(a)
(b)
Figure 4: Comparison of helium (a) and ethane (b) pulse decay data for sample B5FD2A2. Mean pore pressure increases throughout the helium permeability measurement because the upstream reservoir of the permeameter is larger than the downstream reservoir, and gas was bled from the downstream reservoir to generate the differential pressure. Mean pore pressure increases by more in the ethane measurement than the helium measurement because liquid/semiliquid ethane desorbs to reach equilibrium at the final gas pressure, which is lower than the equilibrium gas pressure during the soak period (time < 0 on graphs). Differential pressure in the ethane permeability measurement takes more than twice as long to decay than the helium differential pressure because adsorbed liquid/semiliquid ethane constricts flow paths resulting in lower ethane gas permeability. Green lines indicate the difference between minimum mean pressure and final equilibrium pressure.