Abstract: The in-situ rheological behavior of HPAM solutions is an important input requirement of reservoir simulation of polymer flooding and governs the performance and economics of the process. The rheological behavior of hy-
drolized partially polyacrylamide(HPAM) solutions in reservoir core samples was investigated at 70℃. Using core-flow tests the effective viscosity of HPAM solutions in core with permeabilities of 0.024 to 1.252(m was de-termined and compared with bulk viscosity of the solutions for a wide range of concentrations(400-1200ppm) and molecular weights(9×1019×10). The effective viscosity of the solutions is composed of the individual con-
tributions of shear viscosity and extensional viscosity. The extensional viscosity was obtained by comparing the shear viscosity measured in rotational viscosimeter with the effective viscosity in cores.The experimental results indicate that shear viscosity governs the flow behavior at low flow rates.However when a critical rate is attained,extensional viscosity becomes dominant. The shear viscosity in core samples can be well predicated by capillary bundle model. The extensional viscosity is a exponential function of the apparent shear rates in cores. The exten-sional viscosity increases with the increasing of molecular weight and concentration of the HPAM solutions,and with the decreasing of permeability of core samples.

Key words: chemical flooding, palymer waterflooding, surfactant waterflooding, fluid flow, rheology, laboratory testing