| China's heavy oil reserves at sea are rich,but the current level of use and has been put into development of heavy oil recovery are low.Polymer flooding is an important strategic means to improve the recovery of heavy oil reservoirs at sea,and its application potential is huge.For a long time,In the field of petroleum engineering,it is generally believed that the mechanism of polymer flooding to improve oil recovery is to improve the ratio of flow and improve the efficiency of macro-wave,but the micro-displacement of polymer solution in porous media is less studied,Especially under the condition of the reservoir temperature on polymer flooding of heavy oil micro understanding insufficiency.Therefore,it is necessary to carry out the study of microscopic wave propagation of heavy oil polymer flooding.Based on the analysis of the pore throat characteristics of heavy oil reservoirs,a two-dimensional glass simulation model with certain geometrical shape was fabricated by photolithography technology.The micro-visualization flow experiment of water flooding/polymer flooding was carried out.Using the collected image analysis The effects of heterogeneity,time of injection,the concentration of polymer solution and the injection rate on the microwaves of polymerized heavy oil were verified,and the reliability of microcosmic model was also verified.On the basis of the experiment,the mathematical model of microscopic flooding was established.Based on the simulation results and the experimental phenomena,the reliability of the mathematical model was explained.On this basis,the effect of microscopic pore throat structure on the microcosmic wave of polymer flood was explored.The phenomenon of water flooding leading edge of the heterogeneous model is more obvious,the breakthrough time is ahead,and the horizontal wave velocity is obviously slowed down after the water flooding channel is formed.After the water flooding,a large amount of network-like residual oil is formed.Polymer injection after water flooding can effectively decrease the longitudinal velocity,lateral spread further to increase sweep efficiency.The residual oil in the heterogeneous model is 38%,and the residual oil is 36%,and the difference is not significant.The homogeneity model accounts for more than half of the network after the polymer flooding.Show stronger heterogeneity,remaining oil distribution after polymer flooding increasingly dispersed,complex and diverse.The results showed that the concentration of water was the highest,which was 85.69%,and the concentration of water was the highest,which was 60.4%.The waterfall was short and wide,The number of oil is less,the distribution is more dispersed.As the concentration of the polymer solution increases,the transverse flow path increases gradually,and the aspect ratio decreases gradually and tends to a smaller value.From the larger scale,the displacement front tends to be stable.As a result,both efficiency and recovery are greatly improved.Polymer into the large pores,with the increase in the speed of displacement,small pores are gradually filled with polymer,expressed as the first increase after the wave coefficient tends to be stable.With the increase of the ratio of pore and throat,the multiplication coefficient decreases,and with the increase of coordination number,the formation of residual oil is reduced and the distribution is more dispersed.Therefore,through the micro-visualization oil displacement experiment,combined with numerical simulation means,for multi-angle,deep understanding of polymer microwaves and provide an effective method,but also to further improve the polymer flooding oil reservoir to provide a certain efficiency Theoretical reference and practical value. |
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