Effect of combining different factors on the rheological property of crude oil

In this paper, a high-pressure rheometer (MARS 60) was used to conduct rheological experiments on crude oil under varying parameters, including temperature, static pressure, and methane (CH4) dissolution. Combining the Williams-Landel-Ferry equation (WLF equation), Barus equation, and Kishimoto - Fujita model (F-K model), a new model of combined shift factor was used to quantify the effects of different oil parameters on crude-oil viscosity. The results show that higher temperature, lower static pressure, and lower CH4 dissolution reduce crude-oil viscosity. Static pressure and CH4 dissolution have a more significant effect on viscosity in lower-temperature conditions when compared to higher-temperature conditions. Due to the combined effect of the saturation pressure, there is an optimal condition of CH4 dissolution for reducing the viscosity. The shift factor of CH4 concentration is defined as the ratio of the viscosity of crude oil under saturation pressure of CH4 and static pressure, and the results agree with the F-K model. A new model of the combined shift factor was developed with average deviations of the predicted shift factors for Shengli crude oil and Nanyang crude oil being 3.35% and 2.16%, respectively. Finally, the predicted and tested values are basically in agreement.