Abstract
Pore–throat architecture governs fluid storage and multiphase transport in tight sandstone reservoirs, yet the mechanisms linking microscopic pore–throat characteristics to gas–water seepage behavior remain poorly constrained. Here, we establish a multi-scale structure–flow characterization framework by integrating mineralogical, petrographic, microscopic, capillary-pressure, and gas–water relative-permeability analyses to elucidate how pore–throat architecture controls reservoir flow behavior in the He 8 Member of the Ordos Basin. The results demonstrate that reservoir quality is governed primarily by the size, connectivity, and heterogeneity of effective throats rather than pore abundance alone. Although relatively limited in occurrence, large effective throats form preferential flow pathways that dominate permeability and gas mobility, whereas micropores primarily contribute to storage while intensifying capillary confinement and fluid retention. Accordingly, Type I reservoirs are characterized by well-developed effective throats, favorable connectivity, low irreducible water saturation, and broad gas–water co-flow intervals, whereas Type III reservoirs are dominated by fine and poorly connected pore–throat systems, strong capillary confinement, elevated irreducible water saturation, and restricted gas mobility. Effective throat radius, mercury withdrawal efficiency, and pore–throat heterogeneity emerge as the principal structural controls on irreducible water saturation, gas relative permeability, and two-phase flow capacity. These findings establish a mechanistic linkage from pore–throat architecture to fluid occurrence and seepage behavior, providing a structure–flow coupled framework that advances tight sandstone reservoir evaluation from static pore-space characterization toward dynamic assessment of flow capacity and development potential.
