Geoscience Reference
In-Depth Information
Static
Structure
Reservoir Properties
Sand Connectivity
'Thief' Zones
Fault Compartments
Dynamic
Relative Permeabilities
Aquifer Behaviour
WellProductivity (Hydraulic Fractures,
Condensate Drop-out, WellType)
Fluid Composition
-
changes
+
Fig. 5.11 Application of deterministic scenarios to a green field case: forecasting costs (Redrawn from Bentley and
Smith 2008, The Geological Society, London, Special Publications 309 # Geological Society of London [2008])
The above example was conducted without
selecting a 'base case' model. A development
scheme was ultimately selected, but this was
based on a range of outcomes defined by the
subsurface team.
Scenario modelling for greenfields has been
conducted many times since the publication of
this example. In the experience of the authors,
the early learnings described in the case above
have held true, notably:
• Large numbers of scenarios are not required to
capture the range of uncertainty;
• The main uncertainties can generally be
drawn up through cross-discipline discussion
prior to modelling - if not these can be
established by running quick sensitivities;
• This list should be checked and iterated as the
modelling progresses;
• The dominant uncertainties on a development
project do not always include the issue of
seismically driven gross rock volume, even
at the pre-development phase;
5.6.2 Brownfield Case
Two published examples are summarised here
which illustrate the extension of scenario
modelling to mature, or 'brownfield', reservoir
cases.
The first concerns the case of the Sirikit Field
in Thailand (Bentley and Woodhead 1998 ). The
requirement was to review the field mid-life and
evaluate the potential benefit of introducing
water injection to the field. At that point the
field had been on production for 15 years, with
80 wells producing from a stacked interval of
partially-connected sands. The required outcome
was a quantification of the economic benefit of
water injection, to which a scenario-based
approach was to be applied.
The uncertainty list is summarised in
Fig. 5.12 . The static uncertainties were used to
generate the suite of static reservoir models for
input to simulation. In contrast to the greenfield
cases, where production data is limited, the
dynamic uncertainties were used as the history
It is not necessary to select a base case model.
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