Image Acquisition

Fontainebleau sandstone is an ideal experimental system for this study. First, experimental data is available for the elastic properties of Fontainebleau sandstone over a range of porosity [Han 1986]. Second, Fontainebleau is homogeneous, made up of a single mineral, quartz, does not contain clay, and the structure of the sandstone is quite simple as it only displays intergranular porosity. Modeling the system as a simple two-phase material may be expected to provide a good match to experimental data. The images were obtained from 4.52-mm diameter cylindrical core samples extracted from each of 4 blocks of Fontainebleau sandstone with bulk porosities $\phi=7.5\%$ = 7.5%, 13%, 15%, and 22%. A 2.91-mm length section of each core was imaged [Flannery 1987, Dunsmuir 1991, Spanne 1994]. The reconstructed images have a resolution of 5.7 µm resulting in 795 x 795 x 512 imaged sections. X-ray computed tomographic images of porous media are grey scale images, usually with a bimodal population apparent, one mode corresponding to the signal from the void space, the second to the signal from the grain space. Each grey scale image was thresholded using a kriging-based thresholding method [Oh and Lindquist 1999] to give a binary pore-solid image [Lindquist and Venkatarangan1999, Lindquist 2000]. From the original cylindrical plug, we extracted the central 480³ cubic subset for analysis, corresponding to a volume of 20.5 mm³.