Objective Aiming at serious problems of the water channeling at ultra-high water cut stage and the limited mobility control ability of polymer flooding, the micro-flow behaviors of heterogeneous flooding were explored.

Methods The water channeling and the adjustment behavior of polymer flooding on water injection profile at ultra-high water cut stage were evaluated through the microscopic visualization displacement experiment, displacement experiment in the homogeneous porous model, and profile control and displacement experiment in the heterogeneous porous model.

Results The displacement resistance was effectively improved after the injection of polymer and heterogeneous system at the ultra-high water cut stage. The ultimate oil recovery increased by 32.8 percentage points than that of water flooding. The residual oil in low permeability core after polymer flooding can continue to be used by injecting heterogeneous system. The ultimate oil recovery of low permeability sand pack increased significantly 38.1 percentage points than that of water flooding. The heterogeneous system effectively displaced all kinds of microscopic residual oil, and their content decreased significantly.

Conclusion The heterogeneous system can effectively plug the channeling channel, improve the micro-heterogeneity of the porous media, promote the displacement fluid to turn and enter the unswept area, and effectively utilize the remaining oil, thereby improving the oil recovery.