Darcy:
N:a unit of measure of permeability.A porous medium has a permeability of 1 darcy when differential pressure of 1 atmosphere across a sample 1 centimeter long and 1 square centimeter in cross section will force a liquid of 1 centipoise of viscosity through the sample at the rate of 1 cubic centimeter per second.
The permeability of reservoir rocks is usually so low that it is measured in millidarcys.
