Flow of hydrophobically associating polymers through unconsolidated sand pack: Role of extensional rheology and degree of association

Abstract

Theoretically, both the polymer’s resistance to flow and retention are the reasons for the additional pressure drop and resistance factor (RF) generated during polymer flow in porous media. In the case of hydrolyzed polyacrylamide (HPAM), the increase in RF at high flux rates, a phenomenon called shear thickening were successfully correlated in our previous works using the combination of shear and extensional rheology alone. Associative polymers that have gained increased attention for enhanced oil recovery (EOR) applications have relatively a higher retention value in porous media than HPAM. No attempts were made in the literature to investigate whether the associative polymer’s flow behavior at various hydrophobicity in porous media could be correlated using the bulk rheology alone. Further, the role of hydrophobicity and concentration on the associative polymer’s shear thickening and extensional behavior were not studied.In this paper, high flux single phase porous media experiments were performed using three different associative polymers of varying hydrophobicity at 1000 ppm and 2000 ppm concentration in the unconsolidated sand pack. Extensional rheology was performed on these polymers using capillary break-up extensional rheometer. Extensional rheological parameters become lower with increasing hydrophobicity at both 1000 and 2000 ppm. Porous media result indicates that extensional rheology is directly correlated with the RF in associative polymer at 2000 ppm but not at 1000 ppm. At 1000 ppm, the highest RF is exhibited by higher hydrophobic polymer that possess least extensional resistance. Unusually higher retention value observed at 1000 ppm explain the increased RF associated higher hydrophobic polymer or else it could be due to the clustered hydrophobic species formation that appears to be active only if the concentration is not high enough to breakage. It is also our observation that higher retention cannot be predicted through bulk rheological measurements and therefore, this work signifies that a combination of retention and extensional rheological parameters are needed to model the flow behavior of associative polymers in porous media at higher fluxes. Moreover, the relative influence of retention and extensional rheology on the flow behavior of associative polymer is strictly a concentration and hydrophobicity dependent.