Influences Mechanism of Chemical Flooding Agent Characteristics on Its Flooding Oil Dynamics

Chemical flooding agents, especially surfactant-based flooding oil agents, have been widely studied due to its excellent emulsification ability. Nevertheless, there are many evaluation methods for chemical flooding agents, and the focus of each test is different. How to combine routine testing with reservoir conditions is an urgent problem to be solved. In this study, different kinds of chemical flooding agents were evaluated by interfacial tension (IFT), minimum emulsification speed, emulsification state, droplet size distribution, viscoelasticity, apparent viscosity in porous media, stability and flooding efficiency. The influence of their characteristics on pressure dynamics during flooding process is analyzed, and the mechanism in different stages of chemical flooding is clarified. It should to comprehensively IFT and minimum emulsification speed to judge the emulsification ability of chemical flooding agent. Apparent viscosity when it flows porous media is more accurate to evaluate the viscosity reducing of chemical flooding agents than traditional viscosity test. Chemical flooding dynamics are mainly divided into three stages: pressure increase (emulsification ability), pressure decrease (fluidity of formed O/W emulsion) and pressure stabilization (flooding efficiency). Emulsification ability of chemical flooding agent determines the speed of pressure increase and the width of main flow channel. O/W emulsion formation, droplet size, and fluidity determine oil flooding/enhanced oil recovery effect. Droplet size, viscoelasticity and stability of O/W emulsion determine the value of maximum pressure and its decrease speed at middle stage. Therefore, the evaluation of chemical flooding agents should mainly consider its emulsification ability and formed O/W emulsion droplet size, viscoelasticity, stability. This study clarified the evaluation focus of chemical flooding, and laid a foundation for the research and development and screening of chemical flooding agent, dynamic analysis of chemical flooding.