From Geometric Similarity to Behavioral Equivalence: 3D-Printed Synthetic Cores and Microfluidic Core Chips

Natural-core flooding remains a benchmark for characterizing reservoir properties and multiphase transport. Its mechanistic value is nevertheless constrained by sample scarcity, opacity, heterogeneity, and limited repeatability. Three-dimensional (3D) printing and microfluidic fabrication provide complementary routes from digital pore models to controlled physical experiments. This critical review compares 3D-printed synthetic cores with microfluidic core chips across fabrication methods, material systems, surface functionalization, fluid–rock interactions, multiphase-flow visualization, and emerging geoenergy applications. We organize their validation through four progressive levels: geometric, petrophysical, interfacial, and behavioral equivalence. Available studies demonstrate reproducible control of selected pore-network statistics and transport responses. However, agreement in geometry, porosity, or absolute permeability alone does not establish multiphase-flow equivalence. The principal barriers include limited reproducibly open pore-throat size, residual fabrication material, unstable or nonrepresentative surface wettability, incomplete 3D saturation and relative-permeability metrology, and insufficient durability under high-temperature, high-pressure, and reactive conditions. We therefore argue for task-specific equivalence under matched thermodynamic conditions and dimensionless flow parameters, with acceptance limits defined against natural-core measurements and experimental uncertainty. A closed workflow linking digital design, fabrication, post-fabrication imaging, microfluidic screening, core-scale validation, natural-core calibration, and numerical inversion can convert artificial porous media from morphological replicas into reproducible experimental surrogates.