Study On Thermal Hydraulic Coupling Characteristics Of Waxy Crude Oil Pipeline Restarting

The transportation of crude oil is an important link in the process of oil production and processing.The pipe is inseparable in the process of oil production,processing,marketing,etc.In the process of pipeline transportation,natural disasters,pipeline maintenance and oil field blackout will inevitably occur.On the other hand,by the impact of the volume,it may also be forced to intermittent shutdown,so there will be planned shutdown and accident shutdown.Restarting the shutdown smoothly or not will directly affect the safety and cost of pipeline operation.In order to ensure the safe and stable operation of waxy crude oil pipeline,this paper studies the process of shutdown and restart of buried waxy crude oil pipeline.For the safe and economic operation of waxy crude oil pipeline,on the basis of steady state operating conditions of crude oil pipeline,the heat transfer model was established,and the finite element method was used to solve the model,the temperature of the pipeline under different shutdown time was calculated,and the soil temperature field of the buried pipeline in summer and winter was drawn.According to the thermal and hydraulic,oil pipe and the medium out of the pipe coupling characteristics of oil pipeline restarting,considering the impact of oil shrinkage,compressibility and thixotropy on restarting characteristics,based on the continuity equation,momentum conservation equation,energy conservation equation and relevant boundary conditions and initial conditions of the crude oil in the pipeline,the unsteady thermal hydraulic coupling model is established.The shock wave theory and characteristic line method was combined to solve the restarting process.The calculation program of shutdown and restarting was written by Matlab,and then a crude oil pipeline buried in summer and winter were simulated.The variation of the oil flow along the first end of the pipeline and the change of the pressure along the time during the restart process is analyzed.The variation of the oil temperature and flow of the first and end of the pipeline with time and the pressure change at the first end of the pipeline in the restarting process was analyzed.The ultimate bearing capacity of pipeline is the judgment basis to determine the safe shutdown time in summer and winter,which provides a reliable theoretical basis for the safe operation of the pipeline,and then guides the safety operation and management of pipeline.