Extensional Rheological Measurements of Surfactant-Polymer Mixtures

Polymer solutions flowing in the porous media during enhanced oil recovery (EOR) processes are subjected to both shear and extensional rheological deformation. However, the previous rheological studies conducted on a surfactant-polymer (SP) system or polymer systems were only shear-based. In this paper, the extensional rheological performance of hydrolyzed polyacrylamide (HPAM) in the presence of an anionic surfactant at various concentrations (0, 0.01, 0.05, 0.1, 0.2, and 0.3%) is studied with deionized water and 1% NaCl. Further, the extensional rheological behavior of HPAM in the presence of NaCl and CaCl₂ is studied at varying ionic strengths (1-10%). A capillary break-up extensional rheometer is used for performing extensional rheological characterization. Results revealed that the extensional resistance of HPAM is enhanced in the presence of a surfactant. Particularly, around the critical micelle concentration value of the surfactant (0.1%), HPAM showed higher extensional resistance. Higher extensional resistance for the SP system is observed with deionized water when compared to 1% NaCl. HPAM showed improved performance at 1% NaCl salinity when compared to the higher concentration of NaCl salinity. However, the presence of even 1% of calcium ions is detrimental to the extensional properties of HPAM.