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Geir Evensen

EnKF-ECLIPSE implementation

Geir Evensen
Bergen, Norway

New book on data assimilation available:

Geir Evensen: Data assimilation, The Ensemble Kalman Filter, Springer, 2006
Springer link and Amazon link:

Download EnKF ECLIPSE V3.2

Download EnKF ECLIPSE V3.1

Version 3.2 of the EnKF distribution,(Sep 12, 2006). Mostly minor updates related to the compilation with the linux intel compiler. The ensemble io is now given by the memlist.inc to make the states_io identical on all platforms (F90 does not have a specification of how to write a type variable as a unformatted direct file).

Version 3.1 of the EnKF distribution, specially tailored for setup with new Eclipse models, is now available (May 24, 2006). The user interface appears similar to the version 2.x but has been completely recoded in Fortran 90. Thus, the ksh scripts previously used to run all the sub-programs have been replaced with a single F90 program, and this allows for simpler debugging and a more flexible interface.

Other major changes include:

  • Automatic generation of include files representing the interface to ECLIPSE, thus no manual programming is needed when setting up a new case.
  • All the statistical priors are now specified in an xls sheet providing an interface which is rather simple to use.
  • Additional parameters such as the OWC, GOC, MULTZ, and MULTFLT are now included as variables to be estimated.
  • There are now extensive help menues included.
  • Since the previous documentation and installation menues are obselete we now refer to the enclosed README file.
  • A known bug: the Diag/summary files contains an empty line that needs to be removed. This can be done using the script fix.sh.

This page is established as a reference page for users of EnKF with the ECLIPSE reservoir simulation model. It contains a specific Fortran 90 implementation which links the EnKF to the ECLIPSE reservoir simulator and documentation on how to use it. Much of the code is the standard open EnKF code which is also available from the EnKF home page. The material on this page will provide new users of the EnKF and ECLIPSE with a quick start and spinup, and experienced users with optimized code which may increase the performence of their implementations.

The EnKF was originally proposed by Evensen (1994), and has later been further developed and examined in a large number of published papers. A recent review and overview of the EnKF is given by Evensen (2003), which provides detailed information on the formulation, interpretation and implementation of the EnKF, and now serves as a reference document for the basic methodology. A later publication Evensen (2004), provides a discussion of alternative square root schemes for the analysis step where the perturbation of measurementes is avoided. Further, it provides a discussion of ensemble sampling strategies which ensures a better conditioned ensemble, and it gives a theoretical discussion of issues related to the use of a low rank representation for the measurement error covariance matrix.

Users of the EnKF are encouraged to e-mail useful example codes and upgrades, which can be installed on this web site, to Geir Evensen.

Mail to Geir Evensen