Speaker
Description
Understanding the multiscale pore structure of high-porosity sandstone is essential for accurately modeling subsurface fluid transport. In this study, two sandstone cores (YS1 and YS2) were imaged using X-ray computed tomography (CT) at three voxel resolutions (50.8 μm, 21.6 μm, and 12 μm) to quantify scale-dependent pore morphology and its impact on permeability estimation. Across resolutions, we evaluated porosity, pore size distribution, pore-shape roughness, and fractal dimensions to characterize pore complexity and spatial heterogeneity. CT resolution strongly controls apparent pore visibility and connectivity. When the voxel size increases from 21.6 μm to 50.8 μm, total porosity drops markedly from 0.077/0.078 to 0.014/0.017 for YS1/YS2, respectively, indicating substantial loss of microporosity at coarse resolution. At 12 μm, connected pore volume fractions reach 10.37% (YS1-S) and 9.40% (YS2-S), close to total porosities of 12.64% and 12.23%, suggesting near-percolating pore networks at the finest scale. Consistently, pore-network modeling (PNM) is feasible only at 12 μm and yields absolute permeabilities of 1.94×10-12 m2 (YS1-S) and 3.65×10-12 m2 (YS2-S). To enable permeability quantification in under-resolved volumes where global percolation is absent (21.6 μm and 50.8 μm), we propose a local connectivity, sliding-layer approach. The CT volume is decomposed into overlapping three-slice unit layers; locally continuous pore segments within each unit are used to estimate layer permeability via simplified Hagen–Poiseuille assumptions, and bulk permeability is obtained through harmonic aggregation. The proposed method produces permeability estimates of 2.93×10-12 m2 (YS1-L), 2.76×10-12 m2 (YS1-M), 4.88×10-12 m2 (YS2-L), and 2.75×10-12 m2 (YS2-M), thereby bridging the resolution gap where conventional PNM fails. Although simulated permeabilities remain higher than laboratory gas permeability measurements, the framework provides a scalable pathway linking multiscale structure descriptors to flow estimation under realistic connectivity constraints, with implications for digital rock physics and upscaling.
| Country | China |
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