Page 298 - Fundamentals of Reservoir Engineering

OILWELL TESTING 234

∆p
(psi)
1
1 -
Ct ∆

C= 1.7
1500
C= 2.1
C= 2.5

1400

1300
0 .5 1.0
log t ∆

Fig. 7.43 Russell afterflow analysis Exercise 7.9)

The value of (p ws (∆t) - p wf (t))/(1−1/C∆t) at ∆t = 1 hour can be read from the linear plot
as 1329 psi. Therefore the skin factor can be calculated using equ. (7.79) as

1329 19.4
S = 1.151 − log − 6 + 3.23 = 4.7
×
×
×
151 .2 .6 20 10 × .09
2) McKinley Analysis

To apply the McKinley method it is necessary to plot the closed in time ∆t(minutes)
versus the pressure buildup ∆p= p w, (∆t)−p wf (t) (psi) on transparent paper using the
same log-log scales as on the McKinley type curve chart. When this plot is moved
laterally across the McKinley chart, keeping the abscissae of both charts together, the
early part of the buildup is found to match the type-curve which has the parametric
value T/F = 2500, fig. 7.44. Selecting a match point ∆t = 60 minutes, ∆p = 750 psi, the
corresponding value on the abscissa of the McKinley chart is ∆pF/q = 0.14. Therefore,