Page 464 - Petrophysics
P. 464
432 PETROPHYSICS: RESERVOIR ROCK PROPERTIES
fluid flowing through a capillary tube of radius r, and length L is:
(7.46)
From Darcy's law, assuming the channel porosity, @,, and the irreducible
water saturation, Siwc, are equal to unity and zero, respectively, the flow
rate is equal to:
2 *P
q = 9.369 x 10-9~rck- (7.47)
PL
Equating Equations 7.46 and 7.47, and solving for the permeability of the
solution channel yields:
l~ = 12.6 x 106rc2 (7.48)
where: k, = solution channel permeability, Darcy.
rc = radius of tubular channel, cm.
Porosity development in some carbonate reservoirs is due to leaching of
carbonate rocks by mineralizing waters. Precipitates from this circulating
water may be responsible for filling previously existing pores and
channels with a variety of fine particles (salt, chert, anhydrite, and
gypsum), making the porosity of the solution channel less than unity
[8,15]. Furthermore, the water saturation in these channels, which
formed due to circulating water, is unlikely to be zero. Thus, the actual
area open to flow is:
and Equation 7.48 becomes:
k, = 12.6 x 106(1 - SiwJ @c r: (7.50)
where: @, = solution channel porosity.
Siwc = irreducible water saturation in the channel.
The average permeability of a channel-matrix flow system can be
calculated from the Equation [ 131 :
