Heterogeneity of Pore and Fracture Structure in Coal Reservoirs by Using High-Pressure Mercury Intrusion and Removal Curve
Abstract
:1. Introduction
2. Experimental Testing and Fractal Theory
2.1. Sample Preparation and Experimental Test
2.2. Fractal Theory
3. Results and Discussion
3.1. Pore Distribution Based on High-Pressure Mercury Injection Test
3.2. Refined Description of Pore Structure Distribution Heterogeneity Based on the Mercury Inlet Curve
3.3. Quantitative Characterization of Pore Structure Distribution Heterogeneity Based on the Mercury Removal Curve
3.4. Influencing Factors Restricting Pore Fractal Characteristics and Applicability Analysis
4. Conclusions
- (1)
- Samples can be divided into two categories according to porosity and mercury removal efficiency. Among them, the mercury removal efficiency of type A (see Figure 1 for details) is higher than 35%, and the porosity is less than 9.5%, while those of type B (see Figure 1 for details) are the opposite. The seepage pore volume percentage of type A is 35–60%, which is higher than that of type B. In general, type A developed seepage pores, while type B developed adsorption pores.
- (2)
- Fractal characteristics of the mercury inlet curve. The difference of the samples’ fractal dimension calculated with the Menger and Sierpinski models is small, indicating that the pore structure distribution heterogeneity of the two types is similar. The multifractal model shows that the adsorption pore and macro-pore heterogeneity of type B is stronger than that of type A, and the pore distribution heterogeneity is controlled by the low value of the pore volume.
- (3)
- Fractal characteristics of the mercury removal curve. The results of the two single fractal calculations show that the pore structure distribution heterogeneity of type B is stronger than that of type A. The multifractal model calculation shows that the adsorption pore distribution heterogeneity of type B is stronger, and the low value of the pore volume controls the pore distribution heterogeneity, which is consistent with the results of the mercury inlet fractal.
- (4)
- The mercury fractals based on the Menger model can reflect the adsorption pore distribution and macro-pore distribution heterogeneity, while the Sierpinski model can only reflect the adsorption pore distribution heterogeneity at the mercury inlet stage. The physical meanings revealed by the single–multiple fractal parameters based on the mercury curve are different, and the physical meanings are different.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
Abbreviations
LPCO2GA | Carbon dioxide adsorption test |
HPMI | High-pressure mercury injection test |
LPN2GA | Low-temperature liquid nitrogen test |
LF-NMR | Low-field nuclear magnetic resonance technology |
M model | Menger models |
MIC | Mercury injection curve |
MRC | Mercury removal curve |
PFDH | Pore and fracture distribution heterogeneity |
S model | Sierpinski models |
FE-SEM | Scanning electron microscopy |
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Sample Number | Pore Volume Percentage | ||
---|---|---|---|
1000–10,000 nm | 100–1000 nm | <100 nm | |
Sample 1 | 0.306338 | 0.60915493 | 0.084507 |
Sample 2 | 0.518116 | 0.35144928 | 0.130435 |
Sample 3 | 0.483871 | 0.35483871 | 0.16129 |
Sample 4 | 0.320833 | 0.35 | 0.329167 |
Sample 5 | 0.339902 | 0.300492 | 0.359606 |
Sample 6 | 0.608924 | 0.26509126 | 0.125985 |
Sample 7 | 0.728643 | 0.2361807 | 0.035176 |
Sample 8 | 0.639567 | 0.30894289 | 0.05149 |
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Niu, Z.; Li, J.; Yao, P.; Zhang, J.; Sun, S.; Liu, W.; Cui, S.; Sun, J. Heterogeneity of Pore and Fracture Structure in Coal Reservoirs by Using High-Pressure Mercury Intrusion and Removal Curve. Processes 2023, 11, 3120. https://doi.org/10.3390/pr11113120
Niu Z, Li J, Yao P, Zhang J, Sun S, Liu W, Cui S, Sun J. Heterogeneity of Pore and Fracture Structure in Coal Reservoirs by Using High-Pressure Mercury Intrusion and Removal Curve. Processes. 2023; 11(11):3120. https://doi.org/10.3390/pr11113120
Chicago/Turabian StyleNiu, Zhixiang, Jie Li, Peng Yao, Junjian Zhang, Shuang Sun, Wenlong Liu, Shuangshuang Cui, and Jingli Sun. 2023. "Heterogeneity of Pore and Fracture Structure in Coal Reservoirs by Using High-Pressure Mercury Intrusion and Removal Curve" Processes 11, no. 11: 3120. https://doi.org/10.3390/pr11113120