Research On Injection Capacity And Oil Displacement Of Combination System In Second Type Reservoirs

Polymer/ ASP compound flooding system has been applied in first type layers in Daqing Oilfield and has achieved well economic benefits.With the continuous development of Daqing Oilfield in recent years,the main layer basically entered the high water stage.The rising water content of oil wells has led to the gradual reduction of the economic benefits in the oilfield exploitation process.Therefore,it is imperative to increase the exploitation of the second and third type layers.Compared with the first type layers,the second type are with the characteristics of low permeability,thin thickness and poor connectivity,which makes a poor development effect with the traditional flooding method.Thence,the research on the oil flooding system to get a better development effect is of great significance to improve the oil recovery.In order to study the flow-ability and flooding effect of composite flooding system in the second type reservoir,constant-pressure injection method was used to get the flow–pressure relationship in the polymer solution flooding process,and then got the threshold pressure gradient.Based on the experimental data,the relationship among core permeability,viscosity of the polymer system and the injection pressure under the same stability flow rate was researched.The results show that: there is an approximately linear relationship between the injected pressure gradient and the steady flow rate,furthermore,the lower the core permeability and the higher the viscosity of the system,the greater the starting pressure gradient.The experimental data was study and the flowing chart of flow under different injection pressure gradient was drawn.In order to study the seepage law of ASP compound flooding system and its difference with polymer solution,one-dimensional core seepage law experiment was carried out in this paper,and the seepage regularity of different viscosity ASP compound flooding system in different permeability cores was researched.Research indicates that: the flow characteristic of the ASP system in the core is similar to the polymer which should be credit to the polymer in the ASP system.Because of the competitive adsorption of the ASP system in the core,the adsorption of the polymer solution on the pore surface is reduced,which lead to less seepage resistance and the high flow rate under the same pressure gradient.To study its development effect,the three-tube parallel cores experiment was implemented,and the rules among the flow distribution rate,water content and oil production rate of different displacement stages were obtained.The study results indicate that: the watercontent of polymer flooding is generally higher than that of ASP system,and the decrease of water content decreases with the increase of the permeability contrast.Under the same permeability level,the chemical recovery of the ASP system is higher than that of the polymer,and permeability difference is greater,the lower the chemical recovery under the same system.The results of this study can lay the theoretical foundation for the application of polymer and composite flooding system in the second class,and they are of great significance for the effective development of second type reservoirs.