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Holographic 3‐D laser imaging into sandstone

With a novel imaging technique that uses holographic recording and reconstruction to perform laser‐ranging into translucent media, we have imaged several grain layers into a sandstone sample. Three‐dimensional microscale (10 micron lateral and 30 micron depth resolution) information on grain size and geometry was obtained as deep as 400 microns into the sample without thin‐sectioning. Surficial grain features in the holographic reconstruction were associated with features observed using conventional optical and scanning electron microscopy. This imaging technique represents a new form of nondestructive evaluation of grain and pore structure in reservoir rock by acquiring full‐field images at variable depths, unlike sequential scanning microscopy that requires tomographic reconstruction.