Influence of the emulsion phase composition on the physicochemical characteristics of the interface and its impact on droplet coalescence of crude oil emulsion

Abstract

This research project aims to study the effect of the HLD parameter (Hydrophilic/ Lipophilic Difference), a thermodynamic property associated to the surfactant partitioning between emulsion phases, on the physicochemical properties of the interfacial film and, consequently, the energy barrier that separates the thermodynamic state of isolated droplets from that state after the coalescence of the micro drops in the emulsion bulk. The physicochemical characteristics of interfacial films can affect both the continuous phase inversion point of oil / water emulsions and the type of emulsion formed (oil/ water or water/ oil), as well as system stability. This proposal is a continuation of the research that has been developed in the field of emulsions in our research group in recent years and it is the main focus of the recently established EQUINOR/ FAPESP /UNICAMP Research Center at CEPETRO. The present approach focuses on the understanding of the droplet coalescence phenomenon as a function of the chemical and mechanical characteristics (elasticity and viscosity) of the formed interfacial film. Although most fundamental studies use model oils, usually paraffin-based mineral oils with additives that mimic the chemical function of natural petroleum components, such as asphaltenes and resins (surfactants), these fluids only represents the physical properties of an specific crude. Emulsion properties have a very significant dependence on fluid chemistry. Thus, it is necessary to extend the understanding of emulsions to the real world by studying fluids closest to field conditions by using crude oils. In this work, we will investigate the phenomenon of microscopic droplet coalescence (~ 50 µm) and how the physicochemical characteristics of the molecular dimension interfacial film affect the coalescence process, a molecular study that aims the macroscopic understanding of the coalescence, inversion and phase separation processes of water /oil emulsions. Since the composition and structure of the interfacial film are affected by the chemical composition of both phases (oil and water), the variables to be explored will be: temperature, salinity, pH and viscosity of the oil phase. Different Hydrophilic / Lipophilic Difference (HLD) values will be set by working with these variables. HLD is a thermodynamic parameter based on the relative solubility of surfactant in both phases. A correlation will be established between HLD, interface characteristic and the coalescence time between two drops. Aiming a experimental condition closer to the real system (crude oil), the studies will be performed with a crude diluted with diesel to adjust its viscosity to that of the well. (AU)