Pore Structure and Factors Controlling Shale Reservoir Quality: A Case Study of Chang 7 Formation in the Southern Ordos Basin, China
Abstract
:1. Introduction
2. Geological Setting
3. Samples and Methods
4. Results
4.1. Mineral Compositions and Lithofacies Classification
4.2. Organic Geochemistry Classification
4.3. Porosity
4.4. Pore Types
4.5. Quantitative Analyses of Pore Structure
4.5.1. Pore Structure Characterized by Nitrogen Adsorption (NA)
4.5.2. Pore Structure Characterized by High-Pressure Mercury Injection (HPMI)
5. Discussion
5.1. PSD Characteristics Integrated NA and HPMI
5.2. Effective Pore Type
5.3. Main Controlling Factors on Reservoir Quality
5.3.1. Influence of Organic Matter on Reservoir Quality
5.3.2. Influence of Mineral Composition on Reservoir Quality
5.3.3. Influence of Lithofacies on Reservoir Quality
6. Conclusions
- (1)
- The shale reservoir can be divided into five lithofacies using the ternary diagrams of TOC, argillaceous minerals, and siliceous minerals: high organic-rich siliceous shale (HOSS); high organic-rich argillaceous shale (HOAS); medium organic-rich siliceous shale (MOSS); medium organic-rich argillaceous shale (MOAS); and low organic-rich shale (LOS). The organic matter type is mainly Type I to Type II kerogen in the study area, predominantly Type II1 kerogen. Most of the samples lie within the mature stage of hydrocarbon generation.
- (2)
- Various types of pores were identified in the studied shale: intergranular pores, intragranular pores, intercrystalline pores, organic matter pores, and seams around organic matter. The pores are commonly nanoscale to micrometer in scale, with diameters ranging from 10 nm to a few microns. The NA and HPMI experimental results were integrated to analyze the characteristics of the PSD. The contents of macropore in MOSS, MOAS, and LOS decrease sequentially while the contents of mesopore increase sequentially.
- (3)
- The S1 content in shale is positively correlated with the macropore content, indicating that macropores in shale are the main effective oil storage space and are important for oil-bearing reservoirs.
- (4)
- There is a good positive relationship between shale macropore volume and organic matter content. Organic matter in the shale can be beneficial for generating organic matter pores, dissolution pores, and organic matter edge seams, resulting in better physical properties of shale reservoirs. The samples have a negative relationship between the quartz/feldspar content and macropores content, indicating that quartz and feldspar are adverse for the development of macropores. The lithofacies is one of the important controlling factors for the development of macropores. MOAS and HOAS are favorable lithofacies for the development of macropores.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Li, Q.; You, X.; Li, J.; Zhou, Y.; Lu, H.; Wu, S.; Yue, D.; Zhang, H. Pore Structure and Factors Controlling Shale Reservoir Quality: A Case Study of Chang 7 Formation in the Southern Ordos Basin, China. Energies 2024, 17, 1140. https://doi.org/10.3390/en17051140
Li Q, You X, Li J, Zhou Y, Lu H, Wu S, Yue D, Zhang H. Pore Structure and Factors Controlling Shale Reservoir Quality: A Case Study of Chang 7 Formation in the Southern Ordos Basin, China. Energies. 2024; 17(5):1140. https://doi.org/10.3390/en17051140
Chicago/Turabian StyleLi, Qing, Xuelian You, Jiangshan Li, Yuan Zhou, Hao Lu, Shenghe Wu, Dali Yue, and Houmin Zhang. 2024. "Pore Structure and Factors Controlling Shale Reservoir Quality: A Case Study of Chang 7 Formation in the Southern Ordos Basin, China" Energies 17, no. 5: 1140. https://doi.org/10.3390/en17051140
APA StyleLi, Q., You, X., Li, J., Zhou, Y., Lu, H., Wu, S., Yue, D., & Zhang, H. (2024). Pore Structure and Factors Controlling Shale Reservoir Quality: A Case Study of Chang 7 Formation in the Southern Ordos Basin, China. Energies, 17(5), 1140. https://doi.org/10.3390/en17051140