Mercury cyclic porosimetry: Measuring pore-size distributions corrected for both pore-space accessivity and contact-angle hysteresis

Abstract

We propose a set of simple formulae for interpreting "mercury cyclic porosimetry" measurements where multiple intrusion-extrusion cycles are carried out. By employing two parameters α∈[0,1] and κ∈[0,1], our theory quantitatively breaks down any hysteresis observed in cyclic porosimetry data into contributions due to connectivity effects and contact-angle hysteresis, respectively. In particular, the parameter α, called "pore-space accessivity", characterizes any serial connectivity between different-size pores. It has long been recognized that the standard method for determining the pore-size distribution (PSD) from mercury intrusion data based on the capillary bundle assumption overestimates the fraction of smaller pores; that corresponds to the α→1 limit of our model. In contrast, for materials with α<1, our theory predicts a broadened PSD shifted toward larger radii, thus representing a simple way of rectifying PSDs for connectivity effects. The proposed model also establishes mercury cyclic porosimetry as a standard experimental procedure for measuring α, which can then be used in continuum models of porous media where connectivity effects play a significant role, such as in multiphase flow.

Keywords: Accessivity connectivity; Hysteresis; Mercury porosimetry; Pore-size distribution; Porous media.