166 / 743
Dynamic Data Analysis – v5.12.01 - © KAPPA 1988-2017
Chapte
r 5 – W ellbore models- p166/743
5.B.3
Sensitivity analysis on the wellbore storage coefficient
The figure below presents the response with wellbore storage values, C of 0.001, 0.003, 0.01,
0.03 and 0.1 (stb/psi).
The value of C has a major effect, which is actually exaggerated by the logarithmic time scale.
You can see on the linear history plot that all responses seem to be the same, however.
When the influence of wellbore storage is over both the pressure change and the derivative
merge together. Wellbore storage tends to masks infinite acting radial flow on a time that is
proportional to the value of C. Wellbore storage will also tend to mask other flow regimes that
can be present in a well test. Early time well responses such as linear, bi-linear, spherical and
hemispherical flow will disappear if the storage effect is considerable. Effects of heterogeneous
reservoirs can also be masked by wellbore storage. The wellbore storage effect on other well
and reservoir models are covered in the individual chapters of these models.
Wellbore storage does not affect the late time pseudo steady state response.
Fig. 5.B.4 – Effect of wellbore storage, loglog plot
Fig. 5.B.5 – Effect of wellbore storage, semilog and history plot