SISIM categorial (problem with assign hard data to simulation grid) More facies than expected


JeanB - Posted on 23 June 2011

Dear all

  • here is the issue: more facies than expected when using 'assign hard data to simulation grid' within categorial SISIM.
  • What I would like to do : a Sequential Indicator Simulation of geological facies (categorial) conditionned upon synthetic data. I got a realization of 3 facies instead of 2 as expected (one more than expected in each case). One facies limited to data point of facies x.

    First I simulated two random facies in Matlab (50 data points) in a grid 100 x 100, unit spacing. Then I run SISIM conditionned upon my hard data in SGeMS to get one realization with 2 facies. In property item (Hard data parameters) I selected facies data, not indicators (am I right?). In interval data, I selected nothing. The problem comes when I select 'assign hard data to simulation grid' item. I get a realization with 3 facies instead of 2,i.e. one facies = 0, another one = 1 and the last one = 2. The latter is restricted to the data point of facies 2. The same problem also happens if I select my two indicators in interval data and my facies in property. However, if I select one indicator in property instead of facies, I get two facies as expected, but conditionning occurs on one indicator only.

    • Same problem in two examples:
        "S-GeMS Tutorial Notes" , 26 june 2007, Geoff Bohling from Kansas Geological Survey. Here, the author simulates 5 facies, but I can see 6 facies in the realization (data and parameters are provided at http://people.ku.edu/~gbohling/BoiseGeostat/TutorialData.zip. Pdf : http://people.ku.edu/~gbohling/BoiseGeostat/SGeMSTutorial.pdf.
          Also, in "Geostatistical Earth Modeling Software: User’s Manual" , Nicolas Remy , 2004 : the example illustrated at Figure 3.8 using Stanford V data set and the same parameters. Again, result seems similar but if we zoom on it (in SGeMS), there are more facies than expected. Here also, assign hard data to simulation grid is predifined in Bohling's parameters file, and just not mentioned in Remy's one.

            My question : do I have to omit 'assign hard data to simultion grid'? And so, how to keep hard data on the realization?

          Any help would be appreciated

          Thanks in advance

  • ..
    Could you please send me some data (in gslib format) with your parameter file on which this problems occurred. This is very strange. I am currently on vacation and will look at it at my return on the second week of July.

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