Performance of Associative Polymers in Porous Media

The propagation of associative HPAM polymers in porous media is greatly dependent on the degree of hydrophobic modification. In this paper, the transport properties of several associative polymers with degree of association from none to high were investigated in Berea cores and silica sand-pack cores. The associative polymer solutions with customary bulk viscosities generated resistance factors that varied significantly, ranging from 10 to over 500. The increasing resistance factors were attributed to the higher level of polymer retention as the degree of association increased. On the other hand, two associative polymers, with a similar degree of association but different molecular weight and bulk viscosities generated similar resistance factors. Hence the effect of molecular weight and bulk viscosity is not as significant as hydrophobic modification in generating in-situ flow resistance. Linear coreflood tests were conducted to evaluate the potential of associative polymer flooding in recovering western Canadian heavy oil with viscosity of 18,700 mPa.s in 3-Darcy sandpacks. The properly selected associative polymer was able to propagate through the sandpack with no significant retention and generate in-situ apparent viscosity twice as high as the unmodified HPAM.