Power-Law Flow And Hydrodynamic Behaviour Of Biopolymer Solutions In Porous Media

Abstract

ABSTRACT Aqueous biopolymer solutions have been investigated for their flow behaviour in porous media. A flow equation for these power-law fluids has been derived taking into account the effect of tortuosity on both shear stress and shear rate. A comparison has been made with previous equations (Christopher et al, Bird et al). The equation was applied in flow experiments in Bentheim sandstone rock. Approximately the same flow behaviour exponent n was observed in core flow as in measurements with a rotation viscometer. It was found, however, that the flow coefficient K in core flow is about a factor of 2 lower than observed in a viscometer. This observation is given a plausible theoretical explanation on the basis of a model of a porous medium, consisting of a system of dilatations and constrictions. In the derivation of flow equations it is usually presumed that the diameter of the dissolved particles in the flowing medium is negligible compared to the diameter of the flow channels. This presumption is not valid for polymer solutions. Consequently, the velocity profile of the polymer particles differs from that of the associated brine molecules, so the polymer tends to lead the brine. This hydrodynamic phenomenon provides a more satisfactory explanation for the so-called inaccessible pore volume effect than the concept that water flooding polymers do not occupy all of the connected pores. This has been illustrated in core flooding experiments in the absence and presence of oil. It also complicates the determination of adsorption/retention characteristics of polymer on rock in dynamic experiments.