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<p>Revealing the evolution and microscopic mechanism of fractures in heterogeneous conglomerates is critical for the development of conglomerate reservoirs. This study establishes a real gravel contour database and develops a technology for random delivery of gravel and a discrete element model, to explicitly characterize conglomerate geometric heterogeneity. Through triaxial compression simulation under varying confining pressures, the influence of gravel microstructure on dynamic crack propagation is analyzed. The failure mode of conglomerate transitions from tensile failure under uniaxial condition to shear failure under low confining pressure and cataclastic flow under high confining pressure. Failure behavior is controlled by both local stress concentration induced by gravel heterogeneity and external loads, exhibiting distinct stage characteristics. During the elastic stage, concentrations of tensile and shear stress develop at the cementation surfaces of gravel edge and adjacent gravel contact points, initiating microcracks. In the plastic stage, cracks propagate into the gravel and matrix, with high tensile and shear stresses emerging at the gravel edges and interiors. Gravel boundary cracks, primarily controlled by the geometry and distribution of gravel, may converge to form “Y” or “wing” cracks. Gravel-penetrating cracks, controlled by external loading, propagate based on gravel curvature: cracks penetrate gravels with similar curvature, while propagating toward gravels of smaller curvature when the curvature differences is significant, forming multiple clusters of cracks. During peak and post-peak stages, tensile or shear stress regions coalesce, causing microcracks to aggregate into main fractures that propagating along boundary stress directions. Increasing confining pressure enhances specimen damage, promoting shear fractures formation.</p>

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Micro-Mechanical Analysis of the Failure Process of Conglomerate: Insights from DEM Simulation with Physics-Based Gravel Structure

  • 期刊论文

  • 发表日期：

    2025年5月8日

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  • Kang Duan,
  • Luchao Wang,
  • Jiarun Li,
  • Qiangyong Zhang,
  • Xuejian Li,
  • Rihua Jiang

摘要

Revealing the evolution and microscopic mechanism of fractures in heterogeneous conglomerates is critical for the development of conglomerate reservoirs. This study establishes a real gravel contour database and develops a technology for random delivery of gravel and a discrete element model, to explicitly characterize conglomerate geometric heterogeneity. Through triaxial compression simulation under varying confining pressures, the influence of gravel microstructure on dynamic crack propagation is analyzed. The failure mode of conglomerate transitions from tensile failure under uniaxial condition to shear failure under low confining pressure and cataclastic flow under high confining pressure. Failure behavior is controlled by both local stress concentration induced by gravel heterogeneity and external loads, exhibiting distinct stage characteristics. During the elastic stage, concentrations of tensile and shear stress develop at the cementation surfaces of gravel edge and adjacent gravel contact points, initiating microcracks. In the plastic stage, cracks propagate into the gravel and matrix, with high tensile and shear stresses emerging at the gravel edges and interiors. Gravel boundary cracks, primarily controlled by the geometry and distribution of gravel, may converge to form “Y” or “wing” cracks. Gravel-penetrating cracks, controlled by external loading, propagate based on gravel curvature: cracks penetrate gravels with similar curvature, while propagating toward gravels of smaller curvature when the curvature differences is significant, forming multiple clusters of cracks. During peak and post-peak stages, tensile or shear stress regions coalesce, causing microcracks to aggregate into main fractures that propagating along boundary stress directions. Increasing confining pressure enhances specimen damage, promoting shear fractures formation.