Research On Oil Displacement Mechanism And Numerical Simulation Method Of Nano Polymer Microspheres

Although there are differences between different types of reservoirs in the physical characteristics,after the primary oil recovery process to the state of insufficient natural energy,waterflooding is often used to achieve the purpose of enhancing oil recovery.Affected by reservoir heterogeneity,the extension of water injection time will lead to the invalid circulation of injected water.In order to improve the water channeling phenomenon and achieve further production breakthrough,the production measures have gradually changed from water shutoff and profile control to deep profile control.The key to achieve this transformation is to optimize the profile control system.Among many profile control materials,polymer microspheres have attracted much attention because of its characteristics of easy injection,plugging and mobility,and nano-microspheres have been widely studied because they can enter smaller channels.The academic research on nano microspheres are mainly based on two aspects,one is to clarify the understanding of its action mechanism through indoor experiments,and the other is to predict the stimulation effect by using numerical simulation method under specific reservoir conditions.As far as the research status is concerned,due to the fuzzy understanding of the mechanism of this kind of profile control materials,it is impossible to establish a reasonable profile control and displacement theory,and it is difficult to design appropriate application methods,resulting in uneven field application effects,which hinders its large-scale implementation.In order to solve the problems encountered in the field application,mechanism research and numerical simulation of nanomicrospheres,this thesis breaks through the experimental observation limit of micronano fluidic chip,and establishes an experimental method which is suitable for the characteristics of micronano fluid combined with fluorescence tracing technology to clarify its action mechanism.Relying on the indoor experiment,the macro understanding of its blocking regulation effect is obtained,and the parameters related to the effect of the measures are determined.Based on the experimental results,the commercial numerical simulation software is reasonably used to establish an equivalent simulation method for nano-microspheres.After proving the effectiveness and reliability of this method through various ways,it is used to predict the effect of reservoir scale model and evaluate the adaptability of nano-microspheres profile control and flooding method to different types of reservoirs.Microfluidic experimental phenomena show that nano-microspheres exist in the form of "emulsion aggregates",they migrate to the dominant channel and expand with water to form aggregates,increasing the resistance of original water channeling channels,changing the direction of subsequent fluid injection,which can improve the oil displacement efficiency and sweep efficiency at the same time.The core experimental data show that the adsorption retention of nano microspheres decreases with the increase of core permeability,and the resistance coefficient produced by microsphere retention is not only positively correlated with the retention quantity,but also negatively correlated with the retention time.According to the experimental results,the action process of nanomicrospheres is divided into three processes: expansion,temporary blockage and degradation.The numerical simulation software is used to realize fluid characterization and reaction setting.The correctness of the simulation method is improved by fitting the core experimental data,and the influence of injection parameters on the effect of measures is explored to provide reference for the design of injection scheme.The method is applied to low permeability reservoir and medium and permeability reservoir respectively,and the simulation results show that microspheres can improve oil recovery for both types of reservoirs.