## 4 Conclusions  
In this study, we developed a protocol to evaluate the parameters of the resin impregnation procedure used to fabricate pore casts of porous materials. We used silicon micromodels as testing specimens to optimize the impregnation pressure, time, and resin viscosity, producing high-quality pore casts. Then, we used the optimized pore casting fabrication procedure to capture the complex pore space of micritic carbonates. Carbonate pore casting was accompanied by rock matrix etching for the casts to be suitable for high-resolution 3D confocal imaging. Figure 16: Confocal images of the etched epoxy pore cast of Indiana limestone, where the solid represents the pore space and the etched away grains are white. Sample (**A**) was imaged with the 10\(\times\) air objective and the resolution of 1.6 \(\upmu\)m per pixel for the total size of 2.3 mm \(\times\) 2.3 mm \(\times\) 0.33 mm. Sample (**B**) was imaged with the 20\(\times\) water immersion objective and the resolution of 0.34 \(\upmu\)m per pixel for the total size of 0.7 mm \(\times\) 0.7 mm \(\times\) 0.9 mm. The higher resolution CLSM images allowed detecting types of microporosity: the micritic intragranular microporosity (IGM) can be seen within the grains. The micrite cement (MC) can be seen along the rims of allochems. The inter-particle (IP) pores are the relatively large voids at the junctions of the allochems. From our silicon micromodel experiments, we identified a number of defects and artifacts that arose during the resin pore casting. Most of these defects can be attributed to resin shrinkage, which we think is generally underreported. In our work, we identified two types of shrinkage defects: voids formed within the resin and cracks developed across the resin structure. The shrinkage defects were found to be more aggressive when degassing was performed under higher vacuum levels or for a longer time. We also noted that diluting resin with solvents, such as toluene, to reduce the resin viscosity caused aggressive defects and deteriorated the optical and mechanical properties of the cured resin. Pore cast etching is a critical prerequisite to capturing the high-quality 3D images of carbonates pore space. Thus, micro-CT scans validated our etching procedure by evaluating the porosity values of the pre- and post-etching sample. The micro-CT images also showed that some minor defects still persisted, but these defects represented only 0.21% of the sample's pore volume. In summary, the main outcome of this paper is a robust experimental procedure for obtaining high-quality epoxy pore casts of complex porous materials. We applied this procedure to characterize the pore space of micritic carbonates with confocal imaging. Conceptualization, T.P., M.Y. and A.H.; methodology, M.Y. and A.H.; software, A.H.; validation, A.H., V.C. and M.Y. ; formal analysis, A.H. and M.Y. ; investigation, A.H., M.Y. and V.C. ; resources, T.P. ; data curation, T.P. ; writing--original draft preparation, A.H.; rewriting manuscript--review and editing, T.P., M.Y. and V.C. ; visualization, A.H.; supervision, T.P., M.Y. and V.C. ; project administration, T.P. ; funding acquisition, T.P. All authors have read and agreed to the published version of the manuscript. [PERSON] (Ph.D. student) and [PERSON] (Research Scientist) are supported by baseline research funding from KAUST to [PERSON]. [PERSON] is supported by Ali I. Al-Naimi Petroleum Engineering Research Center (ANPERC) at KAUST. Not applicable. We thank [PERSON] from Tescan-XRE for acquiring the micro-CT images. We are grateful to the Nanofabrication Core Lab team at KAUST, especially to [PERSON] and [PERSON], for their support in fabricating the silicon micromodels. KAUST has funded this project through the Ali I. Al-Naimi Petroleum Engineering Research Center (ANPERC). The authors declare no conflict of interest. The following abbreviations are used in this manuscript: