This study presented the effect of polymer adsorption-induced permeability reduction on oil recovery,
particularly in low permeability system. The polymer injecting experiments were conducted in a quarter
of five-spot pattern with concentrations generally applied. Especially, by using the field oriented twodimensional
sandstone, we attempted to analyze the combined effect of polymer retention for concentration
and high velocity near injection on oil recovery.
Particularly in low permeable sandstone, oil recovery was not proportionally enhanced with increase
in polymer concentration, rather decreased at concentrations above 1,000 ppm in this experiment. This
could be understood by polymer adsorption phenomena corresponding to concentrations. The polymer
adsorption layer formed at high concentration clogged effective pore radius by up to 59.8%, compared to
clean sandstone and the permeability greatly decreased from 56 to 1.5 mD, resulting in rather decreased
oil recovery. For this reason, there should be an optimum concentration for maximizing the oil recovery.
It was also confirmed by shear rate analysis. At high concentration, the shear rate near injection where
has the highest velocity was greater than critical rate. This means that polymer molecules adsorbed to
mono-layer of adsorption by hydraulic force, and the adsorption became additionally thicker and hindered
the oil flow.
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