Microgeometry I: Autocorrelation and rock microstructure

The microscopic texture of a sedimentary rock vitally affects its mechanical, electrical, and fluid dynamic properties. Use of the autocorrelation function, or its Fourier dual the power spectral density function, has been suggested for texture description (Davis and Preston, 1972; Haralick, 1979; Matheron, 1967).A discussion is presented herein of the theoretical appropriateness of the autocorrelation function for rock physics texture modeling. Autocorrelograms are examined for digitized images of Berea sandstone, Whitestone limestone, a composite of glass beads, and various test patterns. Porosity and anisotropy are determined from the autocorrelograms, and noise effects seem negligible. Details about packing or distributions of sizes and shapes in granular mixtures are obtainable from the autocorrelograms.