Characterizing locality- and scale-dependent heterogeneity in conglomerate core and associated fluid flow using X-ray CT imaging

•Local heterogeneity caused by the distribution of matrix and clasts significantly affects fluid characteristics within a few centimeter-scales.•Absolute and effective porosities varied dependent on the ratio of clast and matrix as well as the portion of isolated pores in the core sample.•Porosity-permeability relationship of the conglomerate rock was and numerically evaluated.•To analyze highly heterogeneous conglomerate rocks, the size of a core sample and the resolution of X-ray CT images need to be carefully considered.