Novel Green Strategy Based on Combination of CO₂/Protic Poly(ionic liquids) for Enhancing Crude Oil Recovery

Carbon dioxide (CO2) contributes to erratic climate changes as a greenhouse gas in the atmosphere, highlighting the need for effective carbon capture, storage, and conversion strategies. This study introduces a green solvent approach using protic poly(ionic liquids) (PPILs) for CO2 chemisorption to improve enhanced oil recovery (EOR) methods through gas/polymer flooding. The PPILs were synthesized by copolymerizing quaternized triethanolammonium 2-acrylamido-2-methylpropanesulfonate (QAMPS) with an equimolar amount of triethanol ammonium acrylate (QAA) via radical polymerization, resulting in QAMPS/QAA copolymers. Similarly, QAMPS was copolymerized with equimolar amounts of 2-hydroxyethyl methacrylate (HEMA) or N-vinylpyrrolidone (VP) to produce QAMPS/HEMA and QAMPS/VP protic PILs. The study examined the chemical structure, thermal degradation stability, and transitions. The thermal degradation of QAMPS/QAA, QAMPS/HEMA, and QAMPS/VP was obtained at initial degradation temperatures of 210, 275, and 150 °C, respectively. The rheological properties of these PPILs to assess their effectiveness in CO2 solubilization, absorption, and desorption at both atmospheric and high pressures (800 psi) in formation water for potential application in EOR gas/polymer flooding strategies were examined. Additionally, the research explores the dynamics of CO2 uptake by PILs and the ensuing alterations in their viscosity, which are crucial for enhancing the performance and success of EOR processes. Flooding on a 1D sandstone model revealed oil recovery rates of 38.9% for QAMPS/HEMA, 35.3% for QAMPS/VP, and 35% for QAMPS/QAA, relevant to residual oil saturation (%Sor).