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Dynamic Data Analysis – v5.12.01 - © KAPPA 1988-2017
Chapte
r 2 – T heory- p48/743
2.H.4
Conclusions
2.H.4.a
on this series of designs
Beyond the arbitrary split between input and output parameters set in the methodology of
Pressure Transient Analysis, we see that several groups of parameters govern the response of
the well / reservoir system.
Pure wellbore storage: The absolute position of the early time unit slope is only a function
of the wellbore storage C.
Transition from pure wellbore storage to IARF: The shape of the hump, which originally
was set to C
D
e
2.Skin
when dealing with type curves, is actually a function of C and r
w
e
-Skin
,
and is also slightly affected by
and c
t
. The whole curve is translated along the unit slope
as a function of k,
and h, the governing group being kh/
.
IARF: The governing group is kh/
defining the semilog slope, hence the level of the
derivative stabilization when IARF is reached.
There is a residual effect of rw, skin,
and c
t
that defines the constant term of the IARF
straight line. Generally the Skin factor is calculated from this constant term.
At late time the parameters that govern the position of the PSS unit slope are r
e
,
, c
t
and
h. The governing group is
.c
t
.h.r
e
². You may actually prefer the group 2
.r
e
².h.
.c
t
, and
you get V
pore
.c
t
, where V
pore
is the reservoir pore volume. What we arrived at here is
nothing more than material balance.
There is a residual effect of all factors that affected the transient diffusion before PSS was
reached, and which constitute the constant term of the PSS straight line.
2.H.4.b
on the equations
If we consider the IARF equation given in previous section:
Skin
rc
k
t
kh
qB
p tp
wt
i
.
8686 .0 228 .3
log
log
6. 162
2
…and if we re-shuffle it a bit, we get:
Skin
w
t
er
ch
kh
t
kh
qB
tp
log2 228 .3
log
log
log
6. 162
One can see that the slope is a function of kh/
, and that there is a constant term that shows,
among other things, the residual effect of r
w
e
-Skin
,
and c
t
.
If we consider the PSS equation given previously:
Skin
rC
A
kh
qB
t
hAc
qB
p tp
wA
t
i
4045 .0
ln
2
1
2. 141
234 .0
2