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Dynamic Data Analysis – v5.12.01 - © KAPPA 1988-2017
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r 2 – T heory- p42/743
2.H.3
Effect of ‘known’ parameters
2.H.3.a
Wellbore radius
The response with all default parameters but varying the wellbore radius is illustrated below.
Values of r
w
are 0.1, 0.3, 1 and 3 ft.
The effect of a change in the wellbore radius is strictly the same as the consequence of a skin
change: Early time amplitude of the derivative hump, no middle time and late time effect on
the derivative, but a shift in the pressure that stays constant once wellbore storage effects are
over. The equivalence between wellbore radius and skin is hardly a surprise, as skin can also
be defined with respect to an equivalent wellbore radius. The well response is in fact a function
of the equivalent wellbore radius r
we
= r
w
.e
-Skin
.
Fig. 2.H.11 – Effect of wellbore radius r
w
, loglog plot
Fig. 2.H.12 – Effect of wellbore radius r
w
, semilog and history plot