Full and Partial Emulsification of Crude Oil–Water Systems as a Function of Shear Intensity, Water Fraction, and Temperature

Abstract

Emulsification of crude oil and water may significantly affect the flow characteristics of the multiphase flow in gathering lines. Obviously, emulsification of a crude oil–water system is greatly affected by conditions such as shear intensity, water fraction, and temperature. However, there has been a lack of quantitative study of the emulsified water fraction of crude oil–water systems under various conditions of water fraction, temperature, and shear intensity. In this work, experiments were conducted by using a stirred vessel calibrated for the determination of mean shear rate, and the emulsified water fractions under flowing conditions were determined by extrapolation of the separated water volume to the moment when stirring was just terminated. Full emulsification of water was observed in a specific range of shear rates and below a critical water fraction, and only partial emulsification might occur above this critical water fraction. The range of shear rates in which full emulsification might occur became larger with a decrease in the water fraction, but it did not change with temperature in the studied range from 40 to 90 °C. For partial emulsification, the emulsified water fraction under flowing conditions was found to correlate well with the entropy production rate of viscous flow or energy dissipation rate regardless of the differences in water fraction, temperature, and shear rate, and a power law equation might well fit the data.

The Use of Biobased Surfactant Obtained by Enzymatic Syntheses for Wax Deposition Inhibition and Drag Reduction in Crude Oil Pipelines

“…There will not be appearances and precipitates of wax crystals above WAT, and the decreased pressure drop in the flow loop can only be attributed to viscosity reduction and turbulent drag reduction. However, as seen in Figure 6, the viscosity reduction rate is about 20%-25% above WAT when drag-reducing surfactant was used, according to the formula of pressure drop [40][41][42]:…”

The Role of Shearing Energy and Interfacial Gibbs Free Energy in the Emulsification Mechanism of Waxy Crude Oil

“…The reason for this is that the water fraction contributes to keeping the droplets in their original shape and distribution when the containing polymer in produced water tries to bound the droplets. When scaling the emulsion structure, for example, the formation of tight emulsions is at the phase inversion temperature [6,46]. This is in agreement with the significant increase of emulsion viscosity which is close to the water cut where dispersed droplets begin coalescing entrapping the continuous phase into dispersed droplets.…”

“…The sellable crude oil must meet a certain specification for transportation and storage on basic sediment and water (BS & W) content. However, the typical BS & W content in a large number of mature oilfields is usually far more than the specification [6]. Before the design of wet crude handling technology and facilities, it is necessary to better understand the formation and stabilization of crude oil emulsions.…”

“…Figure 1 is a schematic illustration showing various agitation points where shearing actions take place during oil production in Daqing oilfield (China). Emulsification of a crude oil-water system is significantly affected by conditions such as water fraction, shear intensity, and temperature [6,7]. As thermodynamically unstable systems, the stability of emulsions is determined by surface forces and intermolecular interactions [8].…”

“…The hydrodynamic interactions of droplet-droplet, droplet-particle, and particle-particle can lead to a more viscous fluid, which will slow the kinetics of coalescence [13,14]. Emulsification of a crude oil-water system is significantly affected by conditions such as water fraction, shear intensity, and temperature [6,7]. As thermodynamically unstable systems, the stability of emulsions is determined by surface forces and intermolecular interactions [8].…”