Research On The Rheology And Wax Precipitation Characteristics Of Waxy Crude Oil Emulsion In Bohai Oilfield

Bohai oilfield is the largest offshore oilfield in China and its production of waxy crude oil is increasing annually.It is extremely easy to form crude oil emulsion in the processes of production,transportation and storage of waxy crude oil,especially in the wellbore and subsea pipelines.under the external forces,water and crude oil commingle accompanied by violent stirring,which leads to production of crude oil emulsion.Compared with waxy crude oil,these changed behaviors give rise to great impact in the processes of oil production and transportation.Therefore study into the flowing and wax precipitation behavior of emulsion is of great significance to enhance oil recovery,optimize oil pipeline design and transportation of crude oil.The paper selects the representative waxy crude oil samples in Bohai oilfield and formulate crude oil emulsion of different watercut.The experiments take a variety of factors to study the flowing and wax precipitation characteristic of crude oil emulsion.The MARSⅢ and DSC are used to study the relationship of watercut,shear rate and temperature with emulsion viscosity and yield stress,discuss the influence of watercut and pressure to wax precipitation point and wax precipitation peak temperature.The freezing equipment is also employed to explore the influence of watercut and shear rate to the freezing point of emulsion.The experimental results show that the viscosity of emulsion increases exponentially as the watercut increases,the rising temperature and shear rate reduce the viscocity and the yield stress increases dramatically with the rising watercut,it also goes up exponentially as the temperature decreases.The emulsion transfers from Newtonian to non-Newtonian fluid as the temperature drops and the higher the watercut the more obvious the non-Newtonian property it shows.The waxy precipitation point increases as watercut rises.Besides,pressure has little impact to the precipitation point which can be neglected.The viscosity data are applied to process and modify the previous model,then the emulsion viscosity model of Bohai crude is obtained.The predicted value which is quite close to the actual one has very high accuracy.it can be used in the fieldwork.