The Effect Of Dynamic Wettability Hysteresis On Oil Recovery For Low Permeability Oil Layers

In order to study the effect of dynamic wettability hysteresis on oil recovery for low permeability oil layers, artificial cores and natural cores are processed with different chemicals which are different concentrations in this paper to get different wetting experiment cores. We study the effect of water flooding and surfactant-polymer flooding, and do quantify analysis about the relationship of the wettability and the oil recovery by these experiments.The relations of reasonable displacement rate and permeability is obtained by the theoretical analysis when the water flooding oil recovery is maximal.Totally 14 different wetting experiment cores are prepared by changing the concentration of different chemicals with the homogeneous cylindrical artificial cores for low permeability oil layers.We do the experimental research for the water flooding and surfactant-polymer flooding,and the changing curves are plotted by wetting contact angle with the treatment concentration. The oil recovery of water flooding and surfactant-polymer flooding of the artificial cores and contact angle are founded by the curve.The corresponding contact angle is obtained when the oil recovery is maximal.Totally 12 different wetting experiment cores are prepared at the same time by changing the concentration of different chemicals with the homogeneous cylindrical natural cores for low permeability oil layers. We do the experimental research to obtain the corresponding contact angle when the oil recovery is maximal and compare the effect degree between artificial and the natural core through changing wettability under the same conditions.The effect of changing trends is virtually identical, and the impacton the natural core is larger than the artificial core.In order to explore the reasonable displacement rate of the weakly water-wet cores for low permeability oil layers in the condition of dynamic wettability hysteresis, the core is simplified to be a parallel capillary bundle to establish theory relational expression between the displacement rate, contact angle and permeability through the pressure balance equation. We do the experimental study of water displacing oil of the weakly water-wet cores for low permeability oil layers and obtain the relevant theoretical parameters by the experimental data. We do the appropriate amendments for capillary number based on which Moore and Slobod defined. The results show that: the weakly water-wet cores for low permeability oil layers have the maximal water flooding oil recovery which is 47.67% when contact angle is respectively 79.032°; the reasonable displacement rate and permeability are founded by the second curve . The reasonable displacement rate is 1.4 m/d when the permeability of the core is about 50×10^-3μm².