Rheological Properties of Water-in-Brazilian Crude Oil Emulsions: Effect of Water Content, Salinity, and pH

Abstract

During the crude oil production, stable water-in-oil (W/O) emulsions are generally found along the pipeline between the reservoir and surface facilities. The main objective of this work is discussing about the influence of the salinity (with NaCl at 0, 50, and 100 g·L–1), pH (2, 6, and 10 values), and water content (variations between 8% and 65%) upon the rheological behavior of water-in-crude oil emulsions. Tests including the rotational and oscillatory rheology for assessment of profiles of viscosity, elastic and viscous modulus for the different cases were performed. Semi-theoretical models and available empirical literature models have been successfully used to fit the rheological data, enabling a better understanding of the interactions between the constituents of the samples at a colloidal level. Results presented here show that the emulsion loss modulus calculated from bulk rheological tests does not respond differently for acid, quasi-isoelectric point and alkaline aqueous phase; this modulus also has a salt content-independent behavior for crude oils with different content of resins and asphaltenes. The presence of electrolyte in the emulsions may decrease the storage modulus, once the concentration of resins and in special asphaltenes were low. For higher content of these molecules, the attractive electrostatic forces are not enough to change the interfacial tension between the macromolecules.

Rheology of Water-in-Crude Oil Emulsions: Influence of Concentration and Temperature

“…A lot of studies have been devoted to the rheological behavior of water-in-crude oil emulsions (see, for example [17][18][19][20][21][22]) to better understand these complex systems [23,24] including the role of surfactants and stabilizers [25] and chemical composition of crude oil [26] and droplet size [27]. Viscous and viscoelastic properties depend on many factors such as the viscosity of the crude oil itself, droplet size and size distribution, mechanical impurities if any, dispersed phase (water) content, pH of the aqueous phase, the temperature etc.…”

Naphthenic Acids: Formation, Role in Emulsion Stability, and Recent Advances in Mass Spectrometry-Based Analytical Methods

“…Mechanisms such as steric hindrance, electrostatic repulsion, and the Gibbs-Marangoni effect may likewise affect emulsions stability [27][28][29][30]. Steric hindrance forms a barrier that prevents coalescence between droplets, thus hindering their approximation.…”

“…Steric hindrance forms a barrier that prevents coalescence between droplets, thus hindering their approximation. is barrier is generally constituted by surfactant molecules adsorbed at the droplet interface [27][28][29][30]. In turn, electrostatic repulsion occurs due to the existence of ionic surfactants at the water-oil interface, responsible for the formation of an electric double layer that causes repulsion and prevents droplet collision and coalescence [31].…”

Effect of NaCl concentration on stability of a polymer–Ag nanocomposite based Pickering emulsion: validation via rheological analysis with varying temperature

“…31,[52][53][54] Factors such as effect of salts, concentration of aqueous phase, and temperature can lead to signicant change in the viscosity of an emulsion. 4,28,35,55 This section presents shear rheological properties of emulsions stabilized by low (15 wt%) and high (25 wt%) compositions of PAHz-Ag NC, and the impact of various ionic strength (1.0-5.0 wt%) on these properties is discussed. Fig.…”

“…In emulsions, the elastic strength of interfacial NP layer usually modies by NaCl concentration resulting it leads to signicant change in viscoelastic properties (G 0 and G 00 ) of emulsion. 35 Horozov et al 10 studied the effect of NaCl on the fumed silica particle stabilized silicone o/w emulsions and found that G 0 rapidly increased at higher ionic strength (>2 mM). G 0 of emulsion was below 100 (Pa) at lower ionic strength (<1 mM) and it increased to 200 Pa at ionic strength (>2 mM).…”