Re: [Sgems-users] Variogram_Kriging_ with matlab

[Thomas M. H. <tho...@gm...>]

Hi Alireza.

mGstat (http://mgstat.sourceforge.net/) contains a Matlab interface to
SGeMS that lets you call SGeMS from within Matlab and manipulate the
parameter file controlling SGeMS. If you intend to try the example
below, I suggest you download mGstat from SVN
(http://sourceforge.net/projects/mgstat/develop) as the support for
SGeMS has been updated a lot since the last release.
At the moment the semivariogram computaton of SGeMS cannot be
performed using the commandline interface, and therefore this is not
available in mGstat. You can however manually fit semivariogram models
in Matlab (see below)


Say you want to perform sequential Gaussian I suggest you try out the
small example in Chapter 3.1 in the online documentation
(http://mgstat.sourceforge.net/htmldoc/chapSGEMSuse.html#SGEMS_seqsim)

In short to to get a default SGSIM XML-parameter file loaded into matlab:
--
S = sgems_get_par('sgsim); % Loads a default SGSIM parameter file
--
All options for controlling SGeMS is in the matlab structure :
S.XML.parameters

If you want to change the variogram model, you should change the
structure below S.XML.parameters.Variogram
--
>> S.XML.parameters.Variogram
ans=
       nugget: 1.0000e-003
    structures_count: 1
         structure_1: [1x1 struct
--

To run 10 simulation with increasing range do for example:
--
for i=1:1:10
  r=i*10;
  S.XML.parameters.Variogram.structure_1.ranges.max=[r];
  S.XML.parameters.Variogram.structure_1.ranges.medium=[r];
  S.XML.parameters.Variogram.structure_1.ranges.min=[r];
  S=sgems_grid(S);
  subplot(4,3,i);imagesc(S.x,S.y,S.D(:,:,1)');
end
--

You can also specify the variogram model using a shorter notation
(same format as when using GSTAT) (only available in the SVN version):
--
     S.XML.parameters.Variogram=sgems_variogram_xml('0.1 Nug(0) + 0.4
Exp(10) + 0.5 Sph(40,30,0.2)');
--

In mGstat you will find a few m-files that should help you manully fit
a semivariogram model to the experimental semivariogram obtained from
your data. Check out 'semivar_exp_gstat.m'

I hope this can help a bit.
Have a nice day -
Thomas Mejer Hansen



2009/11/25 Alireza <ars...@ma...>:
> Dear SGEMS's friends,
>
> I am new in SGEMS and I am doing reservoir history matching in matlab. I
> like to know how I can call SGEMS from matlab to create variograms and make
> use of the created variogram to do 2D Kriging. Any comment regarding import,
> export, from/to Matlab/SGEMS and format files is appreciated.
>
> Best regards,
> Alireza,
>