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4.6 Reservoir properties

This section presents the results of the laboratory tests described in section 3.3. Table C.2 in appendix C
provides a general overview of the reservoir properties, and figure 4.13 illustrates the porosity-permeability
correlation with the results from the samples.

4.6.1 Porosity

The porosity of the Favignana calcarenite is approximately between 0.45 and 0.65, thus showing extremely
prolific values, when compared to typical hydrocarbon reservoir properties (Flu¨gel, 2010). Lowest
porosities can be found in the massive calcarenites, but even those values are rather high with a fraction
of 0.45 or higher. The most porous samples originate from the parallel laminated unit (up to 0.65), which
is striking because thin section analysis points out that these samples are relatively fine grained. Because
almost no dissolution or extensive cementation has taken place all porosity is intergranular. Because the
low degree of diagenesis, secondary types of porosity that are common in subsurface carbonate reservoirs
— like vuggy or intragranular — are not observed.

4.6.2 Permeability

All the results of the permeability laboratory experiments described in section 3.3.2 are presented table
C.2 and figure 4.13. For two samples, the resulting time versus height plots are displayed in figure
4.14a. This plot confirms the repeatability of the experiments, as the two different measurements match
reasonably.
As expected from the porosity results, also the permeability values are high — between 20 and 100 darcy
— compared to subsurface reservoir properties. Permeabilities of tens of darcy generally do not occur in
the deep subsurface. The fact that the Favignana calcarenite has not been buried several kilometres deep
can explain this highly permeable sedimentary rock.
In contradiction to the porosity results, the variation of permeability is less dependent on the origin of the
samples. Values of tens of darcy occur for most of the samples, with an exception for some cross-laminated
units. These tests resulted in abnormal values of up to 320 D, which might be caused be the bad sample
quality. Section 7.2 discusses this problem.

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