Potential Study on Enhanced Oil Recovery Potential of Polymer Flooding After High-Speed Water Flooding in Low-Viscosity Sandstone Reservoirs

The use of polymer drive to further increase the recovery in high water-bearing oil fields is a relatively common method for tertiary oil recovery at present. Polymer drive experiments in low viscous sandstone reservoirs show that the increase in recovery after low-speed water drive is 7.9%–10.7%, which is close to the effect of polymer drive in most Chinese oil fields (e.g. Daqing oil field), and the increase in recovery after high-speed water drive is only 3.5%–4.8%. It can be seen that the increase of recovery degree after high speed water drive in low viscosity reservoir is much smaller than the effect after low speed water drive. The increase in recovery after high speed water drive is very limited, and it is mainly contributed by the subsequent water drive. The actual mechanism of polymer drive is not a “polymer drive” mechanism, but a “dissection” mechanism of polymer solution segment plug. At the same time, the degree of recovery only increased by about 1% after increasing the polymer viscosity, indicating that increasing the polymer viscosity has little effect on improving the ripple efficiency. Therefore, for low viscosity sandstone reservoirs after high speed water drive, the potential of recovery enhancement by polymer drive is limited.