Multiscale Characterization of Pore Structure and Heterogeneity in Deep Marine Qiongzhusi Shales from Southern Basin, China
Abstract
:1. Introduction
2. Geological Setting
3. Materials and Methods
3.1. Materials
3.2. TOC and Mineralogical Experiments
3.3. Scanning Electron Microscopy (SEM)
3.4. CO2 Adsorption–Desorption Experiments
3.5. N2 Adsorption–Desorption Experiments
3.6. High-Pressure Mercury Injection Experiments
3.7. Fractal Dimension Calculation
4. Results
4.1. TOC and Mineralogy
4.2. Pore Types and Morphological Characteristics
4.3. Pore Structure and Pore Size Distribution
4.4. Fractal Dimensions
5. Discussion
5.1. The Coupling Mechanism Between Pore Structure Parameters
5.2. The Influence of Heterogeneity on Pore Structure
5.3. Compositional Controls on Pore Structure
5.4. Compositional Controls on Heterogeneity
6. Conclusions
- The pore size distribution of Qiongzhusi shale exhibits a complex, bimodal pattern in the <10 nm range, indicating that smaller pores significantly contribute to the total pore volume and specific surface area. The pore volume in the 10–100 nm range remained relatively stable, with minimal variation among samples.
- In comparison to Longmaxi shale (moderate maturity, Ro: 2.5–3.0%), Qiongzhusi shale has experienced excessive thermal evolution, leading to the collapse of organic pores and a reduction in micropore abundance and specific surface area. The pore system of Qiongzhusi shale is predominantly composed of inorganic pores.
- The fractal dimension of the Qiongzhusi shale samples is notably high (ranging from 2.701 to 2.811, with an average of 2.775), suggesting a highly complex and heterogeneous pore structure. This complexity may be attributed to multistage tectonic evolution, intricate mineral composition, diverse pore types, and a wide range of pore sizes, all of which enhance the heterogeneity and fractal characteristics of the pores.
- A strong linear correlation was observed between total porosity and total pore volume, as well as between specific surface area and pore volume of micropores, mesopores, and macropores. These relationships underscore the critical role of pore volume in influencing porosity and specific surface area. Conversely, a weak positive correlation between porosity and TOC content indicates that the contribution of organic matter to pore development is limited. Additionally, carbonate and clay minerals exhibit a significant negative correlation with porosity, reflecting their detrimental effects on pore preservation through processes of cementation and compaction.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Sample ID | Depth/m | TOC/% | Feldspar | Quartz | Calcite | Dolomite | Gypsum | Pyrite | Clays | Others |
---|---|---|---|---|---|---|---|---|---|---|
Z201-1 | 4573.41 | 2.08 | 16.4 | 39.0 | 2.4 | 2.8 | / | 3.5 | 35.0 | 0.9 |
Z201-2 | 4579.10 | 1.59 | 18.0 | 36.9 | 3.1 | 2.1 | 1.1 | 3.8 | 34.1 | 0.9 |
Z201-4 | 4589.70 | 1.67 | 23.6 | 38.2 | 2.6 | 1.7 | / | 3.7 | 29.3 | 0.9 |
Z201-6 | 4604.00 | 4.57 | 21.8 | 41.1 | 2.4 | 2.8 | 1.3 | 5.8 | 23.9 | 0.9 |
Z201-8 | 4610.94 | 2.37 | 22.4 | 31.2 | 5.2 | 1.5 | 1.4 | 5.5 | 32.1 | 0.7 |
Z201-10 | 4620.54 | 0.329 | 24.9 | 32.8 | 1.2 | 4.3 | / | 5.2 | 30.7 | 0.9 |
Z201-11 | 4745.32 | 2.00 | 18.2 | 48.0 | 5.0 | 1.3 | 1.1 | 3.3 | 23.1 | 0.0 |
Z201-12 | 4750.05 | 2.74 | 23.0 | 36.0 | 0.8 | 4.5 | 0.9 | 4.8 | 29.3 | 0.7 |
Z201-14 | 4774.36 | 1.72 | 19.0 | 48.2 | 7.2 | 0.8 | / | 2.8 | 22.0 | 0.0 |
Z201-16 | 4796.00 | 5.24 | 16.0 | 56.1 | 4.9 | 1.3 | / | 2.8 | 18.9 | 0.0 |
