). [6]