Mechanism Research On Enhancing Oil Recovery Of Alkali/Surfactant/Polymer Compound Solution With Amphoteric Surfactant

The alkali/surfactant/polymer (ASP) flooding is generally considered as a new technology in Enhanced Oil Recovery (EOR) that can both increasing sweep efficiency and improving displacement efficiency, and that it is regarded as an important technology and has entered into industrial application stages. The implementation effect of ASP flooding depends on multiple factors, including geological feature of the reservoir and interfacial tension between oil and water and wettability as well as fluids loss caused by adsorption and detention, etc. Among them, interface behaviour is an important factor,interfacial tension can influence displacement efficiency of chemical flooding. When there is surfactant in the multisystem, complex can be created through the interaction of polymer and surfactant, many properties of complex are better than that in polymer or surfactant; the synergistic effect of polymer and surfactant can make the system obtaining ultra low inerfacial tension and reduce the loss of surfactant. But, little research has been done about the displacement mechanism of ASP compound system with ampholytics. In this thesis, the experimental study of ASP compound system with ampholytics was progressed, displacement mechanism is discussed.The following works were finished:Firstly, the rheological property and interfacial tension character of ASP Compound system with ampholytics is studied, and the impact of the compound system component changing on the interfacial tension between ASP compound system and crude oil of Daqing oilfield is analysed. The results of investigation indicate that the interfacial tension of ASP Compound system with ampholytics has a lowest point when the compound system component is in a limit field. Different mass concentration of sodium carbonate can caused the different changing tendency of interfacial tension. The impact of sodium hydroxide on interfacial tension is different to that caused by sodium carbonate.Secondly, the displacement oil experiments in artificial and natural core were finished. The displacement characteristics of ASP Compound system with ampholytics after water-flooding and that after polymer flooding were analyzed under the ultralow interfacial tension condition. The probability of enhancing oil recovery is studied by ASP Compound system with ampholytics after polymer flooding. The results of investigation indicate that the recovery ratio can be enhanced further by ASP Compound system under the ultralow interfacial tension condition. The increment of recovery ratio after water flooding and that after polymer flooding are both enhanced with the mass concentration of polymer increasing.Finally, the displacement oil experiments of microscopic simulation model were progressed, the seepage flow process of ASP Compound system with ampholytics at different interfacial tension and the distribution of remaining oil are analyzed after polymer flooding. The probability of enhancing oil recovery is verified by ASP Compound system with ampholytics after polymer flooding. The results of investigation indicate that the advancing value of oil recovery and final oil recovery are both enhanced with the interfacial tension decrease and viscoelasticity raisie of ASP Compound system with ampholytics.