Main Controlling Factors Affecting the Viscosity of Polymer Solution due to the Influence of Polymerized Cations in High-Salt Oilfield Wastewater

Abstract

In view of the high salinity characteristics of reinjection oilfield wastewater in the Gasi Block of Qinghai Oilfield, with the polymer produced by Shandong Baomo as the research target, we systematically investigated the variations in the impact of six ions, Na+, K+, Ca2+, Mg2+, Fe2+, and Fe3+, in the produced water from polymer flooding on the viscosity and stability of the polymer solution. Additionally, we provided the primary research methods for complexation in reinjected wastewater. Experimental results indicate that the main factors leading to a decrease in polymer viscosity are high-valence cations, with the descending order of their influence being Fe2+ > Fe3+ > Mg2+ > Ca2+ > Na+ > K+. High-valent cations also effect the viscosity stability of polymer solutions, and their order from greatest to least impact is: Fe2+ > Ca2+(Mg2+) > Fe3+ > Na+(K+). This article is focused on investigating the influencing factors and extent of the impact of oilfield wastewater on the viscosity of polymer solutions. It illustrates the response mechanism of cations to the viscosity of polymer solutions in reinjection wastewater polymerization. Through this research, the goal is to provide reference control indicators and limits for the water quality of injected polymers at oilfield sites. This ensures the stability and controllability of polymers in field applications and offers theoretical guidance for polymer flooding technology.