Clogging caused by particle migration during groundwater recharge in
uncemented sandstone reservoir
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.