Abstract
Determining the rate of asphaltene particle growth is one of the main problems in modeling of asphaltene precipitation and deposition. In this paper, the kinetics of asphaltene aggregation under different precipitant concentrations have been studied. The image processing method was performed on the digital photographs that were taken by a microscope as a function of time to determine the asphaltene aggregation growth mechanisms. The results of image processing by MATLAB software revealed that the growth of asphaltene aggregates is strongly a function of time. Different regions could be recognized during asphaltene particle growth including reaction- and diffusion-limited aggregation followed by reaching the maximum asphaltene aggregate size and start of asphaltene settling and the final equilibrium. Modeling has been carried out to predict the growth of asphaltene particle size based on the fractal theory. General equations have been developed for kinetics of asphaltene aggregation for reaction-limited aggregation and diffusion-limited aggregation. The maximum size of asphaltene aggregates and settling time were modeled by using force balance, acting on asphaltene particles. Results of modeling show a good agreement between laboratory measurements and model calculations.
Highlights
Asphaltenes are complex fractions in petroleum fluids, with variations of molecular weight, structures and polarity (Speight 2014)
Kinetics of asphaltene deposition regarding asphaltene aggregation growth is very important to illustrate the state of asphaltene particles
Different mechanisms and behavior can be recognized by the study of asphaltene aggregate size including reaction-limited aggregation (RLA), diffusionlimited aggregation (DLA) and asphaltene settling
Summary
Asphaltenes are complex fractions in petroleum fluids, with variations of molecular weight, structures and polarity (Speight 2014). Asphaltenes are polyaromatic structures or molecules that contain heteroatoms such as oxygen, sulfur and nitrogen and metal elements including Ni and V, which are in an aggregation state in petroleum (Civan 2015). Asphaltenes may precipitate in reservoirs, near the Edited by Yan-Hua Sun. Petroleum Science (2020) 17:457–466 mechanisms of aggregation, it is vital to study the asphaltene aggregation behavior in order to find an effective solution to prevent or mitigate the severity of asphaltene problems. Numerous studies have been carried out to investigate the kinetics of colloidal aggregation of different solid particles (Schaefer et al 1984; Weitz and Oliveria 1984; Sheu et al 1992; Mozaffarian et al 1997; Sun et al 2017; Maqbool et al 2011; Haji-Akbari et al 2015; Mohammadi et al 2016)
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