Study On Rheology And Compression Characteristics Of W/O Waxy Crude Oil Emulsion

Waxy crude oil emulsion as a common form in oil-water mixing process,its viscoelasticity and compression properties are of great significance to further understanding the restarting model of oil products and guarantee the safety of multiphase pipeline.Wax crystals will start to precipitate,the storage modulus and loss modulus will increase,the loss angle will decrease when the crude cools to the temperature below the wax precipitation point.At present,the study on the viscoelastic model and the compression characteristics of crude oil and waxy crude oil emulsions have not yet matured,and existing models are not ideal for describing the viscoelastic parameters of waxy crude oil during the cooling process,more importantly,the application of ultrasound in emulsion is mostly used for demulsification.Therefore,the study on the viscoelasticity in the cooling stage and compression properties of crude oil and waxy crude emulsions still need to be further studied.First,this paper tests the emulsion by colorimetric method,microscopic observation,and rheology,compareing the microscopic characteristics and rheological properties of the emulsion under different preparation conditions,making sure the best solution for the emulsion,55 ?C 1500 r.The existing relational expression can't describe the viscoelastic parameters of the waxy crude oil cooling process well.The wax crystal image and viscoelastic parameters were measured at different cooling rates of Shengli crude oil and Sudan crude oil.The results show that when the crude drops to the same temperature,the number and area of wax crystals,the storage modulus and loss modulus decreased with cooling rate increasing.Along with the cooling rate increment,loss angle and gelling temperature reduces.Wax precipitation and gelation of crude oil show “hysteresis”.The 0.4 power of relative storage modulus and relative loss modulus have a significant linear correlation with the cumulative wax precipitation.A new prediction relational expression between storage modulus,loss modulus and cumulative wax precipitation was proposed and parameters of the relational expression were determined by fitting experimental results.The results show that the relational expression can well describe experimental dates and the parameters in the relational expression can be used to characterize the effects of different crude oil properties and cooling rates.Then,this paper studies the law of ultrasonic wave of emulsions at different water contents during different temperatures and constant temperature static and starting process by using ultrasonic device.It found that ultrasonic velocity would increase,when the structure of emulsion is stronger.The ultrasonic velocity of emulsion showed the negative linear correlation with temperature change,and there are two inflection points.The crude oil curve has only one inflection point,and the change trend is the same as that of the emulsion.Using phase volume function method,SFC method,volume method and mass method to calculate the ultrasonic wave of crude oil and emulsion,results show that the volume method is better.The formula for calculating the compressibility of emulsion is derived,and the compressibility of Shengli crude oil emulsions with five water content conditions are verified.The results show that the fitting effect is good.