Study On Viscoelastic Characteristics Of Mixed Waxy Crude Oil

In the process of crude oil pipeline transportation,it is inevitable to encounter shutdown conditions,in the subsequent restart process,in order to ensure the smooth start of the pipeline,the pressure in the pipe must reach the minimum pressure required to destroy the crude oil structure,the size of this pressure is closely related to the viscoelastic characteristics of crude oil.According to the actual situation of qingji mixed crude oil transported by a new thermal insulation crude oil pipeline in northeast China pipeline network,the viscoelastic properties of mixed crude oil were tested by DHR rheometer.The variation trend of microscopic characteristic parameters with temperature was analyzed by means of microimaging system.Finally,the quantitative relationship between the microscopic characteristics and the macroscopic rheological properties of wax-bearing crude oil is established according to the characteristics of the wax-containing crude oil with many factors and complex relations.The research results are as follows:(1)The physical properties of crude oil were measured by a multifunctional low-temperature tester,DSC differential scanning calorimeter and DHR rotational rheometer.It includes basic physical properties,thermodynamic parameters and rheological properties of crude oil.Igawa auspicious mixed crude oil solidifying point is obtained by measurement of31°C,pour point is 34°C,the density of crude oil to 45°C to 35°C is 851-848kg/m~3,respectively related point temperature of 44.38°C,wax content is25.76%,the viscosity-temperature curve,the rheology curve drawing,through small amplitude oscillation test,the sample temperature scanning scanning,scanning frequency,time,etc.(2)The variation law of crude oil storage modulus with different sediment contents with temperature under the condition of small amplitude oscillation was studied,and it was found that with the increase of sediment contents,the gelation temperature of crude oil increased and the structural stability enhanced.An empirical formula describing the change of modulus of gelled crude oil with time under the condition of small amplitude oscillation shearing is presented.(3)The microimaging system was used to carry out a detailed study of crude oil under different sediments,and the relationship between wax evolution area,box dimension and aspect ratio and temperature was analyzed.The effects of different cooling rates on the microcosmic parameters were compared.Finally,the quantitative relationship between the microscopic characteristics and macroscopic rheological properties of waxy crude oil is established...