Bitumen froth is produced from the oil sands of Athabasca using the Clark's Hot
Water Extraction process. When transported in a pipeline, water present in the froth is
released in regions of high shear, namely at the pipe wall. This results in a lubricating
layer of water that allows bitumen froth pumping at greatly reduced pressures
and hence the potential for savings in pumping energy consumption. Experiments
establishing the features of the self-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 Syncrude, 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 turbulent pipe flow; the pressure gradient is proportional to the ratio of the 7/4th
power of the velocity to the 5/4th power of the pipe diameter, but the 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 friction velocity based on the
shear stress acting on the pipe wall due to the imposed pressure gradient to predict
the effective thickness of the lubricating layer of water. The agreement with direct
measurements is satisfactory. Mechanisms for self-lubrication are also considered.