CT imaging-based characterization of multiscale pore heterogeneity and fluid flow in sandstone and conglomerate

Abstract

Heterogeneity in geologic media significantly influences fluid flow characteristics, with scale-dependent effects playing a crucial role in subsurface fluid flow behavior. This study investigates core- and pore-scale heterogeneities in Entrada Sandstone and Janggi Conglomerate using multi-resolution X-ray CT imaging (voxel resolutions: 1.625, 28, 40, and 58 μm). Petrophysical properties—including porosity, permeability, and pore structure characteristics—were evaluated to understand their influence on fluid flow. Through detailed pore structure and flow analyses, this study captured core-scale geologic heterogeneities such as cross-laminae in Entrada Sandstone and clast distributions in Janggi Conglomerate, as well as pore-scale variations in textural maturity. These heterogeneities influenced fluid flow characteristics differently at each scale. In Janggi Conglomerate, well-developed pore spaces along clast surfaces were identified as important flow pathways, which could mitigate overpressure and provide additional storage capacity during fluid injection. Additionally, pore-filling minerals within the matrix contributed to capillary heterogeneity, which could strongly influence multi-phase flow behavior. These findings emphasize that geologic heterogeneities influence fluid flow differently across rock types and spatial scales. By examining heterogeneity separately at core and pore scales, this study provides a detailed characterization of fluid flow behavior, offering insights for reservoir assessment and subsurface fluid flow evaluation.