Study On Static Structure Recovery And Starting Characteristic Of Gelled Crude Oil In Pipeline

In operation of actual pipeline,it's inevitable to cause pipeline shutdown because of planed check or accident maintenance.At low temperature,the research on process of pipeline shutdown and characteristics of structure recovery of waxy crude oil and restart in pipeline is of great importance for the safe and economic operation of petroleum pipeline.On the basis of pipe flow loop experiments,analyze the pressure distribution along loop in process of static structure recovery and restart.The main research contents in this paper include these following aspects:(1)Analyze pressure distribution of condensate oil along the pipeline in the restart process of flow control,redefine the start-up yield stress of condensate oil along the loop,and propose a way to get the pressure distribution expression in the start time by applying polynomial fitting,calculate the start-up yield stress of condensate oil along loop by differentiating the pressure distribution expression in the end of loop.By analyzing pressure versus time at different locations along loop in start-up process,obtain thixotropic data of gelled crude oil in loop at start-up time and after restart.According to the thixotropic data,calculate relative parameters of the thixotropic model.(2)By analyzing pressure versus time at different along the loop in process of static structure recovery under the static pressure,find that the pressure along loop distributes linearly when the pressure along loop is stable,and define equilibrium pressure gradient.Compared with start-up yield stress under different conditions qualitatively,it's proposed that the equilibrium pressure gradient can reflect structural strength of condensate oil in loop.(3)Based on the computational method of start-up yield stress of condensate oil along loop and equilibrium pressure gradient proposed in this paper,calculate start-up yield stress of condensate oil along loop and equilibrium pressure gradient in process of static structure recovery under the static pressure.From the curves of static pressure applied with start-up yield stress of condensate oil along loop and equilibrium pressure gradient,it's concluded that the structural strength of condensate oil along loop first increases and then decreases with the increase of static pressure applied.(4)By analyzing pressure versus time in at different locations along loop in the process of static structure recovery of crude oil under the static pressure,find that the pressure along loop distributes linearly at any time,define pressure gradient,and point out that the change of pressure distribution versus time along loop can reflect the characteristics of static structure recovery of crude oil in pipeline.In contrast with the change of pressure gradient with time along loop,analyze the effect of these factors on characteristics of static structure recovery of crude oil in loop,including pre-shear rate,cooling rate,the test temperature,and hydrostatic pressure applied steadily in process of static structure recovery.