Mobility control capability of a modified chitosan hyperbranched polymer in porous media

Abstract

The residual resistance factor (RRF) is an important parameter expressing the mobility control capability of the polymer, and it is related to the polymer molecular structure. This study investigated the ability of three polymers with different molecular structures to establish RRF in a one‐dimensional sand pack model at different permeabilities. In addition, the static adsorption capacity of the three polymers on the rock surface was investigated, and the mechanism of the polymer retention in porous media was explored by changing the wettability of the rock surface. Furthermore, the microscopic morphological changes of the polymers before and after passing through the porous media were observed by environmental scanning electron microscopy. Finally, nuclear magnetic resonance core flooding experiments were used to investigate the oil displacement characteristics of the three polymers in the core. T Results show that the ability of the three polymers to establish RRF gradually decreases with the increase in permeability. Still, the modified chitosan hyperbranched polymer (HPDACS) has the best ability to establish RRF in porous media with the largest static adsorption equilibrium amount of 1249 μg/g. Mechanical capture is the dominant mechanism for HPDACS to establish retention in porous media. In addition, HPDACS has a better ability to enhance recovery. It can improve oil recovery by 20.43%, which is higher than that by dendritic polymer HPDA at 16.34% and partially hydrolyzed polyacrylamide at 10.07%. HPDACS can establish a larger resistance in the macropores of the core. Thus, the remaining oil is better driven in the medium and small pores. This finding indicates that HPDACS has excellent potential for oil displacement.