Rheo-microscopy in situ synchronous measurement of shearing thinning behaviors of waxy crude oil

Shear thinning is one of the most significant Non-Newtonian rheological behaviors of waxy crude oil, which is also the macroscopic performance attributing to the microstructural evolution. In this work, Rheo-microscopy synchronous measurement of shearing thinning behaviors is first accomplished. Direct dynamic evolution vision of wax crystals and synchronous rheological data are obtained. Overall dynamics and morphological characteristics of wax crystals show that with the shear rate increasing from 0.5 s−1 to 10 s−1, the number of wax crystals in the field of view decreases by 89%, representing a larger dispersion degree, weaker aggregation and layered arrangement. The average angle decreases by nearly 24°, and the standard deviation of the angle also decreases, implying the wax crystals have greater tendency to orient along the flow field and regular arrangement. The shear also has a slight effect on wax crystals micro-morphology, which is demonstrated by the decrease of fractal dimension. The correlation with viscosity is strongest for the motion behavior and arrangement state of wax crystals(Relational degree is 0.8741) near the abnormal temperature. During the cooling down to the gel temperature, the aggregation becomes the dominant factor influencing the viscosity(Relational degree is 0.8316). And the morphology of wax crystals is always the secondary factor. Furthermore, the individual dynamic response of wax crystals to changes in external shear strength is also quantitatively characterized. The alignment of the trajectories with the flow field, the rotation and tumbling motions, together with the dynamic changes in morphology and structure of wax crystals are also discussed.