Determination of the Transportation Limits of Heavy Crude Oil Using Three Combined Methods of Heating, Water Blending, and Dilution

Conventional methods for pipeline transportation of heavy or extraheavy crude oils adopt heating, water blending, and dilution, and several methods are generally required to be used simultaneously to ensure normal transportation. However, how to determine the optimal transport boundary conditions for heavy oils is still one of the technical challenges. In this paper, the circulating piping experiment at different water contents (0-90 wt % with an interval of 10 wt %) and temperatures (65-90 °C with an interval of 5 °C) of three heavy oils from the Xinjiang oilfield is carried out. The apparent viscosity calculated from the experimental data of the circulating pipeline shows that when the water content is below the phase inversion point, the apparent viscosity increases and when the water content is close to the phase inversion point, the apparent viscosity increases nearly three times. Only when the water content is greater than the phase inversion point, the apparent viscosity shows a downward trend. Also, then, various viscosity prediction models with different independent variables, which mainly included temperature, water content, and dilution ratio, are selected and verified. Based on experimental data of six crude oils, a prediction model of the phase inversion point is established. Simultaneously, a method for determining the boundary conditions of heavy oils using the combined methods of heating, water blending, and dilution is proposed, while a set of simple decision diagrams of boundary conditions for heavy oil is also described. Finally, verified by the heavy oil pipeline of the Bohai LvDa oilfield, the gathering and transportation limits determined by this method are consistent with the operating parameters of the oilfield.