Abstract: The gelling processes of waxy crude oil under three different historical conditions were studied in detail. The RS75 rheometer was used in a small amplitude oscillatory shear mode in the study. Meanwhile, the morphology of wax crystals in the waxy crude oil at different cooling rates was investigated through a polarized light microscope. The results show that the gel point of the waxy crude oil becomes lower and the strength of the gel structure reduces with the increase of the cooling rate under quiescent conditions. As the crude oil is kept static under isothermal conditions, with the increase of cooling rate, the recovery rate of the structure increases and the time needed for recovering to balance extends, but the strength of the final balance structure is weaker .At the same cooling rate, the strength of the gel structure for waxy crude oil at a low temperature reduces with the increase of historical shear rate. However,when the historical shear rate exceeds a critical value, the strength of the gel structure keeps nearly unchanged. At the same historical shear rate, the higher the cooling rate is, the smaller the initial storage modulus at low temperature(31 ℃) is and the stronger the strength of final balance structure is.

Key words: Waxy crude oil, Gelling process, Cooling rate, Historical shear rate