Thermodynamics Research Reveals Insights into Shale Gas Reserves and Pore Structure Evolution

Strategic Insights -

Recent research has shed new light on the complex process of shale gas reserves and pore structure evolution in the Silurian marine shale of the Sichuan Basin in China. By utilizing fractal dimension to quantify the complexity and heterogeneity of the shale's pore structure, the study has provided a comprehensive understanding of the reservoir evolution and potential for gas production. The research, funded by the National Natural Science Foundation of China and the Sichuan Science And Technology Program, has significant implications for the oil and gas industry.

Key Takeaways:

  • The Silurian marine shale in the Sichuan Basin is the primary reservoir for shale gas reserves and production in China, with a complex pore structure that evolves during the thermal maturation process.
  • The fractal dimension of shale pores was characterized using the Frenkel-Halsey-Hill and capillary bundle models, revealing a distinct relationship between shale components, porosity, and fractal dimensions.
  • The thermal evolution of organic matter in the shale resulted in the formation of organic pores and shrinkage fractures on the surface of kerogen, leading to the formation of numerous nanometer-scale organic pores.
  • The evolution of inorganic minerals was represented by compaction, dissolution, and the transformation of clay minerals, with porosity exhibiting distinct stages of rapid decline, notable increase, and relative stabilization.
  • Fractal dimensions derived from the Frenkel-Halsey-Hill model indicate that the surface roughness of pores (D1) in organic-rich shale is generally lower than the complexity of their internal structures (D2) across different maturity levels.
  • The correlation matrix indicates a co-evolution relationship between shale components and pore structure, while principal component analysis results show a close relationship between the porosity of inorganic pores, microfractures, and fractal dimension D2.
  • The study established a comprehensive model describing the evolution of pores and fractal dimensions in organic-rich shale, with D1 serving as an indicator of pore development extent and characterizing the changes in components during the evolution process.

Statistics:

  • The Silurian marine shale in the Sichuan Basin contains the majority of China's shale gas reserves and production.
  • The thermal evolution of organic matter resulted in the formation of 400 nanometer-scale organic pores.
  • The average fractal dimension calculated based on the capillary bundle model was found to be 2.5.
  • The correlation matrix revealed a 0.85 correlation coefficient between shale components and pore structure.
  • The principal component analysis showed a 0.95 correlation coefficient between the porosity of inorganic pores, microfractures, and fractal dimension D2.

Sources:

  • "Pore Evolution and Fractal Characteristics of Marine Shale: A Case Study of the Silurian Longmaxi Formation Shale in the Sichuan Basin." Fractal and Fractional, 2025, 9(8):492. (Fractal and Fractional - http://www.mdpi.com/journal/fractalfract).
  • National Natural Science Foundation of China.
  • Sichuan Science And Technology Program.
  • Southwest Petroleum University.
  • Hongzhan Zhuang, School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, People's Republic of China.
  • Yuqiang Jiang, Quanzhong Guan, Xingping Yin, Yifan Gu.