Capillary Condensation in a Fractal Porous Medium

Abstract

Small-angle x-ray and neutron scattering are used to characterize the surface roughness and porosity of a natural rock which are described over three decades in length scales and over nine decades in scattered intensities by a surface fractal dimension D = 2.68+/-0.03. When this porous medium is exposed to a vapor of a contrast-matched water, neutron scattering reveals that surface roughness disappears at small scales, where a Porod behavior typical of smooth interfaces is observed instead. Water-sorption measurements confirm that such interface smoothing is due predominantly to the water condensing in the most strongly curved asperities rather than covering the surface with a wetting film of uniform thickness.

Angstrom-to-millimeter characterization of sedimentary rock microstructure

“…From these results we conclude that the proposed multiscale statistical-geometric description furnishes useful and unifying insights into the pore-size distribution, porosity, and correlation function and the characteristic length scales for capillary pressure, nuclear spin relaxation, and flow permeability. The proposed method may find use in the characterization of other materials exhibiting broad pore-size distributions, such as carbonate rocks, soil, cements, and concretes and should be a useful complement to alternative techniques, which rely on solid-fluid interactions for pore structure characterization [40,41]. The method may also provide detailed input data (two-point correlation functions) for the computer reconstruction [42,43] of the microstructure of porous rock and other materials exhibiting both fractal and Euclidean characteristics.…”

Application of SAXS and SANS in evaluation of porosity, pore size distribution and surface area of coal

“…In general, it is feasible to perform SAXS and SANS studies on coal saturated with various sorbates and then conjecture both about the mechanisms of sorption and the microstructural modification of coal matrix by sorbents. An example of such work in a related field (water sorption in sandstones) is given in Broseta et al (2001).…”

Statistical Synthesis of Imaging and Porosimetry Data for the Characterization of Microstructure and Transport Properties of Sandstones

“…Deconvolution of MIP data is complex and requires independent information on the size distribution, spatial order and interconnectedness of the pores (Tsakiroglou and Payatakes 2000;Tsakiroglou et al 2009). Gas or vapour adsorption/condensation methods are unable to probe the entire range of pore length scales within sedimentary rocks, but have been used to establish the fractal characteristics of the solid-void interface in a manner consistent with SANS/SAXS measurements (Broseta et al 2001). Finally, attempts to obtain the pore size distribution by analyzing the NMR relaxation dynamics of fluid-saturated samples have been met with variable success, depending on the approach taken (Dunn et al 2002;Song et al 2000).…”