3D confocal imaging methodology optimized for pore space characterization of carbonates

Pore space characterization of carbonate materials is of fundamental importance to a wide range of earth science and engineering applications. In this study, we show how confocal microscopy can be used as a reliable tool to visualize and quantify the heterogeneous pore space in carbonate materials. In confocal imagery, the quality of pore space images is controlled by various factors including the choice of fluorophore, objective lens, and me-dium of imaging. Our experiments demonstrated that there is no fit-for-all dye. The red dye provides more depth of investigation, while the blue dye can capture large pores more efficiently. Our investigation indicated that quantitative pore space description from confocal images can be significantly influenced by imaging artifacts associated with imaging the heterogeneous and complex pore space in carbonates. By applying image decon-volution, we mitigated the confocal imaging artifacts (e.g., spherical aberration, and resolution deviation), and extracted a more reliable 3D pore-network model of the carbonate sample. We employed our optimized confocal imaging protocol to visualize and quantify macro-and micropores, and more importantly their interconnectivity within an Indiana limestone (IL) sample. The computed pore-throat size distribution (PSD) from the 3D confocal images was able to capture the inherent bimodal distribution of IL.

Automated summary

In this study, confocal microscopy was used to visualize and quantify the pore space in carbonate materials. The choice of fluorophore and imaging factors influenced the quality of the pore space images. Image deconvolution was applied to mitigate imaging artifacts and obtain a reliable 3D pore-network model. The optimized confocal imaging protocol successfully visualized and quantified macro- and micropores, as well as their interconnectivity in an Indiana limestone sample.