Page 220 - Fundamentals of Reservoir Engineering

OILWELL TESTING 158

EXERCISE 7.2 SOLUTION

1) The permeability and skin factor can be obtained by the analysis of the transient flow
period for which

qµ 4kt
p wf = p − 4kh ln γ φ µ cr w 2 + 2S
i
π
or in field units

162.6q B k
µ
p wf = p − kh o log t log φµ cr w 2 − 3.23 0.87S
+
+
i
Thus for the initial period, when transient flow conditions prevail, a plot of p wf versus
log t should be linear with slope m = 162.6 q µ B o /kh, from which kh and k can be
determined. Furthermore, using the value of p wf(1hr) taken from the linear trend for a
flowing time of one hour and solving explicitly for S gives

(p − p ) k
S 1.151 i wf(1hr) − log 2 + 3.23
=
m φµ cr w
The plot of p wf versus log t for the first few recorded pressures, fig. 7.4, indicates that

transient flow conditions last for about four hours and that the values of m and p wf(1 hr)
are 61 psi/log cycle and 2917 psia, respectively.