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Clogging caused by particle migration during groundwater recharge in uncemented sandstone reservoir
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  • Fujian Yang,
  • Guiling Wang,
  • Hejuan liu,
  • Dawei Hu,
  • Hui Zhou
Fujian Yang
Institute of Rock and Soil Mechanics, Chinese Academy of Sciences
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Guiling Wang
Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences
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Hejuan liu
Institute of Rock and Soil Mechanics, Chinese Academy of Sciences
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Dawei Hu
Institute of Rock and Soil Mechanics, Chinese Academy of Sciences

Corresponding Author:[email protected]

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Hui Zhou
Institute of Rock and Soil Mechanics, Chinese Academy of Sciences
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Abstract

Clogging caused by grain migration during groundwater recharge is a critical problem for long-term operation period of Ground water-source heat pump (GWHP), especially for uncemented sandstone reservoir. Thus, the permeability tests of three groups of uncemented sandstone samples with different grain compositions are carried out respectively, under in-situ stress. The clogging caused by coupling effect of in-situ stress and grain-migration during groundwater recharge for uncemented sandstone. Firstly, the original grains are crushed even broken into fine grain under in-situ stress. Then, the fine grains originally filled or secondary crushed migrate along the space between skeleton structure and gradually deposit at the bottom of samples, resulting in the increase in pore pressure and the decrease in apparent permeability, which is in good agreement with the observations in the field. Apparent permeability exhibits different variation duo to the differences in grain composition, whilst the absolute permeability decreases with the increased grain size due to the compaction effect or/and the grain migration. Furthermore, the pore pressure increases with flow rate and tends to 1/2 of applied hydrostatic stress till the failure of samples. This indicates in-situ stress and pore pressure are key factors controlling the failure of uncemented sandstone, but excluding grain composition. The testing results in this context could facilitate our understanding of the clogging caused by coupling effect of in-situ stress and grain-migration during groundwater recharge for uncemented sandstone, and some suggestions could be provided for the utilization of hydrothermal geothermal energy especially for the uncemented sandstone reservoir.