Research On The Formation And Deformation Properties Of Waxy Crude Gel Structure

The formation and deformation of gel structure of waxy crude oil were studied in detail in this work. based on rheology, by applying theology measurement technology, thermal analysis techonlogy (DSC) and optical microscopy measurement technology.The relationship between wax precipitation volume and temperature of Qinghai crude oil during cooling process was measured by DSC thermal analysis. The morphological changes of waxy crystal—at different temperatures as well as those under isothermal process after different pre-shearing rates in static and dynamic cooling processes—was also observed by a polarizing microscope.After studying the formation properties of waxy crude gel structure during static cooling and stress-shear cooling, it is known that the gel structure is much weaker when sheared during cooling, and the bigger the shear stress is, the more difficult the structure can be formed; during static cooling process, less but bigger wax crystals appear when the cooling rate is smaller, thus lead to a stronger gel structure.The structure formation properties during isothermal process after suffering various histories were analyzed by both experimental data and correlation coefficient of the fitting curves. It shows that:for the waxy oil suffering isothermal shearing,when the temperature,pre-shear rate and pre-shear time vary,the changing rate of structure parameter(dλ/dt) and the final structure strength are different;for the oil undergoing dynamic cooling,the cooling rates and the shear rates during cooling process also have a significant impact on the changing rate of structure parameter and the structure strength;for the oil sufferring high speed shearing, a worst shear temperature exists at which when it is sheared,the oil has the most powerful structure at a lower temperature.The deformation properties of waxy crude gel structure undergoing mechanical and heating process were studied detailedly.The mechanical deformation stages were verified by "increase of stress/recovery'test,the formation possibilities of gel structures obtained under static and dynamic cooling were contrasted.The heat-up solation properties of gel structure was researched,it shows that:whether the curve shapes of the G',G",δ-T or the key temperature points were different between the cooling process and the heating process;the smaller the heating rate is,the quicker the gelled oil solates;the higher the start temperature is and the longer the holding time is,the sharper the modului change. The deformation properties during mechanical process afer slight heating was studied by using small amplitude oscillatory shear experiments,it is known that the longer the holding time is and the lower the initial temperature is,the wider the linear viscoelastic scale is after the oil re-gels at a higher tmeperature,and the gel structure is much weaker, a samller strain or stress is needed to cause the yielding of the oil.