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<p>Tight sandstone hydrocarbon resources are strategically important during the global energy transition. However, their small pore-throat sizes, complex pore-throat architectures, and strong heterogeneity produce large variations in seepage capacity and make efficient development difficult. The Chang 6 reservoir in the Ordos Basin is a representative low-permeability tight sandstone reservoir that requires detailed pore-structure characterization. In this study, mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) were integrated to characterize pore morphology, pore-throat distribution, and fluid occurrence. Compared with studies that mainly combine MIP, SEM, and NMR qualitatively, this work establishes a quantitatively coupled classification framework using K-means clustering and fractal descriptors, thereby enabling objective pore-type division and cross-method consistency analysis. Multi-scale characterization indicates that the Chang 6 tight sandstones can be classified into four pore-structure types. Type IV, defined as the high displacement pressure-fine throat type, is dominant in the study area. The NMR T₂ spectra show a bimodal distribution dominated by small pores, and movable fluid saturation is generally lower than 50%. The main contribution of this study is the integration of statistical clustering, multi-scale experimental constraints, and fractal geometry into a reproducible workflow for tight-sandstone pore-structure classification, rather than a simple juxtaposition of multiple experimental methods.</p>

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Fused characterization of pore structure classification in low-permeability tight sandstones

  • 期刊论文

  • 发表日期：

    2026年7月18日

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  • Yuling Zhang,
  • Changbing Huang,
  • Shengbo Yang,
  • Xinyu Zhu

摘要

Tight sandstone hydrocarbon resources are strategically important during the global energy transition. However, their small pore-throat sizes, complex pore-throat architectures, and strong heterogeneity produce large variations in seepage capacity and make efficient development difficult. The Chang 6 reservoir in the Ordos Basin is a representative low-permeability tight sandstone reservoir that requires detailed pore-structure characterization. In this study, mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) were integrated to characterize pore morphology, pore-throat distribution, and fluid occurrence. Compared with studies that mainly combine MIP, SEM, and NMR qualitatively, this work establishes a quantitatively coupled classification framework using K-means clustering and fractal descriptors, thereby enabling objective pore-type division and cross-method consistency analysis. Multi-scale characterization indicates that the Chang 6 tight sandstones can be classified into four pore-structure types. Type IV, defined as the high displacement pressure-fine throat type, is dominant in the study area. The NMR T₂ spectra show a bimodal distribution dominated by small pores, and movable fluid saturation is generally lower than 50%. The main contribution of this study is the integration of statistical clustering, multi-scale experimental constraints, and fractal geometry into a reproducible workflow for tight-sandstone pore-structure classification, rather than a simple juxtaposition of multiple experimental methods.