Page 136 - Petrophysics 2E
P. 136
PERMEABILITY-POROSITY RELATIONSHIPS 109
Equation 3.14 can be written as:
Substituting for svP from Equation 3.18 yields:
After the specific surface area per unit of pore volume, svP, is determined
from capillary data or petrographic image analysis (PIA), then Equation
3.17 is used to obtain svg.
EXAMPLE
A core sample from a uniform sandstone formation has a permeability
of 480 mD and a porosity of 0.17. Estimate:
(a) the average pore throat radius of the core;
(b) specific surface areas svP and SV~.
SOLUTION
(a) Assuming the flow channels in the core sample may be represented
by a bundle of capillary tubes, the pore throat radius can be estimated
from Equation 3.14. First, the permeability is converted from mD to pm2:
k = (480)(9.8717 x lo-*) = 0.4738pm2
Solving Equation 3.14 for r:
0.5
r= ( 0.17 ) = 4.72 pm or 4.72 x lo-* cm
8(0’4738)