An Original SEC Method to Assess Simultaneously Concentration and Hydrolysis of HPAM for EOR

Abstract

Summary An original SEC method to assess simultaneously concentration and hydrolysis of HPAM for EOR. In the current condition of hydrocarbon production, future developments of chemical EOR (cEOR) productions require a specific attention to the monitoring of chemical additives. Polymer flooding or Surfactant Polymer flooding are among the most promising cEOR technologies: the polymer is used to viscosify the injection water in order to get a better mobility control within the reservoir. For those technologies, it would be very beneficial to be able to monitor easily the polymer along the process, from the injection to the back-production. There are different water soluble classes of polymers which are able to increase the viscosity, but the most common polymer used in these technologies is partially hydrolyzed polyacrylamide (HPAM). The most specific and accurate analytical methods to quantify the HPAM polymer content are based on specific amide group dosage. As a consequence, knowing the hydrolysis degree of the polymer chains is an important parameter to determine before doing the quantification. It is also a very important parameter in itself to determine the history of the polymer chains along the process. The amide group hydrolysis can occur in the reservoir, in the wells, in the surface process, depending of physical parameters, as pressure or temperature, and also of the residence time of the polymer. In addition, the hydrolysis rate depends strongly on the water pH of the geological formation. We have developed a new methodology for polymer concentration measurements by size exclusion chromatography coupled to an Ultraviolet (UV) and a Refractive Index (RI) detector. The simultaneous use of these two detectors allows evaluating the hydrolysis rate of the HPAM. As a consequence, it is possible by only one short time analyze to obtain a real HPAM concentration, considering the real amide chemical function remaining in the polymer.