Page 374 - Fundamentals of Reservoir Engineering

NATURAL WATER INFLUX 309
p i

p 0
p
1
p 1
p 1
p 2
p 2
p 2
p 3

PRESSURE p 3

0 t t t TIME
1 2 3
Fig. 9.9 Matching a continuous pressure decline at the reservoir-aquifer boundary by
a series of discrete pressure steps

Suppose that the observed reservoir pressures, which are assumed to be equal to the
pressures at the original hydrocarbon-water contact, are p i, p 1, p 2, p 3 .... etc., at times 0,
t 1, t 2, t 3 .... etc. Then the average pressure levels during the time intervals should be
drawn in such a way that

p + p 1
i
p =
1
2
p + p 2
1
p =
2
2
(9.15)

p + p
−
p = j 1 j
j
2
The pressure drops occurring at times 0, t 1, t 2 . . . etc. are then