Cationic/Nonionic Mixed Surfactants as Enhanced Oil Recovery Fluids: Influence of Mixed Micellization and Polymer Association on Interfacial, Rheological, and Rock-Wetting Characteristics

摘要

In this study, the efficacy of ioniconionic mixed surfactant systems as a promising chemical route toward enhanced oil recovery applications is investigated. The critical micelle concentration of the (CTAB + Tween 60) surfactant system was confirmed using conductivity studies and surface tensiometry. Thermodynamic analyses revealed that both adsorption and micellization processes in mixed surfactant compositions are more pronounced/effective as compared to pure surfactant solutions. Addition of polymer resulted in improved micellar stability in mixed surfactant systems by steric interactions. Ultralow interfacial tension values were obtained for mixed surfactant systems using a spinning drop technique. In the presence of carboxymethylcellulose (polymer), the viscosity of surfactant slugs are improved, leading to sweep efficiency during oil displacement process. Viscoelasticity investigations reveal that elastic modulus (G') dominate over viscous modulus (G '') at an angular frequency of 1 rad/s, showing their capability to displace trapped oil through low permeability regions. Mixed surfactant solutions exhibit favorable sessile drop spreading onto oil-saturated rock surfaces and alter wetting characteristics to the water-wet state. Surfactant adsorption onto sand reduced significantly in mixed surfactant systems. Flooding studies revealed that nearly 20% of the original oil in place was recovered by (mixed surfactant/polymer) chemical fluid injection after a conventional secondary recovery process. In summary, mixed surfactant + polymer fluids constitute an effective driving fluid for the extraction of crude oil previously trapped within mature petroleum reservoirs.