Geology Reference
In-Depth Information
quantities determined by the geometry of the pores. The
m
parameter varies
between about 1.2 and 1.8 according to the shape of the matrix grains.
Archie's Law departures from linearity are small for common values of
porosity (Figure 5.2).
Figure 5.2
Variation, according to Archie's Law, of bulk resistivity,
,fora
rock with an insulating matrix and pore-water resistivity
ρ
w
. The index, m, is
about 1.2 for spherical grains and about 1.8 for platey or tabular materials.
ρ
