Interfacial Rheology Measured with a Spinning Drop Interfacial Rheometer: Particularities in More Realistic Surfactant–Oil–Water Systems Close to Optimum Formulation at HLD_N = 0

Abstract

Three different cases were selected to study the effect of physicochemical formulation on interfacial rheology properties of surfactant-oil-water (SOW) systems by increasing the complexity of the system from a basic case. This was performed by changing the normalized hydrophilic-lipophilic deviation (HLD N ) to attain the optimum formulation at HLD N = 0. Two types of SOW systems were studied: the first one used an ionic surfactant with a salinity scan, and the second one a mixture of two nonionic surfactants in a formulation scan produced by changing their proportion. Both of them contained cyclohexane as a pure oil phase, without alcohol. Sec-butanol was then added as a co-surfactant with hardly any formulation influence on HLD N . The complexity in interfacial rheology was then increased by changing the oil to a light crude with low asphaltene content. The interfacial rheology is also reported for a realistic system with a high asphaltene content comprised of crude oil diluted in cyclohexane with a conventional surfactant and a commercial demulsifier. The findings confirm that at optimum formulation and whatever the scanning variable (salinity, average ethylene oxide number in the nonionic surfactant mixture, or surfactant/demulsifier concentration), the interfacial tension, and interfacial elastic moduli E, E 0 , and E 00 exhibit a deep minimum. These observations are related to the acceleration of the surfactant exchanges between the interface, oil, and water, near the optimum formulation. Several arguments are put forward to explain how these findings could contribute to the decrease in emulsion stability at HLD N = 0.Keywords Crude oil Á Asphaltenes Á Amphiphiles Á Interfacial rheology Á Formulation Á Emulsion stability Á HLD N

The Oscillatory Spinning Drop Technique. An Innovative Method to Measure Dilational Interfacial Rheological Properties of Brine-Crude Oil Systems in the Presence of Asphaltenes

“…In previous reports, we have shown the characteristics of the oscillating spinning drop apparatus [7] and its application in simple [17,18] and more complex systems [20,21]. The contents of the present review start with a short introduction of the basic and practical aspects of the oscillatory spinning drop interfacial rheology technique.…”

“…The selection of the best demulsifier to reach minimum stability requires attaining optimum formulation. Also, studying other factors that cause delay of the drainage of the interfacial film and oppose the deformation of the interface, avoiding drop's coalescence [10,20,21].…”

“…(c) Formulation quality: at optimum formulation where a WIII microemulsion and ultralow interfacial tension are attained, the mass transfer is considerably accelerated [17,23,104]. (d) The presence of cosurfactants: additives such as alcohols (sec-butanol in particular) can increase the rate of mass transfer at the interface [17,21,105,106]. All these phenomena are optimized to attain a high performance of the formulation [25,73,103,107].…”

“…This apparatus can be used to perform interfacial rheology measurements of both low and ultralow interfacial tensions (as low as 10 −4 mN/m). This is critical when the formulation is at or close to optimum [17][18][19], such as in enhanced oil recovery or crude dehydration applications [20,21].…”

“…This is probably due to the formation of non-wetting microemulsion lenses around the droplet [10,19,[48][49][50], which provides a more elastic response to the interface. More performant SOW systems, i.e., higher solubilization, seem to relate to a lower phase angle [19,21]. According to the system's performance, typical values of E at optimum formulation range from 0.01 to 0.1 mN/m.…”