Page 575 - Petrophysics
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542 PETROPHYSICS: RESERVOIR ROCK PROPERTIES
matching [29], The permeability is obtained from:
where (tAp’)R is obtained from the horizontal line of the pressure
derivative, which corresponds to the infinite acting radial flow regime.
The inter-porosity fluid transfer coefficient is given by:
42. 5h@ctr$ (t Ap’) min
’= ( qB, ) At-
where (t.AP’)- and At- are the coordinates of the minimum point, as
shown in Figure 8.28. The fracture storage ratio is given by:
where the dimensionless time corresponding to the minimum time,
tDmin, is calculated from:
(8.90)
At- is the time coordinate of the minimum point of the trough on the
pressure derivative curve. At- on the log-log plot of the derivative
curve is equivalent to Atinf on the semilog plot of pressure versus time.
Equation 8.89 is plotted in Figure 8.29. Curve fitting the points and
solving explicitly for o yields:
where
The fracture storage ratio o can be directly determined from Figure 8.30
or Equation 8.91.
EXAMPLE
Pressure tests in the first few wells located in a naturally fractured
reservoir yielded a similar average permeability of the system of 85 mD.
