Abstract: In response to the widespread development of dominant seepage channels, low efficient circulation on invalid circulation in the oil reservoirs after polymer flooding in Daqing placanticline, physical modeling experiments, numerical simulations, and dynamic analysis of typical blocks were used to study the seepage capacity, development of dominant seepage channels and formation mechanism of oil reservoirs after polymer flooding of Daqing placanticline. The results show that: (1) The overall seepage capacity of heterogeneous oil layers decreases after polymer flooding, however, the seepage capacity gap between high and low permeability oil reservoirs further widens, and the relative liquid intake of high permeability layers gradually increases.(2) After polymer flooding, the dominant seepage channels of oil reservoirs in Daqing placanticline are mainly developed at the bottom of PⅠ2 and PⅠ3 units, with an average effective thickness of 3.8 m, accounting for 18.4% of the total well thickness. The average air permeability is 3 775 mD, and the oil saturation is 24.6%. The remaining reserves account for 10.9%, and the relative fluid intake exceeds 60%.(3) The formation mechanism of dominant seepage channels includes: difference in mud content between high and low permeability layers in heterogeneous oil reservoirs after polymer flooding leads to further widening of permeability max-min ratio, and difference of oil saturation and characteristic relative permeability curves of oil reservoirs with high and low permeability leads to a significant increase in water oil mobility ratio.

Key words: oil reservoir after polymer flooding, dominant seepage channel, seepage capacity, relative liquidintake, mud content, oil saturation, relative permeability curve, water oil mobility ratio, Daqing placanticline