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On the threshold of flow in a tight natural rock
Author(s) -
Meredith P. G.,
Main I. G.,
Clint O. C.,
Li L.
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl050649
Subject(s) - percolation threshold , porosity , permeability (electromagnetism) , scaling , materials science , porous medium , microstructure , percolation theory , radioactive waste , percolation (cognitive psychology) , effective porosity , geology , mineralogy , composite material , electrical resistivity and conductivity , conductivity , physics , chemistry , geometry , nuclear physics , biochemistry , mathematics , quantum mechanics , neuroscience , membrane , biology
The behaviour of hydraulically ‘tight’ barrier rocks is a key determinant of the long‐term integrity of potential underground storage sites for the waste products from low‐carbon emission energy production technologies (including nuclear waste and CO 2 captured from fossil fuels). Here we isolate the relationship between crack‐induced permeability and porosity using an initially crack‐free natural crystalline material. We vary secondary porosity from an initial value of zero, and demonstrate that the bulk permeability K varies with total connected porosity Φ above the percolation threshold Φ c as K = K 0 (Φ − Φ c ) n , where n = 3.8 ± 0.4, i.e., similar to results obtained for higher porosity rocks, indicating universality of this scaling law. Close to the percolation threshold a modest change in total porosity from 1% to 5% or so results in a massive change in permeability of 7 orders of magnitude or more. The results are consistent with a continuum percolation model that reflects the microstructure of the pore/induced microcrack network in the natural material.