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Dynamic Data Analysis – v5.12.01 - © KAPPA 1988-2017
Chapte
r 2 – T heory- p39/743
2.H.2.b
Skin
Below is shown the response with all default parameters and a variable skin. Values for skin
are -3, 0, 2, 5 and 10.
Storage: Skin does not change the position of the early time unit slope (pure wellbore storage)
but affects the amplitude of the hump. A larger skin will produce a larger hump, hence
delaying the time at which Infinite Acting Radial Flow is reached.
IARF: Once IARF is reached, the skin has no effect on the vertical position of the derivative,
but has a cumulative effect on the amplitude of the pressure.
PSS: Skin does not have an effect on the time at which PSS is reached or on the derivative
response at the end. However the cumulative effect on the pressure remains and all responses
‘bend’ and remain parallel when PSS is reached (see history plot below).
Fig. 2.H.5 – Effect of skin, loglog plot
Fig. 2.H.6 – Effect of skin, semilog and history plot