Abstract: Studies on the relationship between polymer solution rheology and the seepage characteristics in heterogeneous oil reserves provide a useful theoretical basis to improve the efficacy of polymer flooding in offshore oilfields. On the basis of the actual heterogeneity of heavy oil reservoirs in the sandstones of an offshore oilfield, we developed a two-dimensional visual sand-packed model capable of simulating reservoir heterogeneities in the seepage of oil displacement systems within the deeper parts of an oil reservoir, under high pressures. In this work, we performed a rheology experiment using injections with a fixed shear rate on three oil displacement systems. These displacement systems have significantly different rheologies, but similar shear viscosities at the same shear rate. It was shown in this experiment that oil displacement using these three oil displacement systems always resulted in wedge-shaped residual oil distributions within the similitude model. However, there were significant differences between these systems in their transparent areas and seepage patterns. It was shown that polymer solution rheology can delay the onset of ineffective cycling during fluid injections, thus improving the sweep efficiency of oil displacement in low-permeability reservoirs, resulting in increases in sweep efficiency with decreases in the power law exponent, n.

Key words: polymers, viscosity, rheology, heterogeneous, power law exponent, sweep efficiency