Geoscience Reference
In-Depth Information
Fig. 4.28
Illustration of
the transfer of a structural
geological model to a
reservoir simulation grid
(Redrawn from Ringrose
et al.
2008
, The Geological
Society, London, Special
Publications 309
#
Geological Society of
London [2008])
2005
) and flow simulation on faulted grids
remains a challenge.
significant. This is a clear argument in favour
of explicit multi-scale reservoir modelling.
Furthermore, in the studies where the effects
of structural heterogeneity were assessed, both
structural and sedimentary features were found to
be significant. That is to say, structural features
and uncertainties cannot be neglected and are
fully coupled with stratigraphic factors.
Another approach to this question is to con-
sider how the fluid forces will interact with the
heterogeneity in terms of the REV (Fig.
4.29
).
Pore and lamina-scale variations have the stron-
gest effect on capillary-dominated fluid pro-
cesses while the sequence stratigraphic (or
facies association) scale most affects flow pro-
cesses in the viscous-dominated regime. Gravity
operates at all scales, but gravity-fluid effects are
most important at the larger scales, where signif-
icant fluid segregation occurs. That is, when both
capillary forces and applied pressure gradients
fail to compete effectively against gravity
stabilisation of the fluids involved.
Several projects have demonstrated the eco-
nomic value of multi-scale modelling in the
4.3.6 Which Heterogeneities Matter?
There are a number of published studies in
which the importance of different multi-scale
geological factors on reservoir performance
have been assessed. Table
4.3
summarizes the
findings of a selection of such studies in which a
formalised experimental design with statistical
analysis of significance has been employed. The
table shows only the main factors identified in
these studies (for full details refer to sources).
What is clear from this work is that several
scales of heterogeneity are important for each
reservoir type. While one can conclude that
stratigraphic sequence position is the most
important factor in a shallow marine deposi-
tional setting or that vertical permeability is
the most important factors in tidal deltaic
setting, each case study shows that both larger
and
smaller-scale
factors
are
generally
