Our study demonstrates that actual grain size does not influence porosity, but for real sandstone samples, the sorting and shape of grains affect porosity values. A range of porosity values was derived using grain parameters generated through in-house developed MATLAB codes from digital FESEM images of sandstone samples. The mixing effect on the inter-granular porosity for each unit cell packing model was analysed. Subsequently, the grain shape effects in terms of elongation degree and grain size distribution in terms of the degree of sorting were evaluated. Accordingly, this study presents static packing models for unit cells idealised for spherical and elongated grains using cubic, orthorhombic, and rhombohedral packing models. In the present study, three-dimensional packing models were generated to provide a realistic description of granular mixtures. Heterogeneities in pore space volume are present at micro- and nanoscales in granular mixtures due to packing conditions resulting from deposition and diagenesis. Granular mixtures produce complex pore space controlled by grain size, grain shape, and grain sorting. Generally, pore heterogeneity is poorly represented in subsurface geological models due to the complexity.

Porosity is the dominant factor that determines the exploitable capacity of sedimentary reservoir rocks.

River rock vs graton