  A quantitative comparison of the pore space geometry for three natural
sandstones is presented. The comparison is based on local porosity theory which
provides a geometric characterization of stochastic microstructures. The
characterization focusses on porosity and connectivity fluctuations. Porosity
fluctuations are measured using local porosity distributions while connectivity
fluctuations are measured using local percolation probabilities. We report the
first measurement of local percolation probability functions for experimentally
obtained threedimensional pore space reconstructions. Our results suggest to
use local porosity distributions and percolation probabilities as a
quantitative method to compare microstructures between models and experiment.
