Open AccessPermeability of illite‐bearing shale: 2. Influence of fluid chemistry on flow and functionally connected pores
Author(s) -
Kwon Ohmyoung,
Herbert Bruce E.,
Kronenberg Andreas K.
Publication year - 2004
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004jb003055
Subject(s) - illite , permeability (electromagnetism) , saturation (graph theory) , oil shale , fluid dynamics , mineralogy , geology , chemistry , clay minerals , thermodynamics , paleontology , biochemistry , physics , mathematics , combinatorics , membrane
Bedding‐parallel permeability of illite‐rich shale of the Wilcox formation has been investigated using distilled water and 1 M solutions of NaCl, KCl, and CaCl 2 as pore fluids. Despite low modal concentrations of swelling clays, specimens expand upon fluid saturation and permeabilities depend on fluid composition. Permeabilities to flow of 1 M CaCl 2 are 3–5 times greater than values measured for the other pore fluids, suggesting sensitivity to exchange of divalent cations for monovalent cations at clay mineral surfaces. Permeabilities of individual samples exhibit nonrecoverable changes with sequential changes in composition of incoming fluid. Permeabilities k at varying effective pressure P e fit a cubic law k = k 0 [1 − ( P e / P 1 ) m ] 3 , where m and P 1 are independent of fluid composition, and k 0 is greater for transport of 1 M CaCl 2 than that for transport of the other pore fluids. Assuming that fluid conduits have crack‐like dimensions, the lack of sensitivity of m and P 1 to fluid composition suggests that surface roughness and asperity stiffness of conduits are unaffected by cation exchange, while changes in k 0 reflect changes in the clay‐fluid interfaces of the connected pore space.