Geoscience Reference
In-Depth Information
These four questions are used in this chapter
to structure the discussion on the rock model,
followed by a summary of more specific rock
model build choices.
adopt when not representative, particularly if
modern dynamic environments are being
compared with ancient preserved systems. It is
possible to collect a library of analogue images
yet still be unclear exactly how these relate to
the reservoir in hand, and how they link to
the available well data. By contrast, the ability
to draw a conceptual sketch section is highly
informative and brings clarity to the mental
image of the reservoir held by the modeller. If
this conceptual sketch is not clear, the process
of model building is unlikely to make it any
clearer. If there is no clear up-front conceptual
model then the model output is effectively a
random draw:
2.2
Model Concept
The best hope of building robust and sensible
models is to use conceptual models to guide the
model design. We favour this in place of purely
data-driven modelling because of the issue of
under-sampling (see later). The geologist should
have a mental picture of the reservoir and use
modelling tools to convert this into a quantitative
geocellular representation. Using system defaults
or treating the package as a black box that some-
how adds value or knowledge to the model will
always result in models that make little or no
geological sense, and which usually have poor
predictive capacity.
The form of the reservoir concept is not com-
plex. It may be an image from a good outcrop
analogue or, better, a conceptual sketch, such as
those shown in Fig.
2.2
.
It should, however, be specific to the case
being modelled, and this is best achieved by
drawing a simple section through the reservoir
showing the key architectural elements - an
example of which is shown in Fig.
2.3
.
Analogue photos or satellite images are
useful and often compelling but also easy to
If you can sketch it, you can model it
An early question to address is:
“what are the
fundamental building blocks for the reservoir
concept?”
These are referred to here as the
'model elements' and discussed further below.
For the moment, the key thing to appreciate is
that:
model elements
6
¼
facies types
Selection of model elements is discussed in
Sect.
2.4
.
With the idea of a reservoir concept as an
architectural sketch constructed from model
elements established, we will look at the issues
surrounding the build of the model framework
then return to consider how to select elements to
place within that framework.
Fig. 2.2
Capturing the reservoir concept in an analogue image or a block diagram sketch
