Geoscience Reference
In-Depth Information
Fig. 2.43
The Franken
Field.
Top image
: the two
zone subdivision;
middle
image
: object model (no
trends applied, stationarity
maintained);
bottom image
:
trended object model
number of the models were made quickly using
system defaults and have little substance;
stationarity (within zones) is dominant and
although the models are statistically valid, they
lack an underlying concept and have poor deter-
ministic control. Only the lower models in each
Figure take account of the trends associated
with the underlying reservoir concept, and it is
these which are the superior representations - at
least matching the quality of the conceptual
interpretation.
The main point to take away from this example
is that all the models match the well data and no
mechanical modelling errors have been made in
their construction, yet the models differ drasti-
cally. The comparison reinforces the importance
of the underlying reservoir concept as the tool for
assessing which of the resulting rock models are
acceptable representations of the reservoir.
2.8
Summary
In this chapter we have offered an overview of
approaches to rock modelling and reviewed a
range of geostatistically-based methods, whilst
holding the balance between probability and
determinism and the primacy of the underlying
concept as the core issues. Reservoir modelling
is not simply a process of applying numerical
tools to the available dataset - there is always an
element of subjective design involved. Overall the
rock model must make geological sense and to
