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In-Depth Information
Fig. 2.9
Sequence stratigraphic elements
predominant model elements. These may be
parasequences organised within a larger-scale
sequence-based stratigraphic framework which
defines
2.4.3.6 Exotic Elements
The list of potential model elements is as diverse
as the many different types of reservoir, hence
other 'exotic' reservoir types must be mentioned,
having their own model elements specific to their
geological make-up. Reservoirs in volcanic rocks
are a good example (Fig.
2.12
), in which the key
model elements may be zones of differential
cooling and hence differential fracture density.
***
The important point about using the term
'model element' is to stimulate broad thinking
about the model concept, a thought process which
runs across the reservoir geological sub-disciplines
(stratigraphy, sedimentology, structural geology,
even volcanology). For avoidance of doubt, the
main difference between the model framework
and the model elements is that 2D features are
used to define the model framework (faults, uncon-
formities, sequence boundaries, simple bounding
surfaces) whereas it is 3D model elements which
fill the volumes within that framework.
Having defined the framework and identified the
elements, the next question is howmuch information
to carry explicitly into the modelling process. Every-
the main reservoir
architecture
(e.g.
Fig.
2.9
).
2.4.3.4 Diagenetic Elements
Diagenetic elements commonly overprint
lithofacies types, may cross major stratigraphic
boundaries and are often the predominant feature
of carbonate reservoir models. Typical diage-
netic elements could be zones of meteoric
flushing, dolomitisation or de-dolomitisation
(Fig.
2.10
).
2.4.3.5 Structural Elements
Assuming a definition of model elements as
three-dimensional features, structural model
elements emerge when the properties of a vol-
ume are dominated by structural rather than
sedimentological or stratigraphic aspects. Fault
damage zones are important volumetric struc-
tural elements (e.g. Fig.
2.11
) as are mechanical
layers (strata-bound fracture sets) with properties
