Study on the biodegradability of a chitosan‐modified hyperbranched polymer for enhanced oil recovery

Abstract This study introduced a chitosan‐modified hyperbranched polymer (HPDACS). The biological oxygen demand, chemical oxygen demand, and biodegradability of HPDACS under different water quality were measured under static conditions, as well as the concentration changes before and after degradation. Environmental scanning electron microscopy (ESEM) was used to observe the micromorphology before and after degradation. The biodegradability, viscosity change, and molecular weight change of the polymer before and after passing through the porous medium were measured. The results were compared with the partially hydrolyzed polyacrylamide and the dendritic polymer. The results showed that in bacteria‐containing sewage, the biodegradation rate of HPDACS reached 81%. Moreover, the molecular backbone of HPDACS was completely broken after degradation. Its viscosity loss reached 84.87%, indicating its good biodegradability. HPDACS also can reduce the concentration of polymer in the produced fluid. In core flow experiments, viscosity of HPDACS is loss to 40%. The hyperbranched network structure of HPDACS can reduce the shearing action in the porous medium, thus reducing the extent of biodegradation. The presence of microorganisms resulted in a viscosity loss of HPDACS of ~2%. Therefore, HPDACS can fully exert the fluidity control effect through the porous medium and can meet the requirements of polymer flooding.