The microstructure and evolution of pore space in rocks is a critically important factor controlling fluid flow. The size, distribution and connectivity of these confined geometries dictate how fluids, including H2
O and CO2
, migrate into and through these micro- and nanoenvironments, wet and react with the solid. (Ultra)small-angle neutron scattering and autocorrelations derived from BSE imaging provide a method of quantifying pore structures in a statistically significant manner from the nanometer to the centimeter scale. Multifractal analysis provides additional constraints. Analyses of experimental and natural samples of St. Peter sandstone show total porosity correlates with changes in pores structure including pore size ratios, surface fractal dimensions, and lacunarity. This information can also be used to constrain computer-generated, random, three-dimensional porous structures. The results integrate various sources of experimental information and are statistically compatible with the real rock. This allows a more detailed multi-scale analysis of structural correlations in the material.