Use of digital image analysis to estimate fluid permeability of porous materials: Application of two-point correlation functions

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Abstract
Scanning electron microscope images of cross sections of several porous specimens have been digitized and analyzed using image processing techniques. The porosity and specific surface area may be estimated directly from measured two‐point spatial correlation functions. The measured values of porosity and image specific surface were combined with known values of electrical formation factors to estimate fluid permeability using one version of the Kozeny‐Carman empirical relation. For glass bead samples with measured permeability values in the range of a few darcies, our estimates agree well (±10–20%) with the measurements. For samples of Ironton‐Galesville sandstone with a permeability in the range of hundreds of millidarcies, our best results agree with the laboratory measurements again within about 20%. For Berea sandstone with still lower permeability (tens of millidarcies), our predictions from the images agree within 10–30%. Best results for the sandstones were obtained by using the porosities obtained at magnifications of about 100× (since less resolution and better statistics are required) and the image specific surface obtained at magnifications of about 500× (since greater resolution is required).