Abstract
The main objective of this work is to synthesize and evaluate magnetite (Fe3O4) nanoparticle-based ferrofluids for reducing the viscosity of an extra heavy crude oil. The carrier fluid of the nanoparticles was synthesized using an engine lubricant recycled from the automotive industry and hexadecyltrimethylammonium bromide as a surfactant. Fe3O4 nanoparticles were synthesized by coprecipitation method. The effect of the concentration of nanoparticles in the viscosity reduction degree was determined for dosages between 0 and 50,000 mg/L. Different dosages of carrier fluid were evaluated between 0 and 10% v/v. The effects of the amount of brine emulsified, temperature, time, and shear rate were assessed. Overall, the results showed that viscosity and shear stress of extra heavy crude oil could be reduced up to 81 and 78% in the presence of ferrofluid, respectively. The rheological behavior of extra heavy crude oil in the presence and absence of ferrofluid was assessed by Cross, Ostwald-de Waele, and Herschel-Bulkley models.
Highlights
The results of the evaluation of the asphaltene–nanoparticle interaction as well as viscosity and rheology tests for EHO evaluated in the presence and absence of nanoparticles, ferrofluid, and water emulsified are presented
This affirmation is corroborated by the DLS measurements, where it was observed that after h when the system can be considered at equilibrium (Nassar et al, 2015), the mean aggregate size of asphaltenes change from 1017 Æ nm for the system in the absence of nanoparticles to 601 Æ 25 nm after nanoparticles inclusion
Results are in agreement with those reported by Betancur et al (2016) and Nassar et al (2015), who studied the effect of nanoparticles in the kinetics of asphaltene aggregation/fragmentation and found that the mean particle size of asphaltene decreased drastically in the presence of the evaluated materials
Summary
Among the different compounds of crude oil, asphaltenes are usually most responsible for the high viscosities in HO and EHO. Asphaltenes can be defined as the most polar fraction of crude oil that are insoluble in alkanes (such as n-C5, n-C6, and n-C7) and soluble in aromatics (such as toluene, benzene, and xylene) (Adams, 2014; Luo and Gu, 2005; Mullins et al, 2012). The location of the heteroatoms such as O, S, N inside asphaltene molecule grants a highly polar characteristic that provides self-associative properties (Franco et al, 2015a), which lead to the formation of large aggregates whose average size increases as asphaltene concentration increases to form a viscoelastic network and dramatically increase the viscosity (Akbarzadeh et al, 2007)
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