# Dictionary:Permeability

(pur mē ∂ bil’ i tē)

**1**. The ratio of the magnetic field **B** to the magnetizing force **H.
**

**2**. A measure of the ease with which a fluid can pass through the pore spaces of a formation. Measured in millidarcy (1/1000 darcy) units. The permeability constant *k* is expressed by **Darcy’s law** as μ*q*/(d'**p'**/d*x*), where μ is fluid viscosity, *q* is linear rate of flow, and *d'***p'**/*dx* is the hydraulic pressure gradient. The presence of one fluid can change the **effective permeability** to another fluid, so that in multiphase flow the effective permeabilities of the component fluids may not add to the total permeability. See Figure P-1.

## References

- ↑ Best, M. E.; Katsube, T. J. (1995). "Shale permeability and its significance in hydrocarbon exploration".
*The Leading Edge***14**(3): 165–170. doi:10.1190/1.1437104.