Page 459 - Petrophysics

LINEAR FLOW THROUGH FRACTURES AND CHANNELS 427

Figure 7.4. Linear model for fracturepow.

L = length of fracture, cm.
p = fluid viscosity, Poise.
Ap = pressure drop (p1 - p2), dynes/cm2.

The actual velocity of the fluid flowing through the fracture is thus:

(7.32)

Assuming that the porosity of the fracture is unity and the connate water
saturation within the fracture is zero, the actual velocity (according to
Darcy's law where Ap is expressed in dynes/cm2, k in Darcy, p in Poise,
and L in cm) is:

v = (9.869 x 1Op9kf)- AP (7.33)
PL

Combining Equations 7.32 and 7.33 and solving for the permeability of
the fracture kf (where wf = cm and kf = Darcy):

kf = 8.444 x 10'~: (7.34)

Fractures are classified as open (visible open space), closed (no visible
open space in thin section), partially filled, or completely filled [8].
Many carbonate reservoirs exhibit fractures with some degree of filling,
which may consist of crystals of calcite, dolomite, pyrite, gypsum, etc.
Precipitates from the leaching solution, which circulates through the
carbonate rock and deposits fine particles inside the fractures and vugs,