Numerical Simulation Of Temperature Field Of Crude Oil Pipeline In Shanshan - Sibao Station

The crude oil in the oil field of our country is high wax content oil, which has bad flowability at normal temperature, so it’s a common practice to raise transport temperature to avoid congelation accident in oil pipelines. The viscosity of waxy crude oil increase rapidly as the oil temperature decreases when waxy crude pipelines shut down, which lead to restarting difficulty, even congealing. Research on the regularity of the temperature drop for shutdown crude oil pipelines, has important guiding significance for determining the safety shutdown time, proposing re-start program, as well as developing a the shutdown maintenance plan.This article takes the pipelines between Shanshan-Sibao oil station, which is a part of Shanshan-Lanzhou Oil Pipeline, as a research subject, and collects and arranges basic physical property parameters such as pipeline geometry parameter, environmental condition parameter and the characteristics of transport media. It establishes the geometric, mathematic and numerical models about temperature drop on the basis of the temperature drop influencing factors analysis for buried transport shutdown crude oil pipelines. Effects on temperature drop of temperature field during normal transportation, temperaturedrop process during transport shutdown, atmosphere temperature, crude oiltemperature, insulation thickness, buried depth anddiametersize ofpipelinesare simulated by thesoftware FLUENT.The modeling analysis on factorsaffectingthe pipeline heat conductionshows that:the allowable shutdown time in summeris longerthan that in winter; the higheroil temperature during transportation shutdown is, the longer required shutdown time is; the shutdown timeis longer with the thicker pipeinsulating layer; shutdown time is longer as the pipelines buried depth and pipediameter increases.Thetemperature drop simulation of pipelines during transportation shutdown shows that:for the running pipelines, high-temperature regions are concentrated in the inside part of the pipelines, and as the radius increases, soil temperature declines and the temperature gradient decreases gradually; the temperature gradient above the pipe centerline is greater than that below the pipe centerline;when natural convection is considered, two swirls are formed in the upper region and near the pipe wall in the shutdown pipelines, and natural convection between these two regions is more obvious than that of other regions; at the beginning of the pipelines shutdown, the convection effect enhance the oil temperature decreasing considerably, and the oil temperature decrease rate leading by both heat convection and natural convection is much greater than that causing by heat convection only; viscosity of crude oil increases gradually and natural convection reduces gradually as the crude oil temperature decreases; temperature decreasing rate of crude oil reaches to the original level as that considering heat convection only after two days, but oil temperature is still lower than that considering heat convection only.