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<p>This paper presents for the first time the trans-scale evaluation of the strengthening phenomena of a caprock shale due to the infiltration of oil-based nanoparticle suspension. The intact shale samples were first subject to injection of four different permeants, including pure water, pure oil, carbon black nanoparticle (CBN)-in-water suspension, and CBN-in-oil suspension, in a modified flexible wall permeameter, followed by big data nanoindentation (BDNi) to obtain the trans-scale Young’s modulus (<i>E</i>) and hardness (<i>H</i>) of both individual minerals at the microscale and the bulk rock at the mesoscale, accompanied by microstructure observations with scanning electron microscopy and elemental mapping. Results from infiltration tests indicate that the viscosity of CBN suspensions determines the infiltration rate, which is ~ 0.052 and ~ 0.019&#xa0;mL/day for water- and oil-based suspensions, respectively, while the solvent’s surface tension plays a secondary role although it helps dispersion of hydrophobic CBN. Microstructure characterizations reveal that nanoparticles are injected into the shale through a complex network of micropores and microcracks and function as a physical seal to block the defects. Comparison of the BDNi results from samples subject to different permeants shows that injection of water-based CBN suspension improves the <i>E</i> of the clay matrix and bulk rock by 9.0% and 13.6%, respectively, while the oil-based CBN suspension injection outperforms the aqueous counterpart, and the <i>E</i> of the clay matrix and bulk rock increases by 22.2% and 44.7%, respectively. The findings of this study can guide the practical application of nanoparticle injections to stabilize the wellbore in shale formations.</p>

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Trans-scale Evaluation of Strengthening of a Shale by Injecting Oil- and Water-Based Nanoparticle Suspensions

  • 期刊论文

  • 发表日期：

    2025年2月13日

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  • Yongkang Wu,
  • Yucheng Li,
  • Shengmin Luo,
  • Meng Lu,
  • Nancy Zhou,
  • Yuanzhi Qu,
  • Yuan Geng,
  • Guoping Zhang

摘要

This paper presents for the first time the trans-scale evaluation of the strengthening phenomena of a caprock shale due to the infiltration of oil-based nanoparticle suspension. The intact shale samples were first subject to injection of four different permeants, including pure water, pure oil, carbon black nanoparticle (CBN)-in-water suspension, and CBN-in-oil suspension, in a modified flexible wall permeameter, followed by big data nanoindentation (BDNi) to obtain the trans-scale Young’s modulus (E) and hardness (H) of both individual minerals at the microscale and the bulk rock at the mesoscale, accompanied by microstructure observations with scanning electron microscopy and elemental mapping. Results from infiltration tests indicate that the viscosity of CBN suspensions determines the infiltration rate, which is ~ 0.052 and ~ 0.019 mL/day for water- and oil-based suspensions, respectively, while the solvent’s surface tension plays a secondary role although it helps dispersion of hydrophobic CBN. Microstructure characterizations reveal that nanoparticles are injected into the shale through a complex network of micropores and microcracks and function as a physical seal to block the defects. Comparison of the BDNi results from samples subject to different permeants shows that injection of water-based CBN suspension improves the E of the clay matrix and bulk rock by 9.0% and 13.6%, respectively, while the oil-based CBN suspension injection outperforms the aqueous counterpart, and the E of the clay matrix and bulk rock increases by 22.2% and 44.7%, respectively. The findings of this study can guide the practical application of nanoparticle injections to stabilize the wellbore in shale formations.