Sebastiano
Your standardisation produces a mean of zero and a standard deviation of 1, without changing the characteristics of the semi-variogram (range, relative nugget effect etc.)
I presume you will standardise each 'layer' separately? Then use a 3D search which does not include samples from layers above and below the current one. Sounds very neat and efficient if your layers are flat and horizontal.
Yes, I would definitely try that and see what you get. Let us know!
All the best
Isobel
