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Dynamic Data Analysis – v5.12.01 - © KAPPA 1988-2017
Chapter
3 – P ressure Transient Analysis (PTA)- p65/743
3.B.4
Shut-in after a complex production and superposition plot
When a shut-in follows a complex production / injection history, the process is equivalent to
that for a simple build-up, but the Horner time must be replaced by the superposition time
function defined by:
t
t
t t
q q
q q
t Sn
i
n
n
i
n
n
i
i
log )
log(
1
1
1
1
A plot of pressure versus superposition time is the ‘general semi-log’ plot:
Fig. 3.B.4 – General semilog: superposition plot
Calculations of permeability is the same as for the Horner plot, and the skin factor is calculated
by taking one point on the straight line, say (X,Y), and is given by:
n
i
i
n
in
n
i
i
wt
wf
t
t
q q
q q
rc
k
X
m
p Y
S
1
1
1
2
23.3
log
log
151 .1