Development of New Perikinetic Collision Frequency Model Using Lifshitz Theory and Surface Energy Approach for Asphaltene Precipitation.

Precipitation and aggregation of asphaltene during production, processing, and transportation are primarily driven by collisions between asphaltene particles. These collisions result from Brownian motion, fluid flow-induced velocity gradients, or external forces such as gravity. The collision frequency, a critical factor in precipitation, is influenced by perikinetic (Brownian motion) and orthokinetic (shear-induced) parameters. Previous studies assumed collision frequency to be constant or dependent on limited variables such as temperature, viscosity, and particle size. In this study, a new perikinetic collision frequency model is developed using Lifshitz theory and a surface energy approach to analyze asphaltene precipitation in crude oil. The proposed model provides deeper insights into the aggregation behavior of asphaltene particles. It is demonstrated that collision frequency is not constant but depends on crude oil and asphaltene structural properties, including the Hamaker constant (refractive index, dielectric constant), fractal dimension, oil viscosity, particle size, separation length, and Lifshitz-van der Waals (LW) and acid-base (AB) interaction energies. Additionally, polarity and aromaticity of asphaltene would profoundly influence the collision rate. The AB component of collision frequency is found to be several orders of magnitude greater than the LW component, highlighting its dominant role in asphaltene precipitation. The selection of optimal collision parameters is crucial for accurately predicting particle size distribution.