Drag reduction measurements were conducted on extensively characterized poly(ethylene oxide) and poly(acrylamide) utilizing a fully automated rotating disk rheometer equipped with an optical tachometer, torque transducer, and software allowing real-time data acquisition. The instrument sensitivity allowed the study of concentrations as low as 0.1 ppm. In addition, previously immeasurable concentrationand time-dependent shear degradation effects were readily observed. A power law equation was shown to adequately correlate the percentage of drag reduction and the volume fraction for each polymer. Furthermore, an empirical shift factor was utilized to superimpose data from all the systems that were studied. By conducting measurements in the proper concentration and time domains, it was possible to extract the minimal concentration for the maximum drag reduction efficiency in the absence of shear degradation. The resulting values were significantly higher than those previously reported by our laboratories for poly(ethylene oxide) and poly(acrylamide).

ABSTRACT:The extensional viscosity for aqueous solutions of high molecular weight poly(acrylamide) copolymers and poly(ethylene oxide) homopolymers was measured using a laboratory-designed screen extensional rheometer. A Bingham model was developed to estimate the average local polymer coil extensional viscosity ( coil ). A strong correlation was found between the measured coil values and the polymer extensional viscosity predicted by a bead-spring model. The dilute aqueous solution drag reduction was measured with a rotating disk instrument under conditions minimizing the effects of shear degradation. Extensional viscosity and drag reduction measurements were performed in deionized water and in 0.514M sodium chloride. The relative drag reduction efficiency values (⌬) in both solvents were found to strongly correlate with measured coil values. This is the first report of the accurate prediction of drag reduction behavior for a wide range of polymer types in various solvents from the independently measured molecular parameters coil and []C. The often-used relative drag reduction efficiency expressed as the product of []C and ⌬ can now be replaced by the absolute drag reduction efficiency []C coil .

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Extensional flow encountered by polymers used in reservoir flooding for EOR has been studied on a lab scale using flow through a series of 0.5 inch diameter woven mesh nylon screens. Dilute polymer solutions have been used as mobility control agents in EOR because of the high viscosity resulting from solutions undergoing extension. Polymer chemical composition, solvent quality, and molecular weight were found to affect extensional performance. A yield stress was measured for many of the polymers examined in this study indicating that not all polymers undergo extension at the low flow rates typical of EOR. Polymer FloodingAqueous polymer solutions are often used as displacing fluids employed during reservoir flooding. To be economical, the polymers must increase the flow resistance of the displacing fluid at concentrations as low as parts per million. 310