In Petrophysics a Klinkenberg correction is a procedure for calibration of permeability data obtained from a minipermeameter device.
This takes place when the pore space approaches the mean free path of the gas Under steady state and laminar flow condition, Klinkenberg[1] demonstrated that the permeability of porous media to gases is approximately a linear function of the reciprocal pressure.
However, Klinkenberg's formulation ignores the transition flow region, where neither molecule-molecule nor molecule-wall interactions can be neglected because both are playing a relevant role.
The pressure drop across the sample and the flow rate are measured and permeability is calculated using Darcy's law.
Gas slippage will occur during the measurement because nitrogen is injected quickly from probe to core and it is very difficult to get to equilibrium in very short time span.