Self-lubricated transport of bitumen froth

Bitumen froth is produced from the oil sands of Athabasca using the Clark's Hot Water Extraction process. When transported in a pipeline, water presen t in the froth is released in regions of high shear, namely at the pipe wal l. This results in a lubricating layer of water that allows bitumen froth p umping at greatly reduced pressures and hence the potential for savings in pumping energy consumption. Experiments establishing the features of the se lf-lubrication phenomenon were carried out in a 25 mm diameter pipeloop at the University of Minnesota, and in a 0.6 m diameter pilot pipeline at Sync rude, Canada. The pressure gradient of lubricated flows in 25 mm, 50 mm and 0.6 m diameter pipes closely follow the empirical law of Blasius for turbu lent pipe flow; the pressure gradient is proportional to the ratio of the 7 /4 th power of the velocity to the 5/4 th power of the pipe diameter, but t he constant of proportionality is about 10 to 20 times larger than that for water alone. We used Reichardt's model for turbulent Couette flow with a f riction velocity based on the shear stress acting on the pipe wall due to t he imposed pressure gradient to predict the effective thickness of the lubr icating layer of water. The agreement with direct measurements is satisfact ory. Mechanisms for self-lubrication are also considered.