Pore-Level Experimental Investigation of ASP Flooding to Recover Heavy Oil in Fractured Five-Spot Micromodels

Although Alkaline-Surfactant-Polymer (ASP) flooding is proved to be efficient for heavy oil recovery, the displacement mechanisms/efficiency of this process should be discussed further in fractured porous media especially in typical waterflood geometrical configurations such as five-spot injection-production pattern. In this study, several ASP flooding tests were conducted in fractured glass-etched micromodels which were initially saturated with heavy oil. The ASP flooding tests were conducted at constant injection flow rates and different fracture geometrical characteristics were used. The ASP solutions constituted of five polymers, two surfactants and three alkaline types. The results showed that use of synthetic polymers, especially hydrolyzed polyacrylamide, with high molecular weight as well as cationic surfactant increases the ultimate oil recovery. In addition, location of the injection well with respect to the fracture system plays a significant role in the performance of the ASP flooding. For instance, an increase in the angle associated with the longitudinal extension of fractures with respect to the main flow direction resulted in enhanced oil recovery and also postponed the wetting phase breakthrough time. Mechanistic study of this displacement process revealed that dispersive and diffusive behavior of ASP front enhanced the fluid transport from fracture to matrix as well as increased the microscopic displacement efficiency, which both were more pronounced for the case of longer fractures. In addition, emulsification and coalescence mechanisms are responsible for ASP frontal advancement as well as flow of the ASP phase in the invaded portion of the models. Residual oil in the invaded region, which was observed in the form of discontinuous oil ganglia dispersed in the invaded pore bodies or in the form of pendular bridges formed around some of the solid particles, was mobilized in the form of oil wads through the droplets of the displacing phase. In this study, the mechanisms responsible for recovery of the in-situ oil by ASP flooding were mechanistically investigated along with quantitative parametric study on the effect of different fluid/porous media properties on ultimate recovery factor.