Incorporation
of Detailed Fault Structure into Reservoir Models
Yielding, Graham1, Tom
Manzocchi2, Andy Heath3, Brett Freeman1, Andy
Foster1 (1) Badley Geoscience Ltd,
Relay structures and local drag are
geometric features of fault zones that are often too small to be incorporated
in reservoir models, or even mapped directly on seismic data. To examine the
sensitivity of oil production to fault-related uncertainties, we have developed
functionality in the TrapTester/TransGen software to model the effects on flow
of small-scale fault-zone structures within the full-field simulation model.
Results indicate that these fault zone characteristics can have significant
beneficial or detrimental effects on production.
For example, an unbreached relay ramp
potentially provides additional across-fault communication via tortuous flow
paths across the ramp-bounding faults and along the ramp in different layers.
Depending on the original fault compartmentalisation, such features may double
the total discounted oil production in a 30-year simulation.
We have also modelled realisations where
the mapped fault throw is varied either systematically owing to drag, or
following correlated variations owing to structural uncertainties; cases where
the fault zone is taken up by paired slip surfaces; and cases where populations
of new sub-seismic faults are introduced. Effects can be severe or subtle; for
example some cases of sub-seismic faults increase the total oil production
while reducing the discounted oil production, because the production profile
over time is radically changed by a different sweep pattern.
The transmissibility solutions, combined
with the deterministic and stochastic fault zone placement functionality, allow
representation of a range of geological fault properties. Connection
transmissibilities are calculated for the modified model and output with
respect to the parent model using appropriate ECLIPSE(™) keywords.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California