Microporous carbonates host a significant portion of the remaining oil-in-place in the giant carbonate reservoirs of the Middle East. Carbonates host wide range of pore sizes, however the key element influencing hydrocarbon flow is pore interconnectivity. We evaluate the use of confocal microscopy to image fluorescent epoxy pore casts of microporous carbonates. The acquired high-resolution 3D confocal images are used to gain invaluable insights on the interconnectivity between macroporosity and microporosity. We analyzed the sensitivity of quality of epoxy pore cast images to: fluorochrome selection, objective lens, and imaging medium by imaging standard fluorescent spherical beads. Guided by the sensitivity results, we acquired 3D images of the multi-modal pore space in an Indiana limestone sample with lateral- and axial-resolution of 0.36 µm and 2 µm, respectively. And we were able to identify the multi-scale pore types in the studied carbonate sample and highlight their interconnectivity.

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