Page 365 - Fundamentals of Reservoir Engineering
P. 365
NATURAL WATER INFLUX 300
aquifer to reservoir radius r eD = r e/r o, for radial aquifers. In contrast, plots of W D versus
t D for both radial and linear geometry and, in the former case, for select values of r eD
are included as figs. 9.3 - 9.7. The plots are taken from the published solutions of
1
equ. (7.18) by Hurst and van Everdingen . Each chart has a different resolution of the
dimensionless time scale. It should be noted that the graphs are valid for all values of
t D and hence are applicable for calculating both the early, unstable influx (infinite
aquifer case) and for the influx occurring once the aquifer boundary effects have been
felt. There are differences in the way in which the dimensionless time and aquifer
constant are calculated, dependent on the geometry. These are summarised in
figs. 9.1 and 9.2.
Water
Oil t = θ°
θ 360 °
r o
θ
= Radians
2 π
r e
Fig. 9.1 Radial aquifer geometry
Darcy Units Field Units
kt kt
t = 2 t = constant× 2 (9.7)
D
D
φµ cr 0 φµ cr 0
the constant = .000264 (t-hours)
= .00634 (t-days)
= 2.309 (t-years)
2
2
U = 2π fφhcr (cc/atm) U = 1.119 fφhcr (bbl/psi) (9.8)
o
o
Oil
h
Water
L
W
Fig. 9.2 Linear aquifer geometry