| Polymer flooding is the most widely used tertiary oil recovery method.After polymer flooding,the recovery of crude oil is about 50%,which still has great development potential.It is of great significance to enhance the understanding of micro-flooding mechanism of polymer flooding and the distribution of residual oil for tapping potential of residual oil and improving oil recovery.In this paper,a variety of experimental methods,combined with physical experiments and numerical simulation,are used to comprehensively study the micro-flooding mechanism and residual oil distribution of polymer.Firstly,polymer flooding experiments were carried out based on two-dimensional etched glass model,and polymer viscoelasticity was described based on Oldroyd-B constitutive equation.Viscoelastic fluid flooding simulation was carried out on the same model.Secondly,based on CT scanning technology,the polymer micro-displacement experiment was designed to obtain the three-dimensional fluid distribution in the core at different displacement time,reconstruct the digital core,and quantitatively study the distribution state and location of residual oil after polymer flooding,and compare the residual oil distribution after polymer flooding with different permeability cores and displacement velocities.Based on the digital cores obtained by CT scanning experiment,the corresponding pore network model is extracted,and the seepage characteristics of water flooding and polymer flooding are simulated.The remaining oil distribution under different displacement systems is studied,and the influence of pore structure and wettability on polymer flooding results is analyzed.Based on the real irregular pore network model,the seepage characteristics of water flooding and non-Newtonian fluids are simulated,the residual oil distribution under different displacement systems is studied,and the influence of pore structure and wettability on the displacement results of non-Newtonian fluids is analyzed.Two-dimensional etching model study shows that polymer flooding can effectively improve the direction of displacement fluid flow.Cluster,blind end and film residual oil are reduced,and polymer flooding can improve oil recovery by 13.66%in numerical simulation experiments.CT micro-displacement experiment of real core shows that the results of enhanced oil recovery by polymer flooding in different permeability cores are different.When the permeability is 3989×10-3?m2,1543×10-3?m2and 813.6×10-3?m2,the enhanced oil recovery by polymer flooding is 10.13%,6.30%and 4.34%respectively.Under the experimental displacement speed,the enhanced oil recovery effect of polymer flooding becomes better with the increase of displacement speed.The simulation results of polymer flooding pore network show that with the decrease of permeability,the effect of enhancing oil recovery by polymer flooding decreases gradually,and with the increase of water wetting degree,the oil recovery by polymer flooding increases with the change of wetting angle of the model. |
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