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<p>While low-maturity shale oil resources possess substantial potential, the inherent heterogeneity of reservoir pores significantly impedes their efficient exploitation. Consequently, a comprehensive elucidation of their pore multifractal characteristics and the underlying governing factors becomes paramount for successful exploration and optimal resource development. This investigation focused on the Shahejie Formation fourth member (E<i>s</i>4) shale within the Liaohe Western Depression of the Bohai Bay Basin. A comprehensive suite of analytical techniques, including total organic carbon (TOC) analysis, rock-eval pyrolysis, physical property measurements, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and nuclear magnetic resonance (NMR), was employed. it specifically characterizes their pore structure and multifractal attributes, subsequently analyzing the governing factors and implications for resource exploitation. The findings indicate that the pore system within the low maturity E<i>s</i>4 shale is predominantly composed of intergranular mineral pores, interlayer clay mineral pores, and microfractures. Dissolution pores are sparsely developed, and organic matter pores are virtually absent. Mesopores (2–50&#xa0;nm) and macropores (&gt; 50&#xa0;nm) collectively constitute over 90% of the total pore volume. The pore size distribution manifests pronounced multifractal characteristics, with a multifractal spectrum width ranging from 2.05 to 12.07 (average: 7.47). The low maturity of organic matter leads to insufficient generation of organic acids, and diagenesis occurs in an alkaline environment, which limits dissolution. As a result, the correlations between mineral components such as quartz, calcite, feldspar and multifractal parameters are not significant. Furthermore, significant differences in pore connectivity also result in non-significant correlations between multifractal parameters and the bulk physical properties of shale. Furthermore, the pore structure, predominantly characterized by mesopores and macropores, not only facilitates the presence of free oil but also supports the implementation of techniques such as heat and gas injection, thereby contributing to an improved recovery rate for the low maturity Es4 shale oil. This study elucidates the multifractal characteristics of pores in low maturity shale and the factors influencing them, which can provide guidance for the exploration and development of low maturity shale oil.</p>

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Pore structure multifractal of low-maturity shale reservoirs in the Liaohe Western Depression, Bohai Bay basin

  • 期刊论文

  • 发表日期：

    2026年1月12日

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  • Xin He,
  • Ruifei Wang,
  • Xuejuan Zhang,
  • Lei Zhang,
  • Rongjin Gao,
  • Ruhao Liu,
  • Wenwen Lei

摘要

While low-maturity shale oil resources possess substantial potential, the inherent heterogeneity of reservoir pores significantly impedes their efficient exploitation. Consequently, a comprehensive elucidation of their pore multifractal characteristics and the underlying governing factors becomes paramount for successful exploration and optimal resource development. This investigation focused on the Shahejie Formation fourth member (Es4) shale within the Liaohe Western Depression of the Bohai Bay Basin. A comprehensive suite of analytical techniques, including total organic carbon (TOC) analysis, rock-eval pyrolysis, physical property measurements, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and nuclear magnetic resonance (NMR), was employed. it specifically characterizes their pore structure and multifractal attributes, subsequently analyzing the governing factors and implications for resource exploitation. The findings indicate that the pore system within the low maturity Es4 shale is predominantly composed of intergranular mineral pores, interlayer clay mineral pores, and microfractures. Dissolution pores are sparsely developed, and organic matter pores are virtually absent. Mesopores (2–50 nm) and macropores (> 50 nm) collectively constitute over 90% of the total pore volume. The pore size distribution manifests pronounced multifractal characteristics, with a multifractal spectrum width ranging from 2.05 to 12.07 (average: 7.47). The low maturity of organic matter leads to insufficient generation of organic acids, and diagenesis occurs in an alkaline environment, which limits dissolution. As a result, the correlations between mineral components such as quartz, calcite, feldspar and multifractal parameters are not significant. Furthermore, significant differences in pore connectivity also result in non-significant correlations between multifractal parameters and the bulk physical properties of shale. Furthermore, the pore structure, predominantly characterized by mesopores and macropores, not only facilitates the presence of free oil but also supports the implementation of techniques such as heat and gas injection, thereby contributing to an improved recovery rate for the low maturity Es4 shale oil. This study elucidates the multifractal characteristics of pores in low maturity shale and the factors influencing them, which can provide guidance for the exploration and development of low maturity shale oil.