Thermo- and CO2-triggered swelling polymer microgels for reducing water-cut during CO2 flooding

CO₂ has been widely used in the process of enhanced oil recovery (EOR) over decades. However, the heterogeneity of oil reservoirs renders CO₂ to flow preferentially into highly permeable zones, leaving tight areas unswept with oil unrecovered in these areas. While conventional water-swelling gels were used for blocking the “channeling” path, most of them experience the risks of shrinkage under high temperature and CO₂-induced acidic environment. Here, we developed double swelling smart polymer microgels (SPMs) triggered by both heat and CO₂. Such SPMs were prepared by copolymerization of acrylamide (AAm) in combination with N,N-2-(dimethylamino)ethyl methacrylate (DMAEMA) and [2-(methacryloyloxy) ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA), and with N,N′-methylene bisacrylamide (MBA) as the crosslinker. These SPMs swell when temperature is higher than 65 °C or in the presence of CO₂, with an ameliorative salinity tolerance ability. Artificial sand pack flooding carried by SMPs at 65 °C showed an elevated plugging efficiency at around 97% under a simulated pressurization at 5 MPa, proposing a valid candidate for future EOR applications during CO₂ flooding. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48305.