Page 69 - MSc_thesis_R A Kil

Table 6.1 – Average petrophysical properties of the facies in the model, including the sample
sources. Numbers according to table 3.1.

Facies φavg. [-] kavg. [D] Source

Massive calcarenite 0.46 52 2

Parallel laminated units 0.63 66 1

Undulated lamination 0.63 66 1

Tabular cross-stratification 0.57 65 3

Large dune foresets 0.57 65 3

Small scale trough cross-stratification 0.58 65 3,4

Homogeneous scour fills 0.46 52 2

6.2 Property modelling

Results from the laboratory tests on the samples, are modelled into the reservoir model grid. Each
grid cell has at this stage only an assigned facies code. In addition two additional properties can be
given to all the cells: porosity and permeability. The most convenient approach is to establish a specific
property distribution for each facies. In practice results from wireline logging result in for example a
porosity log with values every couple of centimetres. The data from the field has a much lower resolution.
Moreover, not every facies as they appear in current subdivision is sampled. Therefore some assumptions
have to be made. In table 6.1 an overview of these assumptions and the reservoir properties used in
the modelling process is given. Because of the lack of samples, the large dune foresets properties are
assumed to be equal those of the tabular cross-stratified beds. Erroneous results from permeability tests
on trough cross-stratified samples resulted in the same permeability for all cross-stratified units. Both the
homogeneous deposits on the bottom of the sequence and the scour fills share the same average properties.
The last assumption is the fact that the undulated lamination is equal in porosity and permeability to
the parallel laminated units, as they are both relatively fine grained. The final porosity model of eastern
Favignana is presented in figure D.6 in appendix D. A permeability model was not created because no
dynamic simulations are part of this study.

6.3 Reservoir implications

As indicated earlier, the Favignana calcarenite has a very prolific reservoir quality. This is caused by
several reasons: 1) a high porosity; 2) high permeability; 3) very few faults and fractures; and 4) a low
degree of diagenesis. The main explanation of these excellent reservoir properties is that on eastern
Favignana almost no compaction has taken place. If these deposits were buried, all these parameters would
have changed significantly. The compaction causes a reduction in porosity and therefore permeability,
fractures can develop due to differential load, and more cementation can form over time. However, the

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