Development of models to predict the viscosity of a compressed Nigerian bitumen and rheological property of its emulsions

The viscosity of a compressed Nigerian bitumen was measured over a temperature range of 85 °C to 150 °C. It was found that the viscosity at 85 °C and atmospheric pressure, increased from 1894 mPa s to 2787 mPa s at 7 MPa. At the temperature of 150 °C, the viscosity increased from 65 mPa s (at atmospheric pressure) to 71 mPa s at 7 MPa. Water-in-oil and oil-in-water emulsions were formed in a microreactor. The viscosity of original oil at 60 °C and shear rate of 0.14 s⁻¹ increased from 34,535 mPa s to 46,130, 59,867, and 71,912 mPa s due to the formation of water-in-oil emulsions containing 15%, 35% and 55% w/w water dispersed in the oil phase, respectively. On the other hand, the viscosity at the same condition was found to have decreased to 239.9 mPa s and 1260 mPa s as a result of 55% and 70% w/w oil particle dispersed in the alcoholic-caustic solution containing hydrophilic polymeric surfactant. The flow activation energy E_a decreased with increasing water fraction (increased viscosity) for W/O emulsions and increased with increasing water fraction (decrease in viscosity) for O/W emulsions. Moreover, viscosity prediction models have been developed and verified using the experimental data.