Drag reduction using high molecular weight polyacrylamides during multiphase flow of oil and water: A parametric study

Five linear, water-soluble, sulfonated polyacrylamides of relatively high molecular weights were used to investigate drag reduction in oil-water multiphase flow through a horizontal, 30.6-mm pipe. The polymers were negatively-charged due to the presence of different density of the acrylamido tert-butyl sulfonic acid, ATBS, side groups along with acrylamide. They have different molecular weights and sulfonation degrees to investigate the effect of these polymer parameters in drag reduction during oil-water multiphase flow. Tap water was used as the aqueous phase and model oil with a density of 0.886 g/cm3 and a viscosity of 18.6 cP at 30 °C was used as the oil phase. The two phases were used in the tests at different oil fractions and mixture velocities to achieve a dispersed flow pattern. The maximum drag reduction was obtained for polymer concentrations higher than 20 ppm in the test section. Drag reduction effectiveness was negatively affected by the increase in oil fraction in the test section leading to negative drag reduction when the oil is initially the continuous phase. Moreover, drag reduction increased with the increase in mixture velocity especially above 1.0 m/s for polymer concentrations higher than 10 ppm. Using this family of polymers, it was concluded that flexibility (or rigidity) of polymer chains in solution is a primary factor in polymer's effectiveness as a drag reducing agent. In this study, drag reduction was higher for more flexible polymer chains, which was enhanced by using higher molecular weight polymers and lower charge density.