Open AccessEffects of pressure on pore characteristics and permeability of porous rocks as estimated from seismic wave velocities in cores from TCDP Hole‐A
Author(s) -
Kitamura Keigo,
Takahashi Miki,
Mizoguchi Kazuo,
Masuda Koji,
Ito Hisao,
Song ShengRong
Publication year - 2010
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2010.04694.x
Subject(s) - permeability (electromagnetism) , geology , porosity , overburden pressure , pore water pressure , mineralogy , silt , petrology , porous medium , crust , geotechnical engineering , soil science , geophysics , geomorphology , chemistry , biochemistry , membrane
SUMMARY Changes in V p / V s (Poisson's ratio) around a fault are related to changes in the fluid transport properties of rocks, which play a significant role in seismogenic processes. Here we report a notable relationship between V p / V s and the permeability of porous fault‐related rocks (Chelungpu fault, Taiwan) by direct and simultaneous measurement of elastic wave velocities ( V p and V s ) and permeability under increasing effective confining pressure ( P eff ) up to 25 MPa. V p and V s for all samples increased with P eff in the range up to 20 MPa, then were nearly constant as P eff increased to 25 MPa. Most silty sandstones with large proportions of fine‐grained material showed positive correlations between V p / V s and permeability with rising pressure. On the other hand, well‐sorted sandstones showed only slight changes in permeability with respect to V p / V s with rising pressure. We infer that grain size distributions, in particular the amount of silt‐ and clay‐size grains, are responsible for the change in permeability with pressure as small particles clog pore networks with increasing P eff , causing the decrease in permeability. These findings may be useful to explain changes in permeability and pore pressure in the deep crust.