Z201-18 | 4805.09 | 3.56 | 18.9 | 41.4 | 1.5 | 4.9 | / | 3.6 | 29.7 | 0.0 |
Z201-20 | 4810.94 | 3.12 | 17.0 | 38.8 | 2.7 | 4.5 | 0.9 | 4.4 | 31.2 | 0.5 |
Sample ID | Porosity | Pore Volume (cm3/g) | Specific Surface Area (m2/g) | Total Pore Volume (cm3/g) | Total Specific Surface Area (m2/g) | Average Pore Diameter (nm) | ||||
---|---|---|---|---|---|---|---|---|---|---|
Micropore | Mesopore | Macropore | Micropore | Mesopore | Macropore | |||||
Z201-1 | 4.30 | 0.0047 | 0.0089 | 0.0011 | 11.6913 | 13.5180 | 1.7545 | 0.0147 | 26.96 | 0.8116 |
Z201-2 | 3.74 | 0.0048 | 0.0072 | 0.0006 | 11.4692 | 10.9810 | 0.4664 | 0.0125 | 22.92 | 1.0265 |
Z201-4 | 3.61 | 0.0044 | 0.0114 | 0.0007 | 10.6194 | 13.6150 | 0.8580 | 0.0165 | 25.09 | 2.3071 |
Z201-6 | 5.08 | 0.0072 | 0.0134 | 0.0005 | 17.7394 | 22.8170 | 0.4670 | 0.0212 | 41.02 | 1.1853 |
Z201-8 | 4.70 | 0.0041 | 0.0084 | 0.0006 | 10.3071 | 13.2660 | 0.7346 | 0.0132 | 24.31 | 0.0004 |
Z201-10 | 1.13 | 0.0019 | 0.0031 | 0.0004 | 4.5532 | 3.9290 | 0.5530 | 0.0054 | 9.04 | 0.5953 |
Z201-11 | 2.91 | 0.0033 | 0.0058 | 0.0007 | 8.1804 | 8.8690 | 0.7460 | 0.0098 | 17.80 | 0.0003 |
Z201-12 | 3.21 | 0.0051 | 0.0066 | 0.0007 | 12.5063 | 12.6080 | 0.8560 | 0.0124 | 25.97 | 1.0301 |
Z201-14 | 2.58 | 0.0033 | 0.0054 | 0.0008 | 8.2447 | 8.7870 | 1.2340 | 0.0096 | 18.27 | 1.0886 |
Z201-16 | 4.38 | 0.0077 | 0.0112 | 0.0004 | 19.1829 | 21.7570 | 0.4286 | 0.0193 | 41.37 | 0.0004 |
Z201-18 | 3.49 | 0.0060 | 0.0079 | 0.0003 | 15.0056 | 16.1960 | 0.2340 | 0.0143 | 31.44 | 0.6588 |
Z201-20 | 3.47 | 0.0055 | 0.0064 | 0.0004 | 13.7491 | 14.5040 | 0.3520 | 0.0123 | 28.61 | 2.0018 |
Sample ID | Fractal Fitting Equation | D | R2 | Sample ID | Fractal Fitting Equation | D | R2 |
---|---|---|---|---|---|---|---|
Z201-1 | y = −0.213x + 1.50 | 2.787 | 0.959 | Z201-11 | y = −0.244x + 1.05 | 2.756 | 0.927 |
Z201-2 | y = −0.217x + 1.27 | 2.783 | 0.921 | Z201-12 | y = −0.223x + 1.40 | 2.777 | 0.926 |
Z201-4 | y = −0.191x + 0.325 | 2.809 | 0.877 | Z201-14 | y = −0.247x + 1.02 | 2.753 | 0.923 |
Z201-6 | y = −0.189x + 1.53 | 2.811 | 0.849 | Z201-16 | y = −0.234x +1.93 | 2.766 | 0.888 |
Z201-8 | y = −0.230x + 1.43 | 2.77 | 0.914 | Z201-18 | y = −0.219x + 1.63 | 2.781 | 0.881 |
Z201-10 | y = −0.299x + 1.46 | 2.701 | 0.933 | Z201-20 | y = −0.242x + 1.97 | 2.758 | 0.914 |
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Zheng, M.; Chen, Y.; Tang, T.; Wu, Y.; Chen, Y.; Chen, J.; Peng, S.; Zhang, J. Multiscale Characterization of Pore Structure and Heterogeneity in Deep Marine Qiongzhusi Shales from Southern Basin, China. Minerals 2025, 15, 515. https://doi.org/10.3390/min15050515
Zheng M, Chen Y, Tang T, Wu Y, Chen Y, Chen J, Peng S, Zhang J. Multiscale Characterization of Pore Structure and Heterogeneity in Deep Marine Qiongzhusi Shales from Southern Basin, China. Minerals. 2025; 15(5):515. https://doi.org/10.3390/min15050515
Chicago/Turabian StyleZheng, Majia, Yana Chen, Tingke Tang, Ya Wu, Ying Chen, Junyu Chen, Shixuan Peng, and Jizhen Zhang. 2025. "Multiscale Characterization of Pore Structure and Heterogeneity in Deep Marine Qiongzhusi Shales from Southern Basin, China" Minerals 15, no. 5: 515. https://doi.org/10.3390/min15050515
APA StyleZheng, M., Chen, Y., Tang, T., Wu, Y., Chen, Y., Chen, J., Peng, S., & Zhang, J. (2025). Multiscale Characterization of Pore Structure and Heterogeneity in Deep Marine Qiongzhusi Shales from Southern Basin, China. Minerals, 15(5), 515. https://doi.org/10.3390/min15050515