Interfacial behaviour of crude oil/alkali systems in the presence of partially hydrolysed polyacrylamide

Abstract

An experimental study was conducted to examine the effect of a partially hydrolysed polyacrylamide on dynamic interfacial tension (IFT) of crude oil/alkali systems. The system examined contained David Lloydminster crude oil, sodium carbonate and the polymer Alcoflood 1175L. At sodium carbonate concentrations of 0.2 to 1 mass%, plots of IFT vs. t 1 2 where t is interfacial age, showed a linear relationship. Viscosity measurements indicated that the slope of IFT vs. t − 1 2 is a function of the viscosity of the aqueous phase. These results suggest that the process is controlled by the diffusion of surface active species in the aqueous phase to the interface. At sodium carbonate concentrations less than 0.2 mass%, the IFT did not change with respect to time. Increasing polymer concentration in this alkali concentration range caused a slight drop in IFT. At sodium carbonate concentrations equal to 0.2 mass%, addition of polymer up to 2000 ppm had no significant effect on the minimum IFT. However, the time required to reach a minimum IFT substantially increased with polymer concentration. At sodium carbonate concentrations greater than 0.2 mass%, addition of polymer resulted in lowering of the minimum IFT and long term (2 h) IFT values. Again, the time to reach the minimum IFT significantly increased with polymer concentration. Sodium carbonate further hydrolysed partially hydrolysed polyacrylamide. This hydrolysis caused the apparent viscosity to increase with time, especially at 60°C. Such a change in viscosity should be considered when evaluating the effect of the aqueous phase viscosity on dynamic IFT.