SPE Journal
Volume 16,
Number 2,
June 2011,
pp. 429-439
Summary
Reservoir modeling and simulation are subject to significant uncertainty,
which usually arises from heterogeneity of the geological formation and
deficiency of measured data. Uncertainty quantification, thus, plays an
important role in reservoir simulation. In order to perform accurate
uncertainty analysis, a large number of simulations are often required.
However, it is usually prohibitive to do so because even a single simulation of
practical large-scale simulation models may be quite time consuming. Therefore,
efficient approaches for uncertainty quantification are a necessity. The
experimental-design (ED) method is applied widely in the petroleum industry for
assessing uncertainties in reservoir production and economic appraisal.
However, a key disadvantage of this approach is that it does not take into
account the full probability-density functions (PDFs) of the input random
parameters consistently--that is, the full PDFs are not used for sampling and
design but used only during post-processing, and there is an inherent
assumption that the distributions of these parameters are uniform (during
sampling), which is rarely the case in reality. In this paper, we propose an
approach to deal with arbitrary input probability distributions using the
probabilistic-collocation method (PCM). Orthogonal polynomials for arbitrary
distributions are first constructed numerically, and then PCM is used for
uncertainty propagation. As a result, PCM can be applied efficiently for any
arbitrary numerical or analytical distribution of the input parameters. It can
be shown that PCM provides optimal convergence rates for linear models, whereas
no such guarantees are provided by ED. The approach is also applicable to
discrete distributions. PCM and ED are compared on a few synthetic and
realistic reservoir models. Different types of PDFs are considered for a number
of reservoir parameters. Results indicate that, while the computational efforts
are greatly reduced compared to Monte Carlo (MC) simulation, PCM is able to
accurately quantify uncertainty of various reservoir performance parameters.
Results also reveal that PCM is more robust, more accurate, and more efficient
than ED for uncertainty analysis.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
3 December 2009
- Revised manuscript received:
1 July 2010
- Manuscript approved:
13 July 2010
- Published online:
6 January 2011
- Version of record:
17 June 2011