Preparation and evaluation of copolymers with rigid pendants for enhanced oil recovery in ultra-high temperature and high salinity reservoirs

There have been many reports on copolymers containing N-vinylpyrrolidone (NVP) or 2-acrylamide-2-methylpropanesulfonic acid (AMPS) that are temperature and salt resistant, while few works have been conducted on their potential for enhanced oil recovery (EOR) in super-high temperature (150 °C) and high salinity (10 × 10⁴ mg/L NaCl) reservoirs. The present work begins by introducing the properties of copolymers containing NVP or AMPS. Due to the reports’ main focus on the viscosity and long-term stability of copolymers under high temperature and high salinity conditions, the synthesis conditions for copolymers with rigid pendants (AMPS or NVP) are then optimized, followed by structural characterization. Following that, its comprehensive properties for enhanced oil recovery are examined. Experimental results manifested that the P(AM/AMPS) has better water solubility than P(AM/NVP). While P(AM/NVP) has superior viscoelasticity, salt resistance, and temperature resistance. In addition, P(AM/NVP) and P(AM/AMPS) have considerable EOR potential in ultra-high temperature and high salinity reservoirs, with EOR values ranging from 10.0 to 16.3%, particularly for the copolymer with NVP as a rigid pendant. The results indicated that copolymers with rigid pendants have potential application for enhanced oil recovery in ultra-high temperature and high salinity reservoirs.