Study On Viscoelastic-Thixotropic Characteristics Of Heavy Crude Oil And Its Emulsion

As the conventional crude oil resources dwindling,the heavy crude oil resource has been paid much attention than before.During the process of oil extraction,it's easy for heavy crude oil to form W/O emulsion when mixed with water.So far the research on the rheological properties of heavy crude oil emulsion is neither enough nor systematic.In this dissertation,the rheological property of the heavy crude oil and its emulsion are studied preliminary.Different from the wax crude oil gel and emulsion gel are Non-newtonian fluid below gelation temperature,heavy crude oil emulsion become Non-newtonian fluid as the increasing of water cut.The research ideas of this dissertation are as follows:First,different preparation conditions were changed to study how the stirring speed has an effect on the emulsifying process and the stability of heavy crude oil emulsion,including stirring speed,mixing time and the amount of emulsifier.It was found that heavy crude oil become more easily to be emulsified,by divide the preparation process into two steps,and the emulsion is more stable at the same time.Firstly mix the water and the oil by lower stirring speed than improve the speed to form the W/O emulsion.Second,through the oscillatory shear experiment in both the constant temperature condition and the cooling temperature process and the creep-recovery test,the influence of dispersed water on rheological properties of heavy crude oil emulsion,and the reasons for the change of viscoelasticity were studied.It was found that the emulsion became more elastic with the increase of water cut and the decrease of temperature,which is the same with wax and its emulsion.While the loss angle of heavy crude oil emulsion shows opposite trend as the decrease of temperature from 50 ? to 10 ? for different emulsions.If the loss angle below 45°,it increases with the decrease of temperature.While if the loss angle above 45 °,it decreases with the decrease of temperature.At last,through the shear-rate stepwise increase test and the hysteresis loop,it was proved that there is no thixotropy for heavy crude oil,and there is only weak thixotropy for heavy crude oil emulsion of high water cut.