43 / 743
Dynamic Data Analysis – v5.12.01 - © KAPPA 1988-2017
Chapte
r 2 – T heory- p43/743
2.H.3.b
Porosity
The figure below presents the response with all default parameters but varying the porosity.
Values for
are 3%, 10% and 30%.
Storage and IARF: Porosity behaves like the skin or the well radius. A smaller porosity
produces a higher hump on the derivative but does not change the derivative IARF level. The
equivalence between porosity and skin is used in two different areas. In interference tests the
skin has a marginal influence, and the pressure amplitude is used to assess the porosity.
Hydrogeology: Hydrogeology will assess a value of skin (generally zero) and use the absolute
value of the pressure change to assess the Storativity S, i.e. the porosity.
For a given reservoir size, the time for PSS is proportional to
. Underestimating the porosity
by 10% will provide an overestimation of the reservoir bulk volume of 10%, and therefore an
overestimation of the boundary distance. The total pore volume will remain correct.
Fig. 2.H.13 – Effect of the reservoir porosity, loglog plot
Fig. 2.H.14 – Effect of the reservoir porosity, semilog and history plot