SPE Journal
Volume 16,
Number 2,
June 2011,
pp. 294-306
Summary
The ensemble Kalman filter (EnKF) has been used widely for data
assimilation. Because the EnKF is a Monte Carlo-based method, a large ensemble
size is required to reduce the sampling errors. In this study, a probabilistic
collocation-based Kalman filter (PCKF) is developed to adjust the reservoir
parameters to honor the production data. It combines the advantages of the EnKF
for dynamic data assimilation and the polynomial chaos expansion (PCE) for
efficient uncertainty quantification. In this approach, all the system
parameters and states and the production data are approximated by the PCE. The
PCE coefficients are solved with the probabilistic collocation method (PCM).
Collocation realizations are constructed by choosing collocation point sets in
the random space. The simulation for each collocation realization is solved
forward in time independently by means of an existing deterministic solver, as
in the EnKF method. In the analysis step, the needed covariance is approximated
by the PCE coefficients. In this study, a square-root filter is employed to
update the PCE coefficients. After the analysis, new collocation realizations
are constructed. With the parameter collocation realizations as the inputs and
the state collocation realizations as initial conditions, respectively, the
simulations are forwarded to the next analysis step. Synthetic 2D water/oil
examples are used to demonstrate the applicability of the PCKF in history
matching. The results are compared with those from the EnKF on the basis of the
same analysis. It is shown that the estimations provided by the PCKF are
comparable to those obtained from the EnKF. The biggest improvement of the PCKF
comes from the leading PCE approximation, with which the computational burden
of the PCKF can be greatly reduced by means of a smaller number of simulation
runs, and the PCKF outperforms the EnKF for a similar computational effort.
When the correlation ratio is much smaller, the PCKF still provides estimations
with a better accuracy for a small computational effort.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
17 January 2010
- Revised manuscript received:
9 May 2010
- Manuscript approved:
13 July 2010
- Published online:
6 January 2011
- Version of record:
17 June 2011