A Regular Study On The Effect Of Microscopic Characteristics Of Waxed Crude Emulsions On Wax Deposition

In China,high wax crude oil is widely distributed,majority of the oil fields are already in the medium to high water cut period,and most of the wells are mixed oil-water or oil-gas-water.Highly waxed crude oil often forms a water-in-oil emulsion during the oil-water mixing process,complicating the wax separation process and effective prediction of wax deposition.In this paper,the waxy crude oil in PetroChina Huabei Oilfield is taken as the research object.Firstly,the influence of crude oil components on the wax precipitation point is studied by the recombination of crude oil components.Then,the microscopic characteristics and rheology of the crude oil emulsion before and after wax precipitation are studied.A new wax deposition experimental device is built to simulate the wax deposition rate under different deposition conditions.As follows:(1)By constructing simulated crude oil and applying differential scanning calorimetry(DSC)to analyze the effect of four components of crude oil on the waxing point of crude oil,the aromatic content increased from 17.42% to 40%,the waxing point decreased by 7.0?,the peak waxing temperature decreased by 10.0?,and may cause bituminous precipitation;the wax content increased from 19.78% to 40%,the waxing point increased by 4.2?,while the peak waxing temperature increased by 17.6?.(2)The emulsion properties are investigated by preparing different series of water-in-oil emulsions,and the emulsion microstructural characterization parameters were extracted.The results showed that when the water content is 10%?50%,the average particle size distribution of Sauter is 4.01?m?8.65?m.Compared with crude oil,the freezing point of the 50% moisture content emulsion increases by 11.5? and the wax precipitation point increases by 1.38 ?.By introducing activation energy and wax crystallization rate,the relationship between the microscopic characteristics of emulsion and viscosity and yield stress is studied and fitted.The result show that the average fitting errors is 10.11% and 6.91%,respectively;the correlation coefficients of the rheological parameters are all above 0.96.(3)A new dynamic wax deposition experimental device is designed by applying the principle of oil-wax density difference to study the effect of different water cut and temperature difference on the wax deposition parameters.Comprehensive design device basic parameters and experimental data.According to the molecular diffusion mechanism of crude oil wax deposition,the emulsion deposition parameters such as viscosity,shear stress and water content are added to the wax deposition rate model proposed by Burger to derive the crude oil Wax deposition rate model.The model calculation error averaged 13.27%.Finally,combined with the shear dispersion and brownian motion mechanism deposition rate,a comprehensive expression of emulsion wax deposition calculation is obtained.