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On the undesired effects at construction of trends in the empirical dependences

Authors: R.A. Rezvanov (Oil and Gas Research Institute of RAS, PANGEYA ZAO, RF, Moscow)

Key words: empirical dependence, trend, permeability, Exell.

Tests on artificial arrays and real petrophysical data shown that the program Exell at the construction of a number of non-linear trends averages the values not the quantities Y themselves, but some of their functions (usually f -1 (Y)). Calculations based on these trends may produce biased estimates of the expectation Y for each X. For example, the trend of exponential dependence of permeability on porosity, constructed in the program Exell, averages not permeability at a given value of porosity, but values of the permeability logarithm. Ways to exclude such deviations are proposed and tested.

References

1. Dieva E.V., Dyad'kin I.G., Ruchkin A.V., Neftegazovaya geologiya i geofizika, 1978, no. 5.

2. Ingerman V.G., Rezvanov R.A., Obzornaya informatsyya. Razvedochnaya geofizika, 1974, V. 63.

Key words: empirical dependence, trend, permeability, Exell.

Tests on artificial arrays and real petrophysical data shown that the program Exell at the construction of a number of non-linear trends averages the values not the quantities Y themselves, but some of their functions (usually f -1 (Y)). Calculations based on these trends may produce biased estimates of the expectation Y for each X. For example, the trend of exponential dependence of permeability on porosity, constructed in the program Exell, averages not permeability at a given value of porosity, but values of the permeability logarithm. Ways to exclude such deviations are proposed and tested.

References

1. Dieva E.V., Dyad'kin I.G., Ruchkin A.V., Neftegazovaya geologiya i geofizika, 1978, no. 5.

2. Ingerman V.G., Rezvanov R.A., Obzornaya informatsyya. Razvedochnaya geofizika, 1974, V. 63.


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