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Estimate of transport properties of porous media by microfocus X‐ray computed tomography and random walk simulation
Author(s) -
Nakashima Yoshito,
Watanabe Yoshinori
Publication year - 2002
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2001wr000937
Subject(s) - porosity , random walk , permeability (electromagnetism) , porous medium , materials science , voxel , diffusion , volume (thermodynamics) , representative elementary volume , effective diffusion coefficient , tomography , mathematics , optics , chemistry , magnetic resonance imaging , physics , composite material , computer science , thermodynamics , microstructure , statistics , medicine , biochemistry , radiology , artificial intelligence , membrane
The transport properties (porosity, surface‐to‐volume ratio of the pore space, diffusion coefficient, and permeability) of a porous medium were calculated by image analysis and random walk simulation using the digital image data on the pore structure of a bead pack (diameter 2.11 mm). A theory developed for laboratory experiments of nuclear magnetic resonance was applied to the random walk simulation. The three‐dimensional data set (256 3 voxels) of the bead pack was obtained by microfocus X‐ray computed tomography at a spatial resolution of 0.053 mm. An original cluster labeling program, Kai3D.m, was used to estimate the porosity and surface‐to‐volume ratio. The surface‐to‐volume ratio and diffusion coefficient were calculated by an original random walk program, RW3D.m. The calculations were completed on a personal computer in reasonable time (≤13 hours). The permeability was estimated by substituting the results of Kai3D.m and RW3D.m into the Kozeny‐Carman equation. The results for the porosity, surface‐to‐volume ratio, and diffusion coefficient were within 5–8% of measured values, whereas the calculated permeability involved an error of 35%. The promising results of the present study indicate that it is possible to estimate the permeability of porous media with reasonable accuracy by the diffusometry and random walk simulation. Because, in principle, the diffusometry could be performed by proton nuclear magnetic resonance logging, the method of estimating the transport properties presented here is applicable to the in situ measurement of strata. We open the original Mathematica ® programs (Kai3D.m and RW3D.m) used to calculate the porosity, surface‐to‐volume ratio, and diffusion coefficient at the authors' home page to facilitate the personal‐computer‐based study of porous media using X‐ray computed tomography.