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properties. A hydrocarbon producing reservoir — typically over two kilometres deep — will
theoretically never show porosities of O 0.4 to 0.6 bulk rock fraction. Potentially this can be
simulated in laboratory experiments. In here, cores are subjected to confined pressure comparable
to the pressure regime in a typical hydrocarbon producing reservoir. The compaction that will
occur as a result of the pressure increase can be an indication for the degree of porosity decrease in
the burial process.
3. Hardly any indication of diagenesis can be observed in the thin sections. Only a very small amount
of rim cement is present, which does not have a big influence on the pore network and hence the
potential hydrocarbons in place. A deeper burial and therefore higher pressure and temperature
will increase the speed at which cement forms. Potentially this can significantly reduce porosities,
especially in carbonates, because these sediments are associated with precipitation of dissolved
calcareous material. This effect is harder to reproduce in a laboratory, because a geological time
scale is impossible to simulate.
The permeability is the second parameter which is important for in particular the production behaviour
of a hydrocarbon producing reservoir. Because dynamic simulations are not considered in this project,
permeability has not been modelled across the reservoir grid. Table 6.1 gives — apart from the porosity —
values for the average permeability of the facies. These values are obtained with a falling head experiment
described before and with a limited number of samples.
Implications for the productive behaviour are often found in high differences in permeability. A relatively
small unit with a very high or very low permeability can influence the production significantly. Although
the differences in permeability measurements are not large, it does not exclude the possibility of the
presence of low permeability zones. For example, the cementation near fractures is significant (see figure
4.7a) which will form an obstacle for flow of reservoir fluids, even in horizontal direction.

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