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<p>The mesoscopic damage mechanism during the penetration process of Polycrystalline Diamond Compact (PDC) bit remains poorly understood. This study developed a drillability model for tight sandstone that integrates heterogeneous digital rocks and 3D PDC micro-bits to simulate damage characteristics during dynamic drilling. Results show that confining pressure enhances intergranular friction and imposes interfacial constraints, thereby restricting initial rock failure and crack propagation. Microcracks under confining pressure constraints are difficult to propagate along intergranular boundaries and instead require the initiation of intragranular cracks to form a crack network. The total number of microcracks in the initial pitting stage at a confining pressure of 40 MPa is 3.6 times that under uniaxial conditions; however, in the stable rock-breaking stage, the proportion of shear cracks increases by approximately 31% compared to uniaxial conditions, indicating a tension–shear mixed failure mechanism under confining pressure. High-quartz sandstone exhibits elevated mineral hardness, which necessitates the formation of an intricate concentric crack network and continuous abrasion. Clay-rich sandstone exhibits low initial resistance but exhibits a crack growth of 348% during the intermediate penetration phase, characterized by a core-dense and edge-propagating pattern. Cement-rich sandstone exhibits gradual cement failure, with cracks transitioning from local to global. These findings offer meso‑mechanical insights for bit selection and design in tight sandstone. Moreover, the developed simulation platform provides a versatile digital alternative to traditional core-based drillability tests and supports customized bit design for different lithologies.</p>

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Construction and Application of a 3D PDC Micro-bit Cutting Model for Tight Sandstone Based on the Discrete Element Method

  • 期刊论文

  • 发表日期：

    2026年5月28日

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  • Yan Zhu,
  • Xu Yang,
  • Gao Li,
  • Jiaxin Feng,
  • Yi Zhang,
  • He Zhang

摘要

The mesoscopic damage mechanism during the penetration process of Polycrystalline Diamond Compact (PDC) bit remains poorly understood. This study developed a drillability model for tight sandstone that integrates heterogeneous digital rocks and 3D PDC micro-bits to simulate damage characteristics during dynamic drilling. Results show that confining pressure enhances intergranular friction and imposes interfacial constraints, thereby restricting initial rock failure and crack propagation. Microcracks under confining pressure constraints are difficult to propagate along intergranular boundaries and instead require the initiation of intragranular cracks to form a crack network. The total number of microcracks in the initial pitting stage at a confining pressure of 40 MPa is 3.6 times that under uniaxial conditions; however, in the stable rock-breaking stage, the proportion of shear cracks increases by approximately 31% compared to uniaxial conditions, indicating a tension–shear mixed failure mechanism under confining pressure. High-quartz sandstone exhibits elevated mineral hardness, which necessitates the formation of an intricate concentric crack network and continuous abrasion. Clay-rich sandstone exhibits low initial resistance but exhibits a crack growth of 348% during the intermediate penetration phase, characterized by a core-dense and edge-propagating pattern. Cement-rich sandstone exhibits gradual cement failure, with cracks transitioning from local to global. These findings offer meso‑mechanical insights for bit selection and design in tight sandstone. Moreover, the developed simulation platform provides a versatile digital alternative to traditional core-based drillability tests and supports customized bit design for different lithologies.