Page 296 - Fundamentals of Reservoir Engineering

OILWELL TESTING 232

∆t (mins) p ws (psi) ∆t (mins) p ws (psi)

0 1600 (p wf)
20 1920 270 2879
40 2160 300 2900
60 2350 360 2935
90 2525 420 2960
120 2650 480 2980
150 2726 540 2998
180 2779 600 3011
210 2822 660 3022
240 2852 720 3035
TABLE 7.17

t +∆ t
The conventional Horner plot of p ws versus log does not become linear, even for
t ∆
the largest values of ∆t, and therefore the afterflow analysis techniques presented in
this section must be used to analyse this test.

1) Evaluate k and S using the Russell method.

2) Determine the permeability in the vicinity of the wellbore and of the undamaged
formation using the McKinley method.

EXERCISE 7.9 SOLUTION

1) Russell Analysis

As suggested by Russell, the analysis should only be applied for pressures measured
after ∆t = 1 hour. In table 7.18 several values of the parameter C have been selected in
an attempt to linearize the plot of equ. (7.77).