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Abstract <p>The mechanical properties of deep shale are influenced by various factors, including high-temperature and high-pressure conditions, as well as its bedding structure. To investigate the evolution of mechanical properties of deep shale under different environmental temperatures, this study takes the Longmaxi Formation shale as an example, conducting high-temperature and high-pressure triaxial tests. Additionally, a thermal-mechanical coupled particle flow model for deep shale with a bedding structure is established from both macroscopic and mesoscopic perspectives. Based on X-ray diffraction experiments to determine the mineral composition and content of the shale, the model assigns the number of grouped mineral particles and their thermal expansion coefficients. Meanwhile, smooth joint contact is incorporated to characterize the influence of bedding structure, and the model’s mesoscopic parameters are calibrated using high-temperature and high-pressure triaxial test results. Based on the triaxial experiments and the thermal-mechanical coupled model, this study investigates the variations in mesoscopic thermal damage, rock mechanical properties, and failure modes of layered shale under different environmental temperatures. The results indicate that high temperature conditions weaken the mechanical properties of shale, while high confining pressure reduces the anisotropy of layered shale. As temperature increases, thermal damage initially occurs at the bedding interfaces. When the temperature exceeds 150°C, mineral particles undergo shear displacement, leading to a sparse distribution of mesoscopic force chains, and macroscopic thermal cracks expand extensively. In&#xa0;high-temperature and high-pressure environments, the thermal-mechanical coupling effect causes a reduction in the peak strength and an increase in peak strain, with the failure mode transitioning from brittle failure to plastic-ductile failure. Meanwhile, bedding cracks branch and gradually extend into the matrix, forming a composite failure mode involving both the shale matrix and the bedding structure.</p>

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Discrete Numerical Modeling of Macro-mesoscopic Mechanical Behaviors of Longmaxi Shale under High Temperature

  • 期刊论文

  • 发表日期：

    2025年6月1日

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  • Feng Sun,
  • Hengran Cao,
  • Zheng Liu,
  • Xudong Zhang,
  • Shifeng Xue

摘要

Abstract

The mechanical properties of deep shale are influenced by various factors, including high-temperature and high-pressure conditions, as well as its bedding structure. To investigate the evolution of mechanical properties of deep shale under different environmental temperatures, this study takes the Longmaxi Formation shale as an example, conducting high-temperature and high-pressure triaxial tests. Additionally, a thermal-mechanical coupled particle flow model for deep shale with a bedding structure is established from both macroscopic and mesoscopic perspectives. Based on X-ray diffraction experiments to determine the mineral composition and content of the shale, the model assigns the number of grouped mineral particles and their thermal expansion coefficients. Meanwhile, smooth joint contact is incorporated to characterize the influence of bedding structure, and the model’s mesoscopic parameters are calibrated using high-temperature and high-pressure triaxial test results. Based on the triaxial experiments and the thermal-mechanical coupled model, this study investigates the variations in mesoscopic thermal damage, rock mechanical properties, and failure modes of layered shale under different environmental temperatures. The results indicate that high temperature conditions weaken the mechanical properties of shale, while high confining pressure reduces the anisotropy of layered shale. As temperature increases, thermal damage initially occurs at the bedding interfaces. When the temperature exceeds 150°C, mineral particles undergo shear displacement, leading to a sparse distribution of mesoscopic force chains, and macroscopic thermal cracks expand extensively. In high-temperature and high-pressure environments, the thermal-mechanical coupling effect causes a reduction in the peak strength and an increase in peak strain, with the failure mode transitioning from brittle failure to plastic-ductile failure. Meanwhile, bedding cracks branch and gradually extend into the matrix, forming a composite failure mode involving both the shale matrix and the bedding structure.