  The prediction of permeability (i.e., apparent permeability) for the shale
gas is challenging due to the Klinkenberg slippage effect that depends on the
pore size and gas pressure. A recent Monte Carlo molecular simulation method
(i.e., DSBGK method) is employed to accurately compute the permeability by the
pore-scale simulations at different pressures. The computed results of a
benchmark problem proposed here are used to verify the accuracy of the simple
Klinkenberg correlation model, which relates the permeability to the intrinsic
permeability (i.e., liquid permeability) and pressure. The verification shows
that the Klinkenberg correlation model as a fitting formula is appropriate for
the industry applications since the relative error is small in the whole range
of the flow regime as long as it has been calibrated for each particular rock
sample at the two ends with low and high pressures, respectively, by
determining the model parameters using accurate permeability data that can be
obtained by the scheme presented herein.
