A Study on Mass Concentration Determination and Property Variations of Produced Polyacrylamide in Polymer Flooding

Abstract Because injected polyacrylamide often quickly breaks through to production wells during polymer flooding, its mass concentration determination is very significant. However, due to the variations of relative molecular mass and degree of hydrolysis of produced polyacrylamide, the conventional determination methods, including viscosimetry and starch-cadmium iodide colorimetry, are no longer suitable for determining its real mass concentration. A new determination method—ultrafiltration concentration film drying—is proposed and developed in this article. By purifying and concentrating produced polyacrylamide solution using an ultrafiltration system and then dehydrating water to a constant weight, this method can determine the mass concentration directly. This method has been evaluated in the laboratory and compared with two conventional determination methods, verifying its adaptability and high accuracy. The produced polyacrylamides from three different polymer flooding blocks have been determined using this new method. The results show that the relative molecular mass of produced polyacrylamide decreased greatly and its degree of hydrolysis increased obviously. The reasons and differences have been also analyzed. These corresponding variations make the results determined by the conventional methods much lower than the actual results, and it is implied that the previous methods need to be improved or replaced.