Electron Microscopy of Core Samples
Phenom SEM BSD image of Berea sandstone in pore-filling clay region of interest
The porosity and composition of sedimentary rocks like sandstone and siltstone may be characterized using scanning electron microscopy (SEM) as a complementary technique to other established methods for the oil and gas industry. Berea sandstone is commonly used as a standard core sample. Regions with grains, pores and pore-filling clays are observed in these backscattered electron detector (BSD) images showing material contrast. For elemental composition (not shown), EDS at a point, across a line or as a map contribute additional information to correlate material phase and structure.
Optical image (a) is used to select a location for SEM imaging. SEM image at 490x magnification (b) indicates locations selected for higher magnification images. SEM BSD image (c) at 8300x is from the granular area (location 1). A pore-filling clay (location 2) region is shown with an SEM image (d) magnification of 7900x.
A siltstone core sample is shown for comparison. Siltstone has smaller pore sizes. The morphology of siltstone is distinct from the Berea sandstone as shown in the SEM images at 1000x and 20000x.
SEM BSD images of siltstone sample at 1000x and 20000x, left and right respectively