A New Treatment Technique of Produced Water from Polymer Flooding

After the water flooding process or secondary oil extraction, the tertiary oil extraction has been widely used in Chinese oilfield in recent years. Although this technology can enhance the oil recovery by up to 12%, it also produces more and more polymer-flooding wastewater as byproduct per year. Without proper treatment, the oil pollutant pollutes and poisons the water and atmospheric environment. Removing polymer and oil from the oilfield produced water is an important aspect of pollution control in oil and gas industry of China. One of the major technical requirements of the crude oil exploitation industry is to minimize the concentration of hydrolyzed polyacrylamide (HPAM), crude oil and suspended solid (SS) in the oilfield polymer-flooding wastewater and realize the reuse of this wastewater. In this study, the membrane technology was used to achieve this goal in laboratory-scale dead-end test unit with flat polyvinylidene fluoride (PVDF) membrane (MW 100 kDa). We systematically inspected the membrane fouling mechanism, the variety of total membrane resistance, total fouling resistance, the dominant resistance, membrane fouling driving force and the filtration proceeds in the filtration process. The orthogonal method and multivariate linear regression method were applied to analyze the influencing degree of the main pollutant concentration on the critical flux. According to comparison of the average rates of change of the critical flux for the HPAM concentration, oil concentration and SS concentration in single solute solution, double solute solution and oilfield polymer-flooding wastewater, HPAM can decrease the average rate of change of the critical flux for other two solutes and has the crucial effect on the critical flux. According to this research, the ultrafiltration membrane technique can be efficiently used to treat synthetic oilfield polymer-flooding wastewater. A standard procedure is developed to be a methodology reference for the wastewater treatment.