Abstract of the paper ``Using two-point correlation functions to characterize microgeometry and estimate permeabilities of sandstones and porous glass'' with S. C. Blair and P. A. Berge

We have developed an image processing method for characterizing the microstructure of rock and other porous materials, and to provide a quantitative means for understanding the dependence of physical properties on the pore structure. This method is based upon the statistical properties of the microgeometry as observed in scanning electron micrograph (SEM) images of cross-sections of porous materials. The method utilizes a simple statistical measure of microstructure called the spatial correlation function, which can be used to predict bounds on permeability and other physical properties. Using SEM images, we obtain estimates of the porosity and specific surface area of the material from the two-point correlation function. The specific surface area can be related to the permeability of porous materials using a Kozeny-Carman relation. We show that image resolution determines the specific surface area (s) measured on an image and that for the sandstones studied here, the appropriate choices of image magnificiation can be made so the measured s is consistent with the specific surface area used in a simple flow model for computation of permeability. In this paper, we discuss the two-point spatial correlation function and its use in characterizing microstructral features such as pore and grain sizes. We present estimates of permeabilities found using SEM images of several different porous glasses and natural sandstones. Comparison of the estimates to laboratory measurements shows good qualitative agreement and quantitative agreement within about a factor of 2.

To obtain a copy of this paper, please contact Steve Blair: E-mail to blair@s55.es.llnl.gov