A general model for predicting apparent viscosity of crude oil or emulsion in laminar pipeline at high pressures

In this study, the effects of various parameters such as power-law index of fluid (with the value of n 0.3-0.9), flow rate (0.1-2.0 m/s), pipe inner diameter (0.01-0.05 m) and operating pressure (0.1-40 MPa) on apparent viscosity of crude oil and emulsion during vertical pipe flow were investigated based on experimental friction pressure loss data and Hagen-Poiseuille equation. After that a new pressure model for calculating apparent viscosity was proposed. The experimental results obtained in this study showed that the apparent viscosity of crude oils and emulsions are significantly velocity dependent and they decrease when velocity increases. It was also found that the apparent viscosity increases with increasing in operating pressure. The pressure loss data obtained under high pressure in this study was used to develop new apparent viscosity model by modifying the original Metzner-Reed model. When at atmospheric pressure, the comparative evaluation of the new model with the original Metzner-Reed model and Newtonian approximation model indicated significant improvement in friction pressure loss estimation. A high goodness of fitting (R2, 0.9987) can be achieved when used the modified model to calculate friction pressure loss based on Hagen-Poiseuille equation. This value of R2 is significantly higher than the 0.8445 R2 calculated by Metzner-Reed model, as well as 0.3523 R2 calculated by Newtonian approximation model. In addition, the accuracy of newly developed model was tested against four sets of experimental data obtained from literatures. Results of this comparison also showed that friction pressure loss predicted by new modified apparent viscosity model is in better with experimental data compared to those predicted by Metzner-Reed model. Finally, the pressure model was proposed based on the modified model and shows a good agreement with the experimental data.