Geoscience Reference
In-Depth Information
Static
70
60
50
40
forecast
Heterolithics
No Channels
High Connectivity
Small Bodies
Body Orientation
Low Connectivity
time of study
30
20
10
history
Dynamic
Condensate/Gas Ratio
0
0
1
2
3
4
5
6
7
8
9
Relative Permeabilities
Time (years)
Aquifer Size
Fig. 5.12
Application of deterministic scenarios to a brownfield case: forecasting production (Redrawn from Bentley
and Smith 2008, The Geological Society, London, Special Publications 309
Geological Society of London [2008])
#
matching tools - the permissible parameter
ranges for those uncertainties being established
before
the matching began.
A compiled production forecast for the 'no
further drilling case' is shown in Fig.
5.12
. The
difference between that spread of outcomes and
the spread from a parallel set of outcomes which
included water injection, was used to quantify
the value of the injection decision. Of interest
here is the nature of that spread. Although all
models gave reasonable matches to history, the
incremental difference between the forecasts was
larger than that expected by the team. It was
hoped that some of the static uncertainties
would simply be ruled out by the matching pro-
cess. Ultimately none were, despite 80 wells and
15 years of production history.
The outlier cases were reasonable model
representations of the subsurface, none of the
scenarios was strongly preferred over any other,
and all were plausible. A base case was not
chosen.
The outcome makes a strong statement about
the non-uniqueness of simulation model
matches. If a base case model had been
rationalised based on preferred guesses, any of
the seven scenarios could feasibly have been
chosen - only by chance would the eventual
median model have been selected.
The Sirikit case also confirmed that multiple
deterministic modelling was achievable in rea-
sonable study times - scaled sector models were
used to ease the handling of production data (see
Bentley and Woodhead
1998
). The workflow
yielded a surprisingly wide range of model
forecasts.
Fig.
5.13
summarises an application of sce-
nario modelling to a producing field with 4D
seismic, which generated additional insights
into the use of scenarios. The case is from the
