Exploration of the “Nugget Effect”

Abstract

Many people believe the “Nugget Effect” is the result of rap: in-situ changes in the concentration of a given constituent interest, taking place on a very small scale. They are right however, there is much more to it. Indeed, the “Nugget Effect is the result of at least seven types of variability:

• 1 The true in-situ, small-scale, random variability;

• 2 The variability introduced by Constitution Heterogenei during all sampling and subsampling stages, which is function of fragment size and sample or subsample weight

• 3 The variability introduced by small-scale Distributiol Heterogeneity during all sampling and subsampling stages which is a function of transient segregation as soon a the material has been broken up;

• 4 The variability introduced by any deviation from an isotropic module of observation ensuring sampling equiprobability in all relevant dimensions, during al: sampling and subsampling stages;

• 5 The variability introduced by selectivity and poor recovery during all sampling and subsampling stages;

• 6 The variability introduced by contamination, losses, alteration of physical or chemical properties, and huma errors; and

• 7 The variability introduced by the analytical procedure

The misunderstanding of all these variability component prevents the effective minimization of the errors the generate. Accordingly, discrepancies between exploratic estimates and production realities are likely to occur. Th: paper intends to be pragmatic in order to set a logica strategy that minimizes the “Nugget Effect”, allowing go Geostatistics to proceed smoothly and sucessfully: Failure do so can lead to errors which are very difficult to correct with statistics.