Exploration of the Emulsification Behavior and Mechanism of Surfactants Flooding

ABSTRACT Emulsification is a crucial mechanism in chemical flooding for significantly enhancing oil recovery. This study utilizes a quantitative emulsification index (EI) to characterize oil–water emulsification capacity and employs molecular dynamics simulations to elucidate the underlying molecular mechanisms. The objective is to provide a theoretical basis for screening and designing high‐performance surfactants, particularly for low‐permeability reservoirs where enhancing emulsification is often more effective than solely pursuing ultra‐low interfacial tension after water flooding. Experimental results from an emulsification characteristics analyzer demonstrate that sodium dodecylbenzene sulfonate SDBS (EI = 1.162) possesses a markedly stronger emulsification capacity compared to sodium dodecyl sulfate SDS (EI = 0.32). Molecular dynamics simulations reveal that the benzene ring in the SDBS molecule enhances its overall hydrophobicity, facilitating faster migration and more effective adsorption at the oil–water interface. This leads to the formation of a more compact and stable interfacial monolayer, which provides superior steric hindrance to inhibit droplet coalescence. Conversely, SDS molecules migrate slower and form a looser interfacial layer that relies primarily on electrostatic repulsion for stabilization, resulting in comparatively inferior emulsification performance. This research offers valuable theoretical insights for the screening and molecular design of surfactants aimed at chemical enhanced oil recovery in challenging low‐permeability reservoirs.