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7 Discussion

7.1 Sedimentation deformation structures

The assumed high sedimentation rate associated with the extensive massive deposits and the large foresets
may be supported by several features observed in the field, that are not yet discussed. Some locations show
sedimentary structures formed after deposition (figure 7.1). They are interpreted as post-sedimentary
structures and perturbations which could be caused by several mechanisms. Water escape structures,
formed when water between the grains of the sediment suddenly escapes due to the increased load and
pressure are associated with a high sedimentation rate, which does not allow the water to gradually escape.
Similarly this can be generated by sediment shaking — due to earthquakes, which are still common in
the area — or by fast movement of pore water induced by gravity processes.

7.2 Reservoir properties

The porosity and permeability measurements obtained using the test described in respectively section
3.3.1 and 3.3.2 are considered to be reliable. Measurement did not differ much between different runs,
and samples with the same origin appeared to have more or less the same properties (see section 4.6). A
high variability of results from the different samples derived from the same type of sediment facies would
either suggest that the measurement method is not reliable, or that the heterogeneity of the deposits is
very high. The small diameter plugs could not be tested with the picnometer. No reliable result could be
obtained because the gas chamber that houses the sample was too large compared to the dimensions of
those plugs. The same holds for the permeability tests, where no small enough seal was available.
Porosity determination from thin sections was not possible because the blue dye did not penetrate the
samples perfectly, making it impossible for an image detection program to separate pores from grains.
Secondly, some mechanically induced disturbance of rock fabric appears to have taken place during the
thin section preparation procedure. Grains must have undergone a change in position or orientation
which did not allow any reliable porosity measurement.

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