Investigation on the Safety Temperature Boundary After the Shutdown of Cold Transport Pipelines: Based on the XDLVO Theory and Force Balance

Abstract During the period when the cold transportation pipeline is stopped, the gelled crude oil in the pipeline is prone to adhere and accumulate at the inclined pipe section, adversely impacting operational efficiency. Based on the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory and force balance, this article conducts a study on the safety boundary of cold transportation pipelines after shutdown during the period of extremely high water content. The results indicated that the total interaction of gelatinous oil increased with the drop of temperature at low temperatures. The gelatinous oil particles adhering to the wall surface were subjected to the combined action of adhesion force (Fa), net buoyancy (Fg), and yield force (Fy). Moreover, under low-temperature conditions, four kinds of gelled oil particles all displayed a propensity for adhering to the wall. With the increase of temperature, the adhesion state, adhesion-slip state, and flow-slip state of gelatinous oil particles appeared successively on the wall surface. Subsequently, we developed a predictive model for the minimum adhesion-slip temperature of gelled oil particles, achieving an accuracy within 2 °C. The study is of great significance for determining the safety boundary of cold transport pipeline when it is shutdown.