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Re: AI-GEOSTATS: Automated Variogram modelling

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  • Syed Abdul Rahman Shibli
    Just to echo Pierre and Ed s remarks, I think it is easy to be trapped in analysis paralysis when it comes to variogram modelling. It s also easy to lose
    Message 1 of 7 , Apr 5, 2004
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      Just to echo Pierre and Ed's remarks, I think it is easy to be trapped in "analysis paralysis" when it comes to variogram modelling. It's also easy to lose sight of the goals of the interpolation process, and also the inherent limitations of working with experimental variograms. In some problem domains, interpolation results transcend the static and move into the dynamic realm via a transfer function such as a reservoir simulator.

      I've seen some geoscientists (in petroleum) spending an inordinate amount of time fine tuning horizontal variogram models based on five or six appraisal wells and very few pairs at each lag distance. My usual response to such cases is to suggest to the person to come up with a (qualitative) variogram model that made sense to them as geoscientists instead of basing it on well information.

      Some studies spend months coming up with a detailed matrix permeability model in a fractured carbonate reservoir when most well test data point to super K production and is not matrix dominated. This does not help much when one is trying to determine such parameters as injection recovery efficiency. It might only help in getting a first pass volumetric estimate, but unfortunately (or fortuantely) shareholders are normally interested in reserves and not what is in place.

      Just my two cents worth.

      Cheers,

      Syed

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    • sanguinetti.henri
      Pierre and Isobel comments are very interesting. In the particular cases of mining companies, they are even more relevant. Effectively we get many data in
      Message 2 of 7 , Apr 6, 2004
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        Pierre and Isobel comments are very interesting.
        In the particular cases of mining companies, they are even more relevant.
        Effectively we get many data in mining, but we have to remember that the
        experimental variograms are dependant of the sampling pattern, ie drilling
        grid, drilling orientation, sampling along drill hole ..etc..
        Consequently each direction of calculation should be "weighed" carefully and
        using what is known about the geology.
        Of course it's long and cumbersome. But if you hate cooking bread you should
        not be a baker.
        "the proof in the pudding"..yes, be careful that the mining companies are
        not as well.

        Henri



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