Permeability (of a reservoir rock):

The ability of a rock to transmit fluid through the pore spaces.

- a key influence on the rate of flow, movement and drainage of the fluids.

There is no necessary relation between porosity and permeability.

A rock may be highly porous and yet impermeable if there is no communication between pores.

A highly porous sand is usually highly permeable.

A measure of the ease with which a fluid flows through the connecting pore spaces of rock or cement.

The unit of measurement is the millidarcy.

Fluid conductivity of a porous medium.

Ability of a fluid to flow within the interconnected pore network of a porous medium.