perm

A unit used by petroleum engineers to express the permeability of a porous subsurface reservoir. (Sometimes cubic feet are used instead of barrels.)

$A fraction.. The numerator is flow, expressed in barrels, times distance in feet times viscosity in centipoises. The denominator is days times square feet times pressure in square inches.$

At 0°C, 1 perm is approximately 5.72135 × 10^-11 kilograms per newton-second; at 23°C, approximately 5.74525 × 10^-11 kilograms per newton-second.