Page 264 - Fundamentals of Reservoir Engineering

OILWELL TESTING 201

Closed-in time t +∆ t log t +∆ t p ws (psi)
∆t (hrs) t ∆ t ∆
0 4506(p wf)
.5 196.2 2.29 4675
.66 148.9 2.17 4705
1.0 98.6 1.99 4733
1.5 66.1 1.82 4750
2.0 49.8 1.70 4757
2.5 40.04 1.60 4761
3.0 33.53 1.52 4763
4.0 25.40 1.40 4766
6.0 17.27 1.24 4770
8.0 13.20 1.12 4773
10.0 10.76 1.03 4775
12.0 9.13 .96 4777
TABLE 7.6

The pressure buildup plot, on a linear scale, is shown as fig. 7.23. The last seven
t +∆ t
points define a straight line and the extrapolation of this trend to the value of = 0
t ∆
*
gives p = 4800 psi and, assuming the validity of equ. (7.54) for an initial well test,
p i = 4800 psi.

p (psi)
ws
4800 p*=4800
psi

=
ws
p (1 hr) x
4752 psi

4700 4700

4600 4600
2 1 0
t +∆t
log
∆t

Fig. 7.23 Horner buildup plot, infinite reservoir case