A Unified Model for Aggregation of Asphaltenes

Abstract

Asphaltenes are the heaviest and most polar fraction of crude oil. They can precipitate at any point of oil production or transportation as a result of changes in the temperature, pressure, or composition. Their precipitation and deposition are having a serious economic impact on petroleum production. It was previously shown that that the precipitation of asphaltenes is a kinetic phenomenon. In this work, it is demonstrated that the kinetics of precipitation is universal among many different crude oils. However, the aggregation rates strongly depend upon the properties of the crude oil or the solvent used to stabilize asphaltenes. A new method of analysis is developed to estimate the aggregation rates by accounting for the properties governing the aggregation kinetics using Smoluchowski’s aggregation model. It is shown that the viscosity and solubility parameter of the solution play an important role in controlling the aggregation behavior of asphaltenes in different crude oils and different model oils. However, with certain key assumptions in the kinetic analysis, all disparities in the aggregation rates of asphaltenes for different types of asphaltenes and crude oils disappear and the rates collapse onto a single curve. These findings will lead to a better understanding of the properties that govern the destabilization and growth processes, which can, in turn, give rise to new predictive models to foresee precipitation kinetics under different operational conditions.