Abstract:

: this review article presents a systematic analysis of the nature, formation mechanisms, and characteristics of Complex Structural Entities (CSEs) in the petroleum dispersed system (PDS). Crude oil is considered as a colloidal system in which asphaltenes, resins, and light hydrocarbons form stable supramolecular aggregates that determine its rheological, transport, and phase properties. Special attention is paid to the intermolecular interactions that govern aggregation: π–π stacking, hydrogen bonding, van der Waals forces, and electrostatic stabilization. Theoretical models such as DLVO theory and the Yen–Mullins model are reviewed to describe the stability of aggregates and the energy barriers for coagulation. The effects of temperature, pressure, solvent polarity, and external fields on CSE stability and size are thoroughly analyzed. Experimental techniques used to characterize CSEs are discussed, including Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), and Diffusion-Ordered NMR Spectroscopy (DOSY NMR). Based on the literature, CSE sizes are found to range from 20 to 200 nm, and trends under acoustic, thermal, and chemical stimulation are identified. The findings are of high practical relevance for technologies such as deasphalting, ASP deposit control, transport of heavy oils, and physical stimulation methods (e.g., ultrasound, microwave, shear fields) aimed at Enhanced Oil Recovery (EOR).

Keywords: asphaltenes, resins, petroleum dispersed system, CSE, supramolecular aggregates, DLVO theory, π–π interactions, particle size, aggregation, DLS, AFM, crude oil.