Advanced oil recovery by high molar mass thermoassociating graft copolymers

Abstract

The chemical, thermal, and mechanical degradation of polymer chains under high salinity, temperature, and shear rates in oil reservoirs are the current challenges of the polymer flooding process. To answer such a complex requirement, recently, acrylamide (AM)-based thermoassociating graft copolymers (TAP) were synthesized that presented excellent performance as a viscosity enhancer, especially under high temperature and salinity conditions. The purpose of this study was to further investigate the effect of salinity, shear rate, mechanical strength, and adsorption of these TAPs on viscosity-enhancing performance at different temperatures. Finally, the performance of the TAPs was studied in oil recovery improvement, analyzed through the coreflooding experiments. The performance of novel copolymers was compared with an AM-based commercial copolymer. As a result of the clear thermoviscosifying effect of the TAPs, they presented much better performance in improving oil recovery at higher temperatures and salinities and much better mechanical resistance without increasing the polymer loss by adsorption on the rock surface within the reservoirs. Finally, the results of oil recovery confirmed the high applicability of the two TAPs because of their desirable features, resulting in a better mobility ratio and sweep efficiency under harsh reservoir conditions, a temperature up to 80 °C and a salinity about 200,000 ppm.