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<p>The influence of shale hydration on its mechanical properties is a critical issue in wellbore stability and hydraulic fracturing engineering. This study employs in-situ uniaxial compression CT scanning technology combined with digital volume correlation (DVC) to systematically investigate the influence mechanism of different hydration times (0, 2, 5, 30&#xa0;days) on damage evolution of Longmaxi Formation shale. Results indicate that the initial spatial distribution of hydration-induced fractures is the key factor controlling subsequent mechanical responses. Initial fractures generated by short-term hydration (2&#xa0;days) primarily develop within the matrix. During axial loading, these fractures undergo compaction and closure due to lateral confinement formed by loosening of bedding weak planes, exhibiting a dynamic structural optimization effect of damage-compaction-strengthening, which results in anomalous enhancement of elastic modulus and peak strength and delays specimen destabilization and failure. With extended hydration duration (≥ 5&#xa0;days), water forms interconnected weakening zones along bedding planes, and crack propagation transitions from stress-driven mixed fracture to structure-controlled bedding-parallel splitting, leading to significant degradation of rock mechanical properties. Additionally, hydration intensifies the anisotropic evolution of pore-fracture structures, resulting in significantly increased anisotropy of mechanical responses. This study elucidates the staged evolution characteristics and mesoscopic mechanisms of shale hydration damage, providing quantitative experimental evidence for evaluating the influence of hydration time effects on shale stability.</p>

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Investigation on the Mechanism of Hydration Time Effect on Damage Evolution in Shale Based on CT-DVC

  • 期刊论文

  • 发表日期：

    2025年12月24日

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  • Liang Zhang,
  • Yingjie Li,
  • Liu Yang,
  • Shengxin Liu,
  • Bingqian Wang

摘要

The influence of shale hydration on its mechanical properties is a critical issue in wellbore stability and hydraulic fracturing engineering. This study employs in-situ uniaxial compression CT scanning technology combined with digital volume correlation (DVC) to systematically investigate the influence mechanism of different hydration times (0, 2, 5, 30 days) on damage evolution of Longmaxi Formation shale. Results indicate that the initial spatial distribution of hydration-induced fractures is the key factor controlling subsequent mechanical responses. Initial fractures generated by short-term hydration (2 days) primarily develop within the matrix. During axial loading, these fractures undergo compaction and closure due to lateral confinement formed by loosening of bedding weak planes, exhibiting a dynamic structural optimization effect of damage-compaction-strengthening, which results in anomalous enhancement of elastic modulus and peak strength and delays specimen destabilization and failure. With extended hydration duration (≥ 5 days), water forms interconnected weakening zones along bedding planes, and crack propagation transitions from stress-driven mixed fracture to structure-controlled bedding-parallel splitting, leading to significant degradation of rock mechanical properties. Additionally, hydration intensifies the anisotropic evolution of pore-fracture structures, resulting in significantly increased anisotropy of mechanical responses. This study elucidates the staged evolution characteristics and mesoscopic mechanisms of shale hydration damage, providing quantitative experimental evidence for evaluating the influence of hydration time effects on shale stability.