Removal mechanism of oil-sticking layer based on surface energy characterization

Waxy crude oil sticking to pipeline walls during low-temperature transportation poses serious flow assurance challenges. This study aims to develop a predictive model for the Wall Sticking Occurrence Temperature (WSOT), defined as the critical point where adhesion shifts from removable to stable. The framework investigates the interfacial adhesion and removal of congealed oil particles from the initial oil-sticking layer. It integrates the extended DLVO (XDLVO) theory with a mechanical equilibrium model to characterize particle-layer interactions. Three removal mechanisms (lift-off, shear-induced sliding, and rolling) are systematically evaluated based on the balance between cohesive and hydrodynamic forces, linking microscale forces to macroscale flow assurance. The results show that cohesive forces increase markedly with decreasing temperature, especially below the pour point, stabilizing adhesion and hinder particle removal. At higher temperatures, sliding and rolling jointly promote detachment, whereas rolling dominates under lower temperatures; lift-off plays only a minor role under transport conditions. Model predictions of WSOT for four crude oils deviated from experimental and field data by less than 2 °C, demonstrating strong predictive accuracy. This study provides a theoretical tool for optimizing temperature control strategies in real-world pipelines, providing potential for reduced energy consumption and lower carbon emissions.