Fractal Characteristics and Controlling Factors of Pore Structure in Marine-Continental Transitional Shale in the Shanxi Formation, Central Ordos Basin
- 1School of Petroleum Engineering and Environmental Engineering, Yan’an University, Yan’an 716000, China
Abstract
To examine the fractal characteristics and pore architectures within marine-continental transitional shale, experimental analyses were carried out for Shanxi shale samples collected from the central Ordos Basin. Multiple test approaches including scanning electron microscopy (SEM), X-ray diffraction analysis, total organic carbon (TOC) analysis, and gas adsorption experiments were applied in this work. According to experimental measurements, the mineral composition of collected Shanxi shale samples exhibits dominant quartz and clay minerals, averaging 38.2% and 54.36%, respectively, with an average TOC content of 1.635%. CO2-accessible micropores make an important contribution to specific surface area, whereas N2-accessible mesopore range pores contribute appreciably to pore volume. The pore size distribution is characterized by two dominant peaks within the ranges of 8–20 nm and 80–85 nm. Mineral pores constitute the primary pore type within Shanxi shale, while pores associated with organic matter are infrequently observed. Micropore-specific surface area parameters show positive correlative trends relative to TOC, yet only weak correlations exist between this parameter and quartz and clay minerals. Meso-macopore-specific surface area exhibits a negative correlative tendency versus TOC content, weakly correlated with clay minerals, and no relationship with quartz content. Pore volume magnitudes are predominantly controlled by organic matter abundance and clay mineral content, with quartz content having no significant impact. Fractal dimensions computed through the Frenkel–Halsey–Hill (FHH) model indicate that D1 values for the low-pressure interval vary between 2.654 and 2.834, and D2 corresponding to the high-pressure interval are distributed from 2.638 to 2.867. The internal pore structure’s complexity and heterogeneity are more pronounced than the surface roughness of the pores. Compared with typical marine and continental shales, marine-continental transitional shale displays intermediate characteristics in both pore morphology and fractal features. The key results demonstrate that TOC content has strong positive linkages with fractal dimensions D1 and D2. By contrast, clay minerals exhibit a marked negative association against D2. Quartz content does not show a significant correlation with D1, yet faint positive linkages are detected between this indicator and D2. The present work offers quantitative constraints to assess pore structure heterogeneity and gain insights into reservoir properties of marine-continental transitional shale.
Related
- Multifractal Characteristics and Factors Associated with Pore Structure in Taiyuan Formation Transitional Shales Based on LTNA and NMR
- Deformations and the controlling L∞-structure of extended Rota-Baxter Lie algebras
- Deformation theory and the controlling L∞-structure of extended Rota-Baxter algebras
- SN-ASMO: Satellite-Navigation Array Spatial-Manifold Precise Observation Theory A Mathematical Foundation for Observation Formation, Unified U(1) Geometry, Intrinsic Information, and Preservation of the RTK Integer Structure
- Effect of Turning Structure on Spatiotemporal Evolution Characteristics of Outburst Gas–Solid Two-Phase Flow Dynamic Disasters
BibTeX
@article{bai2026fractal,
title = {{Fractal Characteristics and Controlling Factors of Pore Structure in Marine-Continental Transitional Shale in the Shanxi Formation, Central Ordos Basin}},
author = {Xueqing Bai and Bangsheng Zhao and Bofu Ta and Siyuan Wang and Jin Han and Yanjun Wu and Gaorun Zhong},
journal = {Fractal and Fractional},
year = {2026},
month = oct,
doi = {10.3390/fractalfract10100714},
url = {https://www.mdpi.com/2504-3110/10/10/714},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Fractal Characteristics and Controlling Factors of Pore Structure in Marine-Continental Transitional Shale in the Shanxi Formation, Central Ordos Basin
AU - Xueqing Bai
AU - Bangsheng Zhao
AU - Bofu Ta
AU - Siyuan Wang
AU - Jin Han
AU - Yanjun Wu
AU - Gaorun Zhong
PY - 2026
DA - 2026/10/10
JO - Fractal and Fractional
DO - 10.3390/fractalfract10100714
UR - https://www.mdpi.com/2504-3110/10/10/714
AB - To examine the fractal characteristics and pore architectures within marine-continental transitional shale, experimental analyses were carried out for Shanxi shale samples collected from the central Ordos Basin. Multiple test approaches including scanning electron microscopy (SEM), X-ray diffraction analysis, total organic carbon (TOC) analysis, and gas adsorption experiments were applied in this work. According to experimental measurements, the mineral composition of collected Shanxi shale samples exhibits dominant quartz and clay minerals, averaging 38.2% and 54.36%, respectively, with an average TOC content of 1.635%. CO2-accessible micropores make an important contribution to specific surface area, whereas N2-accessible mesopore range pores contribute appreciably to pore volume. The pore size distribution is characterized by two dominant peaks within the ranges of 8–20 nm and 80–85 nm. Mineral pores constitute the primary pore type within Shanxi shale, while pores associated with organic matter are infrequently observed. Micropore-specific surface area parameters show positive correlative trends relative to TOC, yet only weak correlations exist between this parameter and quartz and clay minerals. Meso-macopore-specific surface area exhibits a negative correlative tendency versus TOC content, weakly correlated with clay minerals, and no relationship with quartz content. Pore volume magnitudes are predominantly controlled by organic matter abundance and clay mineral content, with quartz content having no significant impact. Fractal dimensions computed through the Frenkel–Halsey–Hill (FHH) model indicate that D1 values for the low-pressure interval vary between 2.654 and 2.834, and D2 corresponding to the high-pressure interval are distributed from 2.638 to 2.867. The internal pore structure’s complexity and heterogeneity are more pronounced than the surface roughness of the pores. Compared with typical marine and continental shales, marine-continental transitional shale displays intermediate characteristics in both pore morphology and fractal features. The key results demonstrate that TOC content has strong positive linkages with fractal dimensions D1 and D2. By contrast, clay minerals exhibit a marked negative association against D2. Quartz content does not show a significant correlation with D1, yet faint positive linkages are detected between this indicator and D2. The present work offers quantitative constraints to assess pore structure heterogeneity and gain insights into reservoir properties of marine-continental transitional shale.
SN - 2504-3110
ER -