Permeability of porous media
Permeability describes how easily a fluid flows through a porous material such as sandstone, soil or a filter. It appears in Darcy’s law, which links flow rate to pressure gradient and fluid viscosity.
The SI unit is the square meter, but real materials have tiny values, so the petroleum and groundwater industries use the darcy. One darcy is about 0.987 × 10−12 m², very close to one square micrometer.
- Good oil reservoir sandstone: 100–1,000 mD
- Tight gas sand: below 0.1 mD
- Shale: nanodarcy range
- Clean gravel: above 100 D
This converter is for intrinsic (fluid) permeability, not magnetic permeability.