Rheology of Synthetic Polymers in Porous Media
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This master thesis is written out of the Centre for Integrated Petroleum Research (UNI CIPR) at the University of Bergen (UiB). The aim of this study has been to describe the polymer rheology of the high molecular weight synthetic polymer HPAM 3630S and the lower molecular weight synthetic polymer HPAM 3230S in a linear flow through porous media. The experiments were set up with a pump, two core samples wired in series, two differential pressure gauges, and a backpressure regulator. The idea behind the experiment is to inject low and high molecular weight polymer solutions through both core samples and measure the differential pressures at different injection rates at steady state. With this information it is possible, with help from Darcy's Law and a proportionality formula between injection rate and shear rate, to calculate the apparent viscosity and apparent shear rate of the polymer solution in the porous media. The apparent viscosity could then be compared to other apparent viscosities and rheometer measurements. In the experiments it was found that the rheological behavior of viscoelastic synthetic polymers is different from rheometer measurements. The degree of shear thickening (viscoelasticity) seems to be larger in porous media, a steeper viscosity increase compared to what was expected, especially for the high molecular weight polymer. In the rather short cores used for injections there was also an evident shear thinning region at injection rates lower than the onset of shear thickening. In the rheometer data there was found to be a large deviation in viscous properties for high molecular weight and low molecular weight polymers. The low molecular polymer did not only show less viscosity per ppm solution, but also a less shear thinning and shear thickening effect at concentrations where the viscosity at a shear rate of 10s-1 was nearly identical. The viscous behavior in porous media showed that the low molecular weight polymer showed a later onset of shear thickening, although more viscous at medium to low injection rates than what to be expected from rheometer results. The low molecular weight polymer also showed less permeability reduction and less mechanical degradation of the two.