Determining Gelation Temperature of Waxy Crude by Small Amplitude Oscillatory Shear Temperature Sweep Experiment

Viscoelasticity is one of the most important indexes evaluating rhelolgical properties of waxy crude oil. The gelling process of waxy crude is observed with a controlled-stress rheometer RS 150 by small amplitude oscillatory shear temperature sweep experiment, which has the advantage of a continuous evolution of the viscoelastic properties without destroying the crude inner structure. The experimental results show that the gelation temperature at which G'= G", coincides with the gel point when the temperature sweep has a cooling rate of 0. 5-1℃/min. For 14 virgin crudes and 3 PPD-beneficiated crudes with various thermal history, and 96 pairs Daqing crude with different shear history, the gelation temperatures as which G' = G" when the temperature sweep has a cooling rate of 0. 5-1℃/min are in good agreement with gel points. The absolute average deviation between the gelation temperatures and gel points for 113 pairs of compared data is only 0. 5℃, in which the absolute deviation of 110 pairs, that is 97. 3% of the compared pairs, is less than 1℃, the absolute deviation of others 7 pairs is greater than 1℃ but less than 2℃. These results suggest that the gel point of waxy crude can be determined by small amplitude oscillatory shear temperature shear temperature sweep experiment.