MULTI-SCALE CHARACTERIZIATION OF PORE STRUCTURE AND MASS TRANSPORT IN NATURAL ROCKS

Abstract

**Please note that the full text is embargoed until 02/01/2026** The mass transport process in porous natural rocks is notably influenced by the pore structure with both geometrical and topological attributes. Nevertheless, previous studies have not taken into consideration the sample size effect or the impact of diagenesis processes on petrophysical investigations of rocks, fluids, and rock-fluid interactions. Six rocks (one granodiorite, one limestone, two chalks, one mudstone, and one dolostone) with different extents of heterogeneity at six different particle sizes were studied to describe the effects of pore structure (especially connectivity) on mass transport. Thirteen geologically different rocks (two marbles, four fossiliferous limestones, six mudstones, and one sandstone) were studied to examine the influence of diagenesis on petrophysical parameters and the Archie's cementation factor (m). The methods applied for both studies were (i) porosity measurements of granular rocks, (ii) analyses of gas-phase diffusive transport in a bed of packed particles and intact rocks along with the development of a solid quartz method at six particle sizes to identify the intraparticle diffusion contribution, and (iii) batch sorption tests of multiple ions (anions and cations) using inductively coupled plasma-mass spectrometry. The granular porosity measurement results reveal that with decreasing particle sizes, the effective porosities for the “heterogenous” group of rocks (Grimsel granodiorite and Edwards limestone) increase, whereas the porosities of the “homogeneous” group (two Israel chalk samples, Japan mudstone, and Wyoming dolostone) remain roughly constant. Moreover, the batch sorption work displays a different affinity of rocks for various tracers in anionic and cationic forms. For Grimsel granodiorite, Japan mudstone, and Wyoming dolostone, the adsorption capacity of Sm3+ and Eu3+ increases as the particle size decreases. Cementation factor results show that diagenesis and microfractures could be root causes of various values of cementation factors in 13 natural rock samples. In general, this integrated research of grain size distribution, granular rock porosity, intraparticle diffusivity, ionic sorption capacity, and diagenetic pattern gives insights into the pore connectivity effect on both physical and chemical transport behaviors in different lithologies with different particle sizes.