Impact of temperature on oil-sticking layer growth: a surface energy perspective

The cohesive interaction between the residual oil-sticking layer on the pipe wall and dispersed congealed oil particles plays a pivotal role in the growth of the oil-sticking layer. However, the influence of temperature as a dominant factor in this interaction, particularly from the perspective of surface energy, has been insufficiently explored. In this study, the surface free energy and its components of crude oil before and after phase transition were quantitatively characterized based on surface energy theory. The results indicated that the Lewis acid-base sub-components decreased significantly at lower temperatures, while the non-polar Lifshitz-van der Waals component increased. This shift in surface energy characteristics led to a significant reduction in the cohesive energy between congealed oil particles and intensified their interaction with the residual layer, thereby causing a substantial increase in the mass of oil sticking to the pipe wall under low-temperature conditions. These findings suggested that the pronounced increase in the Lifshitz-van der Waals component and the considerable reduction in the electron donor component were the primary factors contributing to oil-sticking layer growth. This work provides a mechanistic foundation for developing effective mitigation strategies for oil sticking during low-temperature transportation.