The effect of microstructure on performance of associative polymer: In solution and porous media

Hydrophobically associating polyacrylamide (HAPAM) is considered as a promising candidate of polymer flooding because of its excellent apparent viscosifying capability. However, the effective viscosity and the oil displacement efficiency of HAPAM are lower than those of conventional polymers at a concentration of 2000 mg/l. Therefore, the microstructures of two types of polymers were investigated by scanning electron microscopy (SEM) to reveal the relationship between the morphology and properties. The specimens were prepared by accelerated freeze-drying in order to keep polymers with their original morphology without distortion. In aqueous solution, associative polymer exhibited a compact three-dimensional network structure, while only loose network structure was found in conventional polymer. A number of filaments are attached to the associative polymer skeletons when the polymer concentration is higher than the critical association concentration (CAC). But in the porous media, most of the networks of conventional polymer were larger and more integrated than those of associative polymer. It may be interpreted by absorption loss of HAPAM and spatial confinement in porous medium.