Synergistic Effects Between Associative Polymer and Different Types of Surfactants on Oil Production: A Visualized Micromodel Study

Abstract

AbstractA visualized micromodel approach was applied at high-salinity condition to investigate the synergistic effect between a polymer and a surfactant in surfactant-polymer (SP) flooding, probe the mechanisms of SP flooding in oil displacement, and establish the most efficient and economic SP flooding strategy. A micromodel setup was used to evaluate oil production efficiency and to investigate the mechanisms of oil displacement with various SP flooding systems. Sequential injections of sea water slug, chemical slug and subsequent sea water slug were conducted after oil saturation. The images captured by digital camera of micromodel equipment were quantified with an image analysis software to calculate the percentage of oil production. The mechanisms of SP flooding were analyzed according to the observed phenomena resulting from SP-induced viscosity enhancement and surfactant-induced emulsification. To the SP flooding solution comprising an associative polymer (AP) and various surfactants, an extraordinary performance of the AP combined with an anionic surfactant (AS) was observed comparing the AP solution containing a non-ionic surfactant (NS) or a cationic surfactant (CS) due to an enhanced sweep efficiency resulting from a high solution viscosity caused by strong interaction (hydrophobic association and electrostatic attraction) between P and AN. Additionally, the AP/AN flooding favored the emulsification of the trapped crude oil to form oil-in-water (O/W) emulsions and micro-emulsions which favored the mobility of the trapped crude oil after water flooding, the emulsified oil droplets subsequently pass through micropores and narrow throats of the micromodel along the flow, resulting a higher efficiency of oil displacement. Therefore, a highest oil production was obtained by the binary AP/AS flooding system among three surfactants. Some phenomena in oil displacement, such as improved volumetric sweep efficiency and emulsified oil in various forms, have been observed via a visualized micromodel test. It has been found that both factors contribute to a higher oil production, as predicted by the capillary number equation.KeywordsSurfactant-polymer floodingOil displacementMicromodelSweep efficiencyInterfacial tension