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Re: GEOSTATS: Sampling.Grid

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  • Med Bennett
    ... What are you sampling for and attempting to interpolate? Are you trying to interpolate along section (1D), across the outcrop (2D), or in three dimensions?
    Message 1 of 3 , Jun 9, 1997
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      At 12:32 PM 6/4/97 -0700, you wrote:
      >Hello . . .
      >
      >I am a Hydrogeology Master's student with a sampling grid question.
      >
      >I will be sampling a number of vertically exposed sedimentary beds which
      >vary in thickness between 10 and 160 cm. Geostats will be performed on
      >each of these beds individually as well as for the complete data set.
      >I realize that I need a regularly spaced sampling interval with 30-40
      >samples per bed. The necessary grid will need to be very fine for the
      >thin beds. If I apply this same grid to the thick beds, my sample
      >population will be extremely high and will necessitate an overload
      >of analyses.
      >
      >Would it be statistically correct to generate a sampling design which
      >includes 30-40 samples per bed with sample spacing that is *proportional*
      >to the bed thickness? If not could you give me some other suggestions?
      >
      >Thank you very much for your time.
      >
      >Michael Pickering
      >Washington State University
      >six41@...
      >
      What are you sampling for and attempting to interpolate? Are you trying to
      interpolate along section (1D), across the outcrop (2D), or in three
      dimensions? Geostats may be overkill or inappropriate if you are trying to
      quantify changes vertically through the section (depth or time).
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    • Syed.R.Syed@EXXON.sprint.com
      Michael Pickering s questions refer (i.e. using sampling interval proportional to bed thickness): 1. It s good to be familiar with: (a) what the end result
      Message 2 of 3 , Jun 10, 1997
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        Michael Pickering's questions refer (i.e. using sampling interval
        proportional to bed thickness):

        1. It's good to be familiar with: (a) what the end result will be used
        for; and, (b) what scales of heterogeneity will most impact that
        end result. E.g. in a petroleum deposit, lamina scale heterogeneity
        may or may not impact a fluid flow process, therefore sampling must
        take into account this knowledge, regardless bed thickness.

        2. It's even conceivable that a smaller bed might not show as much
        heterogeneity as a thicker bed, i.e. due to erosion of part of the
        smaller bed. That thicker bed might show varying scales of
        heterogeneity which the sampling should try to capture as much as
        possible. Some intuitive decisions need to be made.

        3. Re: (1) and (2) above, I suggest that the sampling scheme be based
        on some sound subjective (geological) understanding of the phenomena,
        and a knowledge of the impact of the eventual description on whatever
        transfer function will be applied (whether fluid flow simulation or
        otherwise). The problem isn't as tractable as it "seems" no matter
        how statistical you want to make it.

        Regards, Syed

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